Onan L Series L423 Engine Service Manual

934-0750 Onan L series (L317 L423 L634 L634T) Diesel Engine Service manual (06-1986) 934-0750 Onan L series (L317 L423 L634 L634T) Diesel Engine Service manual (06-1986)

User Manual: Onan-L-Series-L423-Engine-Service-Manual onan

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Service
Manual
L series

Diesel Engine

934-0750
6-86
Printed in USA.

Important Safety Precautions
Read and observe these safety precautions when using
or working on electric generators, engines and related
equipment. Also read and follow the literature provided
with the equipment.
Proper operation and maintenance are critical to performance and safety. Electricity, fuel, exhaust, moving parts
and batteries present hazards that can cause severe
personal injury or death.

FUEL, ENGINE OIL, AND FUMES ARE
FLAMMABLE AND TOXIC
Fire, explosion, and personal injury can result from improper practices.
Used engine oil, and benzene and lead, found in
some gasoline, have been identified by government
agencies as causing cancer or reproductive toxicity.
When checking, draining or adding fuel or oil, do not
ingest, breathe the fumes, or contact gasoline or
used oil.
Do not fill tanks with engine running. Do not smoke
around the area. Wipe up oil or fuel spills. Do not
leave rags in engine compartment or on equipment.
Keep this and surrounding area clean.
Inspect fuel system before each operation and periodically while running.
Equip fuel supply with a positive fuel shutoff.
Do not store or transport equipment with fuel in tank.
Keep an ABGrated fire extinguisher available near
equipment and adjacent areas for use on all types of
fires except alcohol.
Unless provided with equipment or noted otherwise
in installation manual, fuel lines must be copper or
steel, secured, free of leaks and separated or
shielded from electrical wiring.
Use approved, nonconductive flexible fuel hose for
fuel connections. Do not use copper tubing as a flexible connection. It will work-harden and break.

EXHAUST GAS IS DEADLY
Engine exhaust contains carbon monoxide (CO),
an odorless, invisible, poisonous gas. Learn the
symptoms of CO poisoning.
Never sleep in a vessel, vehicle, or room with a genset or engine running unless the area is equipped
with an operating CO detector with an audible
alarm.
Each time the engine or genset is started, or at least
every day, thoroughly inspect the exhaust system.
Shut down the unit and repair leaks immediately.

Warning: Engine exhaust is known to the State of
California to cause cancer, birth defects and other
reproductive harm.
Make sure exhaust is properly ventilated.
Vessel bilge must have an operating power
exhaust.
Vehicle exhaust system must extend beyond vehicle perimeter and not near windows, doors or
vents.
Do not use engine or genset cooling air to heat an
area.
Do not operate enginelgenset in enclosed area
without ample fresh air ventilation.
Expel exhaust away from enclosed, sheltered, or
occupied areas.
Make sure exhaust system components are securely fastened and not warped.

MOVING PARTS CAN CAUSE SEVERE
PERSONAL INJURY OR DEATH
Do not remove any guards or covers with the equipment running.
Keep hands, clothing, hair, and jewelry away from
moving parts.
Before performing any maintenance, disconnect
battery (negative [-I cable first) to prevent accidental starting.
Make sure fasteners and joints are secure. Tighten
supports and clamps, keep guards in position over
fans, drive belts, etc.
If adjustments must be made while equipment is
running, use extreme caution around hot manifolds
and moving parts, etc. Wear safety glasses and protective clothing.

BATTERY GAS IS EXPLOSIVE
Wear safety glasses and do not smoke while servicing batteries.
Always disconnect battery negative (-) lead first
and reconnect it last. Make sure you connect battery
correctly. A direct short across battery terminals can
cause an explosion. Do not smoke while servicing
batteries. Hydrogen gas given off during charging is
explosive.
Do not disconnect or connect battery cables iffuel
vapors are present. Ventilate the area thoroughly.

DO NOT OPERATE IN FLAMMABLE AND
EXPLOSIVE ENVIRONMENTS
Flammable vapor can be ignited by equipment operation
or cause a diesel engine to overspeed and become diff icult to stop, resulting in possible fire, explosion, severe
personal injury and death. Do not operate diesel equipment where a flammable vapor environment can be
created by fuel spill, leak, etc., unless equipped with
an automatic safety device to block the air intake and
stop the engine.
HOT COOLANT CAN CAUSE SEVERE
PERSONAL INJURY
Hot coolant is under pressure. Do not loosen the
coolant pressure cap while the engine is hot. Let the
engine cool before opening the pressure cap.
ELECTRICAL SHOCK CAN CAUSE SEVERE
PERSONAL INJURY OR DEATH
Do not service control panel or engine with unit running. High voltages are present. Work that must be
done while unit is running should be done only by
qualified service personnel.
Do not connect the generator set to the public utility
or to any other electrical power system. Electrocution can occur at a remote site where line or equipment repairs are being made. An approved transfer
switch must be used if more than one power source
is connected.
Disconnect starting battery (negative [-I cable first)
before removing protective shields or touching electrical equipment. Use insulative mats placed on dry
wood platforms. Do not wear jewelry, damp clothing
or allow skin surface to be damp when handling
electrical equipment.
Use insulated tools. Do not tamper with interlocks.
Follow all applicable state and local electrical
codes. Have all electrical installations performed by
a qualified licensed electrician. Tag open switches
to avoid accidental closure.
With transfer switches, keep cabinet closed and
locked. Only authorized personnel should have
cabinet or operational keys. Due to serious shock
hazard from high voltages within cabinet, all service
and adjustments must be performed by an electrician or authorized service representative.

If the cabinet must be opened for any reason:
1. Move genset operation switch or StopIAutol
Handcrank switch (whichever applies) to Stop.
2. Disconnect genset batteries (negative [-I lead
first).
3. Remove AC power to automatic transfer
switch. If instructions require otherwise, use
extreme caution due to shock hazard.

MEDIUM VOLTAGE GENERATOR SETS
(601V TO 15kV)
Medium voltage acts differently than low voltage.
Special equipment and training are required to work
on or around medium voltage equipment. Operation
and maintenance must be done only by persons
trained and qualified to work on such devices. Improper use or procedures will result in severe personal injury or death.
Do not work on energized equipment. Unauthorized
personnel must not be permitted near energized
equipment. Induced voltage remains even after
equipment is disconnected from the power source.
Plan maintenance with authorized personnel so
equipment can be de-energized and safely
grounded.
GENERAL SAFETY PRECAUTIONS
Do not work on equipment when mentally or physically fatigued or after consuming alcohol or drugs.
Carefully follow all applicable local, state and federal codes.
Never step on equipment (as when entering or leaving the engine compartment). It can stress and
break unit components, possibly resulting in dangerous operating conditions from leaking fuel, leaking exhaust fumes, etc.
Keep equipment and area clean. Oil, grease, dirt, or
stowed gear can cause fire or damage equipment
by restricting airflow.
Equipment owners and operators are solely responsible for operating equipment safely. Contact
your authorized OnanICummins dealer or distributor for more information.
KEEP THIS DOCUMENT NEAR EQUIPMENT FOR
EASY REFERENCE.

Safety Precautions
It is recommended that you read your engine manual and
become thoroughly acquainted with your equipment before
you start the engine.

Fud Systm
DO NOT fill fuel tanks while engine is running.
DO NOT smoke or use an open flame in the vicinity of the
engine or fuel tank Internalcombustionengine fuels ant
highly flamfnabl8.

I /

This symbd mlbn to a hazard or
~ n S 8 kpractice which can result in
severe personal iniury or death.

Thk symbol refers to a hazard or
unsafe practice which can result in
personal injury or product or p m W damage.
Fuels, electrical equipment, batteries. exhaust gases and
moving parts present potential hazards that can result in
serious, personal injury. Take care in following these recommended procedures.All local, state and federal codes should
be consulted and complied with.

I
to/
,or
any

Thh engine is not designed or inuse in
type of airera&
Use of this engine in aircraft can msullin engine failurn
and causer sodous personal injury or W t h .
Gonemi
Provideappropriate fire extinguishersand install them in
convenient locations. Use an extinguisher rated ABC by
NFPA.
Make surethat all fasteners on the engineare secureand
accurately torqued. Keep guards in position over fans
driving belts, etc.
If it is necessary to make adjustments while the engine is
running, useextreme caution when closeto hot exhausts.
moving parts, etc.
Prote~tA~MovingP~
Do not wear loose clothing in the vicinity of moving parts,
such as PTO shafts, flywheels, blowers, couplings, fans,
Wts. etc.
Keep your hands away from moving parts.

Battah
Before starting work on the engine, disconnect batteries
to prevent inadvertent starting of the engine.

DO NOT SMOKE while servicing batteria Lead acid
batteries give off a highly explosive hydrogen gas which
can be ignited by flame. dectrical arcing or by smoking.

Fuel lines must be of steel piping, adequately secured,
and free from leaks. Piping at the engine should be
approved flexible line. Do not use copper piping for
flexible lines as copper will work harden and become
brittle enough to break.
Be sure all fuel supplies have a positive shutoff valve.
Exhaust System
Exhaust products of any internal combustion engine are
toxic and can cause injury, or death if inhaled. All engine
applications. especially those within a confined area,
should be equipped with an exhaust system to discharge
gases to the outside atmosphere.

Do not use exhaust gases to heat a compartment.
Make sure that your exhaust system is free of leaks.
Ensure that exhaust manifolds are secure and are not
warped by bolts unevenly torqued.
Exhaust Gas h Dudlyl
Exhaust gases contain carbon monoxide, a poisonous gas
that can cause unconsciousnessand death. It is an odorless
and colorless gas formed during combustion of hydrocarbon
fuels. Symptoms of carbon monoxide poisoning are:
Dizziness
Headache
W
a M Sleepiness

Vomiting
Muscular Twitching
Throbbing in Temples

If you experienceany of these symptoms. get out into fresh air
immediately, shut down the unit and do not use until it has
been inspected.

The best protection against carbon monoxide inhalation is
proper installation and regular, frequent inspections of the
complete exhaust system. If you notice a change in the sound
or appearance of exhaust system. shut the unit down
immediately and have it inspected and repaired at once by a
competent mechanic.

codkr0a-n
Coolants under pressurehavea higher boilingpoint than
watetr. 00 NOT open a radiator pressure cap when
coolant temperature is above 212OF (lOO°C) or while
engine is running

Keoptheltnitmd~AnrCkan
Makesure that oily rags are not left on or near the engine.

Verify b a r n polarity before c o n n m battery cables

Remove all unnecessary grease and oil from the untt
Accumulated gre8se and oil can cause overheating and
subsequent engine damage and present a potential fire

Connectnegativecabiotast

haz8a

Foreword
This manual is designed to assist all service personnel with the maintenance and overhaul of Onan L series
dieselengines. It presents a description of each systems function together with instructions on servicing and
overhaul procedures. A DIMENSIONS AND CLEARANCES SECTION is provided and must be closely
followed when overhauling or servicing any part of engine.
Unless otherwise specified the information applies to all L diesel engines. Where information applies to a
specific engine it is so noted.
These engines have a counterclockwise rotation when viewed from the rear, flywheel end of engine.
Throughout this manual, "right-handMand"left-handMsidesare determined by facing the drive end (flywheel)
of engine.
The manner in which the engine is operated and the maintenance performed on it will determine its
performance, safety, and durability. Equally important is the use of proper procedures during engine overhaul. Before operating, servicing, or beginning an overhaul, read this manual carefully to familiarize yourself
with the engine procedures involved, and the tools required. Keep this manual handy and refer to it often.
This manual is divided into 11 SECTIONS covering the topics listed on the CONTENTS page. At the
beginning of each SECTION is an index of the subjects covered. Pages are numbered consecutively,
beginning with a new Page 1 at the outset of each SECTION. Each page number is preceded by the
appropriate reference number for that SECTION. All illustrations are numbered consecur~vely,beginning
with a new Figure 1 in each SEC'TION.

Always give complete MODEL and SERIAL NO. of engine being serviced when ordering replacement parts.

Contents
SECTION AND TITLE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.

Specifications
Dimensions and Clearances
Torques
Special Tools
Troubleshooting
Start-Up
Maintenance
Oil System
Cooling System
Fuel System
Exhaust System
Electrical System
Engine Disassembly
Turbocharger

!-GziGZl
INCORRECT SERVICE OR REPLACEMENT OF PARTS CAN RESULT IN
SEVERE PERSONAL lNJURY AND/OR EQUIPMENT DAMAGE. SERVICE
PERSONNEL MUST BE QUALIFIED TO PERFORM ELECTREAL AND/OR
MECHANICAL SERVICE.

1. Specifications
SUBJECT

. . .

. ......-1-1
.. .. .......-1-5

ENGINE . . .. .. . . .. . . . . . . . .... . . . .. . . . . . . . . .. . . ..., . ...... . .. .
STATIC PUMP TlMlNG ....... .. . . .......... . . ... ....... . .. .

PAGE

INDUSTRIAL ENGINE
SPECIFICATION

Number of Cyl~nders
Diesel Fuel
Bore
Stroke
Displacement
Compression Ratio
Rated Speed (Maximum)
Power (rntermrttent) at
Rated Speed'
Power (continuous) at
Rated Speed'
Firing Order
Crankshaft Rotation
(viewed from flywheel)
Governor
Valve Lash (Spec A to C) +
Intake

Exhaust
Oil Filter
Crankcase Capacity
with filter change

UNIT OF
MEASURE

mm
(in)
mm
(in)
litre
(cu in)
RPM
kW
(BHP)
kW
(BHP)

mm
(in)
mm
(in)
litre
(qt)

L SERIES
L317

L423

L634

L634T

3
4
ASTM2-D
ASTM2-D
89
89
(3.50)
(3.50)
92
92
(3.62)
(3.62)
1.7
2.3
( 140)
(105)
21.5 to 1
21.5 to 1
3600
3600
31.3
43.3
(42.0)
(58.0)
28.5
39.4
(38.0)
(52.7)
132
1243
- Counter
Counter
Clockwise
Clockwise
Variable Speed Mechan~cal

6
6
ASTM2-0
ASTM2-D
89
89
(3.50)
(3 50)
92
92
(3.62)
(3.62)
3.4
3.4
(210)
(210)
21.5 to 1
21 5 t o 1
3600
3600
65.0
85.8
(87.0)
(115.0)
59.1
78.0
(104 5)
(79.1)
153624
153624
Counter
Counter
Clockwise
Clockwise
Variable Speed Mechanical

0.20
(0.008)
0.30
(0.012)
Full Flow
5.7
(6)

0.20
(0.008)
0.30
(0.012)
Full Flow
8.5
(9)

0.20
(0.008)
0.30
(0.012)
Full Flow
5.7
(6)

0.30
(0.012)
0.30
(0.012)
Full Flow
11.4
(12)

All dtmensions ~nmetr~c(U S customary units of measure ~nparentheses) unless otherw~sespecified
- Power obtained and corrected tn accordance with SAEJ1349 [I00kPa (29 61 ~nchesHg) barometric pressure at 2S°C (77°F) alr tnlet
temperature] wtthout air cleaner. fan, and exhaust muffler on naturally aspirated englnes
Power losses for typlcal air cleaner and muffler tnstallations ~ncludedon turbocharged engtnes
Begtnn~ngSpec 0 no valve lash adjucmnerrt requtred.

MARINE ENGINE
UNIT OF
MEASURE

SPECIFICATION
Number of Cylinders
Diesel Fuel
Bore
Stroke
Displacement
Compression Ratio
Rated Speed (Maximum)
Power (intermittent) at
Rated Speed*
Power (continuous) at
Rated Speed'
Firing Order
Crankshaft Rotation
(viewed from flywheel)
Governor
Valve Lash (Spec A to C)
Intake

L SERIES
L317D-M
L4230-M
3
ASTM2-D

4
ASTM2-D

(in)
mm

(3.50)
92

litre
(cu in)

1.7
( 105)

RPM
kW
(BHP)

21.5 to 1
3600
32.4
(43.5)

2.3
(140)
21.5 to 1
3600
44.7
(60.0)

29.5
(39.5)
132
Counter
Clockwise

40.7
(54.5)
1243
Counter
Clockwise

kW
(BHP)

Variable Speed Mechanical

Exhaust
Oil Filter
Crankcase Capacity
with filter change
Coolant Capacity
with heat exchanger

mm
(in)
mm
(in)
litre
(9t)
litre
(qt)

0.20
(0.008)
0.30
(0012)
Full Flow
5.7
(6)
6.8
(7.2)

All dimensions in metric (US. customary units of measure in parentheses) unless otherwise specified.
Power obtained with 100 kPa (29 .92 inchw Hg) barometric pressure at 1S0C (60°F)air inlet
temperature without air cleaner or exhaust muffler.
Beg~nntngSpec D no valve lash adjustment required.

0.20
(0.008)
0.30
(0.012)
Full Flow
5.7
(6)
9.1
(9.6)

POWER UNlT
SPECIFICATION

UNIT OF
MEASURE

L423

L SERIES
L634

4
ASTM2-D

6
ASTM2-D

litre
(qt)

0.20
(0.008)
0.30
(0.012)
Full Flow
5.7
(6)

0.20
(0.008)
0.30
(0.012)
Full Flow
8.5
(9)

0.30
(0.012)
0.30
(0.012)
Full Flow
11.4
(12)

litre
(qt)
litre
(qt)

13.1
(13.9)
13.5
(14.2)

16.6
(17.5)
17.1
(18.1)

17.1
(18.1)

Number of Cyl~nders
Dtesel Fuel
Bore
Stroke
Displacement

compresslon Ratlo
Rated Speed (Maximum)
Power (intermittent) at
Rated Speed*
Power (continuous) at
Rated Speed*
Firlng Order
Crankshaft Rotation
(v~ewedfrom flywheel)
Governor
Valve Lash (Spec A to C) '
Intake
Exhaust
Oil Filter
Crankcase Capacity
wlth fllter change
Cooling System Capacity
Englnes w~thout
oil cooler
Englnes wlth
oil cooler

mm
(in)
mm
(in)
litre
(CU~ n )
RPM
kW
(BHP)
kW
(BHP)

mm
(in)
mm
(in)

L634T

6
ASTM2-D
89
89
89
(3.50)
(3.50)
(3.50)
92
92
92
(3.62)
(3.62)
(3.62)
2.3
3.4
34
(140)
(210)
(210)
21.5 to 1
21.5 to 1
20.5 to 1
2600
3600
3200
33.9
59.7
80.2
(45.5)
(80.0)
(107.5)
30.9
54.2
72.9
(41.4)
(72.7)
(97.7)
1243
153624
153624
Counter
Counter
Counter
Clockwise
Clockw~se
Clockwlse
Var~ableSpeed Mechan~cal

All dlmens~onsIn metrlc (US. customary un~tsof measure in parentheses)unless othemlse specified.
*
Power obta~nedand corrected in accordance wlth SAW1349 [I00 kPa (29.61 Inches HG) barometr~cpressure at 2S°C (77°F) alr Inlet
temperature], wlth air cleaner and fan.
Beglnn~ngSpec 0 no valve lash adjustment required.

AUTOMOTIVE ENGINE
UNIT OF
MEASURE

SPECIFICATION
Number of Cylinders
Diesel Fuel
Bore

mm
(in)
mm
(in)
litre
(CU in)

Stroke
Displacement
Compression Ratio
Rated Speed (Maximum)
Power at
Rated Speed*
Firing Order
Crankshaft Rotation
(viewed from flywheel)
Governor
Valve Lash (Spec A to C) +
Intake
-

Exhaust
Oil Filter
Crankcase Capacity
with filter change

RPM
kW
(BHP)

mm
(in1
mm
(in)
litre

(@)

L SERIES
L634T-A
6
ASTM2-D
89
(3.50)
92
(3.62)
3.4
(210)
20.5 to 1
2800
3600
83.5
89.5
(112.0) (120.0)
153624
Counter
Clockwise
Min.-Max.
0.30
(0.012)
0.30
(0.012)
Full Flow
Refer to
Engine Nameplate

All dimensions in metric (U.S. customary units of measure in parentheses) unless otherwise 3pecified.

Power obtatned and corrected in accordance with SAEJ1349 1100 kPa (29.61 inch- HG) barometric pressure at 25OC (77'F) alr lnlet
temperature], without fan.
Power losses for typical air cleaner and muffler installations included on turbocharged engnes.
Refer to engine nameplats for rated speed and powof.
Beg~nningSpec 0 no valve lash adjumemt required.

STATIC PUMP TIMING SPECIFICATIONS
I n February 1983 a change Was made in the internal timing of the fuel injection pump and to the pump part
numbering system. AS a result of these changes, it may be necessary to change the engine static timing when
installing a replacement fuel injection pump.
~ 1 fuel
1 injection pumps built before February 1983 are marked with a seven digit (Example: 147-0453) Onan part

number. Fuel injection pumps built after February f983are marked with a ninedigit (Example: 147-0462-02) Onan
pafinumber, The Onan part number is stamped On the injection pump name plate. Engine performance is the

same for both injection pumps when engtne static timing is correctly set.
Find the seven or nine digit Onan part number stamped on the replacement pump and refer to Table 1 for the
correct static timing specification.
Refer to SECTION 10, FUEL SYSTEM for complete fuel injection pump installation instructions.

TABLE 1. STATIC PUMP TIMING SPECIFICATIONS
Replacement Pump

Original Pump

Static Timing

9 digit
9 digit

7 digit
9 digit

7 digit

9 digit

7 digit

15' BTDC* All Engine applications.
15' BTDC All engine applications. No change to
engine model label required.
14.5' BTDC* 4 cylinder (700-3600 rpm)
15' BTDC* 6 cylinder (700-3600 rpm)
19' BTDC* 4 and 6 cylinder (1500 and 1800 rpm)
Refer to engine model !abel for correct static
timing specification.

'Change static timing specification on engine model label.

2. Dimensions and Clearances
SUBJECT
DIMENSIONS AND CLEARANCES

PAGE

. . . . . . ... . ... . . . . . .. .. . . . . . . . . . . . . . . . . . 2-1

DIMENSIONS AND CLEARANCES

All clearances given at room temperature of 21°C (7o0F). All dimensions in millimetre~~approximate
inch dimensions in
parentheses) unless otherwise specified.
Maximum allowablewear limit of a part is the point at which its proper function becomes impaired. Even though parts are still
within the specified wear limits at time of rebuild, other considerations should also be used in evaluating the parts continued
use.

IPCAUTIONI

Metric measuring tools, metric dimensions, and clearances must be used when servicing the
onan L Engine. The use ot inch measuring tools and approximate inch dimensions and
clearances will cause stack up tolerances to be greater than specified.

DIMENSION
OF
NEW PARTS
millimetre
(inch)

DESCRIPTION

CYLINDER BLOCK
Cylinder Bore Honed Diameter .............. 88.987-89.013 (3.5034-3.5044)
Cylinder Bore Out-of-Round
Cylinder Bore Taper
Main Bearing Bore (Cap in place without bearing,
and capscrews properly torqued.) .......... 80.880-80.906 (3.1843-3.1853)
Main Bearing Bore (Bearings installed and
capscrews properly torqued.) .............. 76.040-76.090 (2.9937-2.9956)
Undersize Main Bearings (Available for
N.A. Engines Only). ..................... 0.25 mm, 0.50 mm, and 0.75 mm
Camshaft Bearing Bore (Without bearing) .... 53.164-53.188 (2.0930-2.0940)
Camshaft Bearing Bore (Bearing installed) ... 50.044-50.1 16 (1.9702-1.9730)
Valve Tappet Bore

.......................... 26.070-26.1 00 (1.0263-1.0276)

CRANKSHAFT
Main Bearing Journal Diameter

................ .75.99-76.01 (2.9917-2.9925)

Main Bearing Clearance ..........................0.03-0.10 (0.0012-0.0039)
Main Bearing Journal Out-of-Round ........................ 0.007 (0.0003)
Main Bearing Journal Taper ................................0.005 (0.0002)
Connecting Rod Journal Diameter ..............55.99-56.01 (2.2043-2.2051)
Connecting Rod Journal Out-of-Round.. .................... 0.005 (.0.0002)
Connecting Rod Journal Taper ............................. 0.005 (0.0002)
Crankshaft End Play ............................ .0.10-0.33 (0.0039-0.01 29)
Crankshaft Straightness Runout of Center Main.. ............. 0.05-(0.0019)

CONNECTING ROD
Large Bearing Bore to Small Bearing Bore
(Center-to-Center) ...................... 155.975-156.025
Large Bore Diameter (Without bearing installed
and rod nuts properly torqu,&. ............. 59.860-59.875
~earing"toCrankshaft Cleafgktce. ..:,......:... .0.030-0.091
Connecting Rod Side Clearance .: ............... .0.05-0.45
Piston Pin Bushing Bore (Without bearing) ..... .35.20-35.23
Piston Pin Bushing Bore with Bearing,
(Finished bore) :..............................32.01-32.02

80 .906
See main bearing
journal clearance
53.188
See camshaft
bearing clearance
See valve tappet
clearance in bore
See main bearing
journal clearance
0.15
0.010
0.007
See connecting rod
bearing-to-crankshaft
clearance
0.007
0.007
0.38
0.10

(6.1407-6.1427)
(2.3567-2.3572)
(0.0012-0.0036)
(0.0019-0.0177)
(1.3858-1.3870)
(1.2602-1.2606)

Large Bore Diameter (With bearing installed and
rod nuts properly torqued). ................ 56.040-56.081 (2.2063-2.2079)
Undersize Connecting Rod Bearings (Available for
N.A. Engines Only).
0.25 mm, 0.50 mm, and 0.75 mm

.....................

MAXIMUM
ALLOWABLE
WEAR LIMIT
millimetre

59.875
0.1 5
($45
35.23
See clearance
connecting rod
bushing
See connecting rod
bearing-to-crankshaft
clearance

MAXIMUM
ALLOWABLE
WEAR LIMIT
millimetre

DIMENSION
OF
NEW PARTS
millimetre
(inch)

DESCRIPTION

CAMSHAFT
Bearing Journal Diameter ......................49.988-50.014 (1.9680-1.9691)
Bearing Clearance .............................. 0.030-0.1 27 (0.0011-0.0050)
End Play ..........................................0.10-0.50 (0.0039-0.01 97)
Journal Runout ............................................... 0.05 (0.0019)
Intake and Exhaust Lobe, Base-to-Tip
(Spec A to C) ................................. 42.95-43.1 5 (1.6909-1.6988)
Intake Lobe, Base-to-Tip (Begin Spec D) .......... 42.56-42.86 (1.6756-1.6874)
Exhaust Lobe, Base-to-Tip (Begin Spec D) ......... 42.86-43.1 6 (1.6874-1.6992)
PISTON
Clearance in Cylinder (Measure 90' to pin, 13 mm below oil ring)
Naturally Aspirated Engines .................... 0.145-0.201 (0.0057-0.0079)
Turbocharged Engines ......................... 0.137-0.1 93 (0.0054-0.076)
Diameter (Measure 90' to pin, 13 mm below oil ring)
Naturally Aspirated Engines .................. 88.812-88.842 (3.4965-3.497 7)

...................... 88.820-88.850 (3.4969-3.4980)
Piston Pin Bore ................................32.003-32.009 (1.2599-1.2601
Turbocharged Engines

See camshaft bearing
clearance
0.1 50
0.70
0.10

See piston to
cylinder clearance
See piston to
cylinder clearance
See piston pin
clearance in piston

Ring Groove Width
Top 1 Compression Ring.. ....................... .2.04-2.10 (0.0803-0.0827)
No. 2 Compression Ring ......................... .2.54-2.56 (0.1000-0.1 007)
No. 3 Oil Control Ring ............................4.04-4.06 (0.1590-0.1 598)
*Top 1 Compression Ring Groove
Dimension over 2.60 mm diameter
gauge wire.. ................................. 88.13-88.33 v.4697-3.4776)
*No. 2 Compression Ring .........................2.59-2.61 (0.1019- 0.1028)
PISTON PIN
Clearance in Piston ............................. 0.003-0.014 (0.0001 -0.0005)
0.010-0.025 (0.0004-0.0010)
Clearance, Connecting Rod Bushing
Diameter
31.995-32.00 (1.2596-1.2598)

..............
......................................

PISTON RINGS
Clearance
Top Groove
*Top Groove Ring Drop

.................................... .0.05-0.13

........................ 0.027-0.52

(0.001 9-0.0051)
(0.0011-0.0205)

................................... .0.05-b.e (0.0419-0.0035)
.......................0.10-.0.14 ( 0 . w - 0 . w )
.................................. 0.050-0.095 (0.0019-0-0037)
............................. .0.31-0.57 (0.0-122-0.02a...............................0.3 -0.57 (0.01 22-0.0224)
........................................0.22-0.58 (0.0087-0.0228)
.......................... 0.25mm, QSOmm, 0.75mm. and l.Omm

2nd~ r o o v e
*2nd Groove ............r
Oil eoove
End Gap
Top 1 Compression
No.2 Compression
No. 3 Oil
Oversize Pistons and Rings Available
for Service
/-

Turbocharged engine.

0.03
0.05
See clearance,
connecting bushing

-.-,

025

Seb piston.top.

groove dimension
0.25

DIMENSION
OF
NEW PARTS
millimetre
(inch)

*Stem Diameter..

..............................

.7.95-7.97 (0.3130-0.3138)

clearance (Stem to Guide) .......................0.04-0.08 (0.0016-0.0031)
'Clearance (Stem to Guide) .................... .0.02-0.06 (0.0008-0.0024)
Clearance (Lash) (Spec A to C) ................................. 0.20 (0.0078)
*clearance (Lash) (Spec A to C) ............................... 0.30 (0.0118)
TOP of Valve Recessed
Below Cylinder Head Deck ..................... 0.48-1.1 3 (0.0189-0.0445)
valveFace Angle .................................................... 2g0

MAXIMUM.
ALLOWABLE
WEAR LIMIT
millimetre
See stem to
guide clearance
See stem to
guide clearance
0.16
0.14
Adjustable
Adjustable

INTAKE VALVE SEAT INSERT
Seat Insert Cylinder Head Bore Diameter ....... .40.30-40.32 (1.5866-1.5874)
Seat Insert Cylinder Head Bore Depth ..............8.40-8.50 (0.3307-0.3346)
Seat InsertOutside Diameter ...................40.37-40.40 (1.5894-1.5906)
Valve Seat Width .................................0.88-2.30 (0.0346-0.0906)
Valve Seat Angle ..................................................... 30°
Valve Seat Runout ..........................................0.05 (0.0019)
Available Insert Sizes.. .....................Std., 0.25mm, and 0.50 oversize
Naturally aspirated engines do not have intake valve seat inserts.
EXHAUST VALVE
Stem Diameter. ..................................7.93-7.95 (0.3122-0.31 30)
Clearance (Stem to Guide) ...................... .0.04-0.08 (0.0016-0.0031 )
Clearance (Lash) (Spec A to C) ................................ 0.30 (0.011
Top of Valve Recessed
below Cylinder Head Deck .................... .0.67-1.33 (0.0264-0.0524)
Valve Face Angle ....................................................44O
EXHAUST VALVE SEAT INSERT
Seat Insert Cylinder Head Bore Diameter
.36.93-36.95 (1.4539-1.4547)
Seat Insert Cylinder Head Bore Depth ............ .8.49-8.59 (0.3342-0.3381)
Seat Insert Outside Diameter
.37.00-37.03 (1.4567-1.4579)
Valve Seat Width..
:-.
;
.0.88-2.30 (0.0346-0.0906)
Valve Seat Angle..
45'
Valve Seat Runout
0.05 (0.0019)
Available Insert Oversize
.0.25 and 0.50mm

.......
..................
....... .........,.. .......
....................................................
...........................................
................................

. .
VALVE GUIDE
Length
lntake
.56.5-57.3 (2.2244-2.2560)
Exhaust
-1.. .62.5--63.3 (2.4606-2.4921 )
Inside Diameter (after reaming)
Intake
.7.99-8.01 (0.3146-0.3154)
.7.99-8.01 (0.3146-0.3154)
Exhaust
Height Above Counterbore
15.6-16.4 (0.6142-0.6457)
Without Valve Rotators (Spec A & 6)
(i Without Valve Rotators (Begin Spec C)
14.8-15.6 (0.5827-0.6142)
With Valve Rotatem or Spacer (Begin Spec C) .22.3-23.1 (0.8779-0.9094)
Valve guides in new and factory service heads do not require reaming.

........................................
............................... ...

........................................
............................,., ........
.............
..........
..

' Turbocharged engine.

See stem to
guide clearance
0.16
Adjustable

DESCRIPTION

DIMENSION
OF
NEW PARTS
millimetre
(inch)

TAPPET
Body Diameter (Spec A to C)

................... 26.000-26.01 5 (1.0236-1.0242)
Body Diameter (Begin Spec D). ................. 26.027-26.043 (1.0247-1.0253)

Overall Length (Spec A to C) ..................... 50.00-50.50 (1.9685-1.9882)
Clearance in Bore (Spec A to C) .................. 0.055-0.100 (0.0022-0.0039)
Clearance in Bore (Begin Spec 0). ................. 0.043-0.057 (0.0016-0.002)

MAXIMUM
ALLOWABLE
WEAR LIMIT
millimetre
See tappet clearance
in bore
See tappet clearance
in bore

0.1 50
0.1 25

VALVE SPRINGS INTAKE AND EXHAUST
Valve Spring Free Length (Approx.) ............................. .51.0 (2.0)
Valve Spring Length
Valve Open ................................................. .32.8 (1.29)
Valve Closed ............................................... .42.5 (1.67)
Spring Load @ 42.5 mm (Valve Closed). ............. 29.2-31.2 kg (64-69 Ib)
Spring Load @ 32.8 mm (Valve Open) ............. 62.7-66.7 kg (138-147 Ib)
GEAR BACKLASH
Crankshaft to Idler ............................ .0.050-0.223 (0.0019-0.0087)
Idler to Camshaft ............................. .0.045-0.264 (0.0017-0.0104)
Idler to Injection Pump .........................0.075-0.326 (0.0030-0.0128)
Oil Pump Idler to Crankshaft.. ................. .0.041-0.256 (0.0016-0.0101)
Oil Pump Idler to Oil Pump Drive.. ..............0.044-0.262 (0.0017-0.0103)
Oil Pump Element Gears ...................... .0.076-0.430 (0.0029-0.0169)
CYLINDER HEAD
Flatness (In 150.0 mm [5.91] of length)

....................... 0.03 (0.0012)

IDLER GEAR ASSEMBLY OIL PUMP
Bearing Bore ............................... 25.030-25.054 (0.9854-0.9863)
Idler Gear Shaft Diameter

................... 24.986-25.000 (0.9837-0.9842)

Bore to Shaft Clearance ........................0.030-0.068 (0.0012-0.0027)
End Play .......................................... 0.05-0.25 (0.002-0.010)

IDLER GEAR ASSEMBLY CAM AND INJECTION PUMP
Bearing Bore ............................... 40.030-40.054 (1.5760-1.5770)

................... 39.98640.000 (1.5742-1.5748)
Bore to Shaft Clearance ....................... .0.030-0.068 (0.0012-0.0027)
End Play ....................................... .0.15-0.35 (0.0059-0.0138)
Idler Gear Shaft Diameter

INJECTION NOZZLE
Opening Pressure
New'Nozzle Tip and Spring ............ 13,000-1 3.800 kPa (1890-2000 psi)
'Opening Pressure
New Nozzle Tip and Spring ............ 17.000-17,800 kPa (2470-2580 psi)

See bore to
shaft clearance
See bore to
shaft clearance
0.100
0.30

See bore to
shaft clearance
See bore to
shaft clearance
0.100
0.40

$11,,000 kPa
$13,800 kPa

$ Nozzle opening pressure between cylinders must not vary more than f600kPa (87 psi).
' Turbocharged engine

DIMENSION
OF
NEW PARTS
(inch)
millimetre
OIL PUMP BODY
Shaft Bore Diameter
Idler ..................................... 11.918-1 1.942 (0.4692-0.4702)
Drive ..................................... 11.918-1 1942 (0.4692-0.4702)
pump Gear Bore Diameter.. ................... .35.69-35.74 (1.4051-1.4071)

pump Gear Bore Depth
L317, L423. ..................................15.07-15.12 (0.5933-0.5953)
L634 ........................................24.07-24.12 (0.9476-0.9496)
L634T .......................................32.07-32.12 (1.2626-1.2646)
OIL PUMP SHAFTS
Diameter
Drive-in Body ............................. 11.888-11.902 (0.4680-0.4686)
Drive-in Bushing .......................... 15.986-16.000 (0.6294-0.6299)
Idler

.....................................

11.955-11.970 (0.4707-0.4713)

Drive Shaft Clearance in Body ..................0.016-0.054 (0.0006-0.0021)
Drive Shaft Clearance in Bushing .............. .0.017-0.103 (0.0007-0.0041)
Idler Shaft Clearance in Gear .................. .0.016-0.045 (0.0006-0.0018)
OIL PUMP GEARS
Inside Diameter (Both)

......................

11.986-12.000 (0.4719-0.4724)

.................... 35.474-35.500 (1.3966-1.3976)
Radial Clearance in Body Bore.. ................0.095-0.133 (0.0037-0.0052)
End Clearance to Body .........................0.056-0.134 (0.0022-0.0053)
Gear Length (Both)
3 and 4 Cylinder N.A.. ........................14.986-15.014 (0.59-0.5911)
6 Cylinder N.A. ........................... 23.986-24.01 4 (0.9443-0.9454)
Outside Diameter (Both)

6 Cylinder Turbocharged

.................. 31.986-32.014 (1.2592-1.2604)

TURBOCHARGER
Holset
End Play ........................................
Radial Play ......................................
Ai research
End Play ........................................
Radial Play ......................................

0.1 0-0.16 (0.004-0.006)
0.30-0.46 (0.012-0.018)
0.03-0.08 (0.00 1-0.003)
0.08-0.1 5 (0.003-0.006)

MAXIMUM
ALL0 WABLE
WEAR LIMIT
millimetre

11.97
See oil pump gear
radial clearance
in body bore
See oil pump
gear end clearance
to body

See drive shaft
clearance in body
See drive shaft
clearance in bushing
See idler shaft
clearance in gear
0.07
0.15
0.060

See ldler shaft
clearance in gear
See clearance
in body bore
0.175
0.150
See end
clearance
to body

3 Torques
SUBJECT

PAGE

ENGINE ASSEMBLY TORQUES .................................. 3-1
INJECTION PUMP TORQUES .................................... 3-2

ENGlNE ASSEMBLY TORQUES

The torque values given in Table 1 have been determined for the specific applications. Standard torque
values mus: not be used where those listed in Table 1
and Figure 1 apply. The engine assembly torques given
here will assure proper tightness without danger of
stripping threads. All threads must be clean and
lubricated with new engine oil before torquing. Proper

Joint Design Practices were utilized that do not require
lockwashers or gaskets. Do not attempt to use lockwashers with these bolts, it will defeat their purpose.
Check all studs, nuts, and capscrews, and tighten as
required to keep them from working loose. Refer to the
PARTS MANUAL for the location of washers and
capscrews.

TABLE 1.
L

All torque8 are in Newton-Melre, Nm (approximatetoot-pound
toques, Ft.-Lb., in parentheses) unless othorwiiw specilkd.

DESCRIPTION
Matn Bearing Cap
Connect~ngRod
Rear Seal Plate
Backplate (Gearcase)
Camshaft Retamer
011Pump
Idler Gear
Pump Idler
Pump Dr~ve
Gearcase
Gearcase
Iron1Pulley
9.Ftywheel Housing

Flywhee4
011Ptckup Brace
Turbocharger
011Pan
Cyltnder Head
Rocker Studs
Water Pump Cover
Water Pump
Water Pump Plugs
Thermostat Cover
In~ectton
Pump

TORQUE
SPEClFlCATlON
Nm
Ft.-Lb.

SIZE

CUSS

12
10
8
8
8
8
10
8
8
8
12
16
12

109
129
88
88
88
88
88
88
88
8.8
8.8
8.8
8.8

123
85
23
23
23
23
52
23
23
23
64
1
84

(90)
(63)
(17)
(17)
(17)
(17)
(39)
(17)
(17)
(17)
(62)
(62)

Flangehead Capscrew
Exhaust Stack
Water Pump Pulley

10
8
10
8
12
10
6
8

10.9
8.8

68
23
52
11
129
52
11
23

(50)
(17)
(39)

Alternator Bracket
Alternator Pivot
Alternator Adj

(a31

Smter

(95)
(39)
(8)
(17) '
(12)
(17)
(17)

011Filter Adapter
Fud Ftlter Mounting
Transfer Pump
Glow Pfuga
Injection bne Nuts
Oil Coder
Rocker Nut Locknuto*
Rocker Cove Cap Nut

8.8
10.9
8.8
8.8
8.8

8
8

8.8
8.8

23
23

(98)

DESCRIPTION
Inpcbon Pump Gear
Stanadyne Pump
Bosch Pump
Gear Cover
Injectton Noule
Assembly
Installation
Intake Man~fold
Exhaust Mantfold*
Caprcrew and Flatwasher

*Exhaust capcrews must be torqued In the p r o w ~ O U W ~toO P m t
wupn~
of exhaust manand posstble kaka!p ot exhaust WsOS.
**This toque 1s due to fncnon between the threads only and locks the nut In
place. Use the rocker arm, nut to adjust valve lash.
Y
I

SIZE

14
14
8
22
24
8
8
8
10
8
8
10
8
12
8
10
6
12
12
8
15
10

CUSS

TORQUE
SPECIFICATION
Nm
Ft.-Lb.

52
80

(38)
(58)

(17)

69
69
23

(51)
(51)
(17)

(21)

35
52
23
23
52
23
84
23
30
11
19
24
23
34
18

(26)
(39)
(17)
(17)
(39)
(17)
(62)
(17)
(22)
(8)
(14)
(18)
(17)
(25)
(13)

88
88
88
88
88
88
88
88
88

129
109

STANADYNE
INJECTION PUMP 1ORQUES
All t0qu.r in Newton-Metm (inch-pound In pmntheses) unless otherwise s p ~ i f i d .

'41-50 Nm

(m
IN.4
(See Note)

'Critical Torque Values
Note: Apply Lubriplate (630AA) to Chamfer
of pressure plate and cap threads.

FIGURE 1. FUEL INJECTION PUMP TOROMS

4. Special Tools
SUBJECT
SPECIAL TOOLS..

PAGE

. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . 4-1

SPECIAL TOOLS
The following special tool listing was prepared to aid service and maintenance personnel in obtaining the proper
tools to accomplish the various service and maintenance operations described and illustrated in this manual.
The special tools listed below are available from Onan to aid service and repair work .
Diesel Nozzle Tester ............................................................................420-0184
Diesel Pintle Nozzle Cleaning Tool Set ...........................................................420-0208
Deep Socket 27mm 112" Drive (Injection Nozzle) ................................................. 420-0425
crowfoot Wrench 17mm 318" Drive (High Pressure Line Nuts) ..................................... 4 20-0426
Gear Puller Kit Injection Pump and Front Crankshaft Pulley ....................................... 4 20-0427
Socket. Transfer Pump Removal .................................................................420-0429
Injection Pump Tools. Stanadyne
shutoff Cam Removal Tool ...................................................................420-0430
Throttle Shaft Seal Spreader ..................................................................420-0431
~dvancePlug Wrench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2
0-0432
Socket Driver (End Cap Locking Screw) .......................................................420-0433
lntakeValveSeatDriver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2
0-0421
Exhaust Valve Seat Driver .......................................................................420-0420
valve Spring Compressor
420-01 19
valveseat Remover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2
0-0436
Valve Guide Removal Tool
420-0443
Valve Guide Installation Tool
-420-OW
ValveGuideReamer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2
0-0439
Valve Seat Concentricity Indicator
420-0437
Rear Oil Seal Driver-Wear Sleeve Installing Tool
420-0417
Engine Application Test Kit
420-0434
Engine Stand Mounting Plate (&cylinder)
420-0424
Engine Stand
420-0441
Front Wear Sleeve Oil Seal Installing Tool
420-0418
Cam Bearing Puller
4204428
Cam Bearing Puller (Head only)
-4204422
CylinderLeakageTester
4204343
Oil Cooler Test Fixture
-420-0435
Fan BeltTensionTool
42G0438
Valve Rocker Stud Socket
4204423
Onan Tool Catalog
-900-0019

.......................................................................
......................................................................
...................................................................
...............................................................
..................................................
.....................................................................
........................................................
..................................................................................
......................................................
.............................................................................
................................................................
........................................................................
........................................................................

5 Troubleshooting
SUBJECT

PAGE

ENGINE
5-1
5-5
CYLINDER LEAK DOWN TEST PROCEDURE
ELECTRICAL SYSTEM
5-6
FUEL SYSTEM
5-7
COOLING SYSTEM
5-8
OIL SYSTEM .............................................................
5.9
TURBOCHARGER ......................................................5-10

Most of the troubles that occur in engine operation
can be avoided when those responsible for engine
maintenance adhere to an adequate program of lubrication, inspection and maintenance. The time and
expense involved in a good maintenance and inspection program is only a small portion of that incurred
when poor maintenance practice results in a major
malfunction or breakdown.

In most instances, when a problem is detected and
fixed immediately,a more expensive, time consuming
repair will be avoided. The following list of troubles.
causes and remedies is supplied to aid the operator/
service person in locating and correcting mechanical
and electrical troubles as soon as possible. For specific inspection and service procedures for any given
component, refer to that section or subject in this
manual pertaining to the part, assembly or system.

ENGINE
TROUBLE
Engine will not turn or
crank

POSSIBLE CAUSES
1. Batteries weak.

2. Starter or starter switch
inoperative.
3. Engine locked or seized.

4. Hydro-static lock.

1. Slow cranking speed.

2. Glow plugs.
3. Engine controls out of
adjustment.
4. Insufficient supply of fuel to
injection nozzles.
5. Injection nozzles not operating
Properly6. Incorrect valve lash.

REMEDY
1. Recharge or replace.
2. Repair or replace defective paits.

3. This can be due to extended idle or
storage periods, or to improper
preparation of the engine for storage, in
which case the parts may be rusted,
corroded orseized. Broken piston rings,
gears, etc., may also cause seizing.
Repair or replace defective parts.
4. This can be due to rain water entering
uncovered exhaust pipe, leaking
cylinder head gasket, cracked block or
cylinder head. Repair or replace
defective parts.
1. Specific gravity of batteries too low.
Charge batteries. Starter not delivering
maximum torque. Repair or replace
defective parts. Poor connection and/or
high cable resistance.
2. Check fuse, glow plugs, and wiring.
3. Check all engine controls for proper
adjustment and operation.
4. Check fuel systemdrain water separator,
and replace fuel filter.
5. Test and repair or replace nozzles.
6. Adjust valve clearance.

ENGINE
REMEDY

POSSIBLE CAUSES

TROUBLE

1. Batteries weak.
2. Insufficient fuel in fuel tank.

Engine hard to start

3. Incorrect grade of fuel.
4. Clogged filterlsediment bowl.

5. Injection nozzles not operating
properly.
6. Fuel transfer pump not operating
properly.
7. Air in fuel system.

1. Recharge or replace batteries.
2. Check fuel level in tank. Fill with
specified fuel if necessary.
3. Drain fuel system. Fill the tank with the
specified fuel.
4. Replace filter, clean sediment bowl,
when used.
5. Test and repair or replace nozzles.

6. Repair or replace fuel transfer pump.
Clean transfer pump filter.
7. Correct air leaks in low pressure side of
fuel system. Prime fuel system.
8. Insufficient air supply to cylinders. 8. Clean air cleaner and intake manifold.
9. Time fuel injection pump.
9. Fuel injection pump improperly
timed.
10. Adjust valve lash clearance.
0. Valve lash incorrect.
11. Replace affected parts. Perform
1. Piston rings or cylinders worn.
cylinder leak down test.
12.
Recondition or replace
12. Valves warped or pitted.
valves and/or guides.
1. Adjust low idle speed.
Engine stops frequently 1. Idling speed too low.
2. Check fuel system for blockage.
2. Restricted fuel supply.
3. Check fuel solenoid.
3. Fuel shut-off solenoid.
1. Fill fuel tank with specified fuel and
Engine stops suddenly 1. Out of fuel.
prime fuel system.
2. Check fuel system for blocked lines and
2. Restricted fuel supply or fuel
clogged filter.
return line.
3. Remove debris from radiator core.
3. Radiator air passages clogged.
4. Adjust fan belts to proper tension.
4. Fan belts loose.
5. Test the thermostat for proper
5. Thermostat inoperative.
operation.
6.
Check fuel solenoid, and other safety
6. Malfunctioning fuel solenoid,
shutdown switches.
or safety switch.
operation of engine oil
7. check for
7. Poor engine lubrication.
pump.
8. Repair or replace the water pump.
8. Water pump malfunctioning.
9. Perform cylinder leak down test.
9. Major engine failure.

ENGINE
TROUBLE
Engine shows loss of
power

POSSIBLE CAUSES
1. Insufficient supply of air to
cylinders. Restricted exhaust
system.
2. Insufficient supply of fuel to
injection nozzles. Water in
fuel system.
3. Governor not operating properly.
4. Air in fuel system.

5. Clogged fuel filter.
6. Improper valve lash.
7. Fuel injection pump improperly
timed.
8. Inoperative fuel injection pump
or injection nozzles.
9. Cylinder cutting out.

REMEDY
1. Clean air intake system. Clean exhaust
system.
2. Check fuel system. Drain water
separator.
3. Check engine operating speed.
4. Prime fuel system. Check for air leaks on
suction side of fuel transfer pump.
Check for air in return fuel.
5. Change filter.
6. Adjust valve lash clearance.
7. Time fuel injection pump.

8. Repair or replace affected parts.
9. Locate "missing" cylinder as follows:
Run engine at low idle speed and cut out
each fuel injection nozzle in turn by
loosening the fuel injection line nut
attaching line to fuel injection pump.
Cover fittings before
loosening. Fuel under
pressure can ponetmte the skin and can
cause blood poisoning or a serious skin
infection.
Adecrease in engine speed with line nut
loosened indicates nozzle for that
cylinder is functioning properly. If
engine speed does not decrease, nozzle
is malfunctioning and must be serviced.
10. This may be due to leaking valves or to
worn piston rings or cylinder bores. Use
a suitable leak down tester and check
each cylinder as detailed later in this
section.

10. Loss of compression.

IEngine runs unevenly
TROUBLE

and vibrates
excessively

smoke from exhaust

Engine emits bluishwhite smoke from
exhaust

REMEDY

POSSIBLE CAUSES
1. Idle speed.

1. Adjust idle speed.

2. Fuel supply erratic or insufficient
air intake.
3. Fuel injection pump malfunctions.
4. Valves in bad condition.
5. Plugged fuel filter.
6. Fuel injection nozzle malfunctions.
1. Air system clogged.
2. Incorrect injection pump timing.
3. Improper fuel.

2. Check fuel system and air intake.

4. Lack of good injection nozzle
spray pattern.
1. Engine operating temperature
too low.
2. Failed glow plugs(s).
3. Clogged injection nozzles.
4. Low compression.

5. Early fuel injection pump
timing.
1. Fuel pump improperly timed.

3.
4.
5.
6.
1.
2.
3.

Check fuel injection pump.
Recondition valves and seats.
Replace filter.
Repair nozzle.
Check enaine air intake system.
Check f u i injection pump timing.
Drain fuel system and refill with specified fuel.
4. Clean and adjust nozzles.
1. Check thermostat operation.

2. Check continuity.
3. Clean and adjust nozzles.
4. Make cylinder leakdown test and necessary repairs.
5. Check and adjust timing.
1. Check and adjust.

knocks

2. Loose bearings.
3. Loose piston.
4. Loose flywheel.

5. Improperly adjusted valve(s).
6. Foreign material in cylinder(s).

2. Replace bearings.
3. Inspect piston assembly. Replace parts
required.
4. Check tightness of flywheel bolts.
Tighten or replace parts required.
5. Check and adjust valve lash clearance.
6. Make necessary repairs.

CYLINDER LEAK DOWN
TEST PROCEDURE
(Using Onan Cylinder Leakage
Tester No. 420-0343)

The Cylinder Leakage Tester is used to determine the
location and relative amounts of compression losses
in an engine. This test can locate leaks at the intake
and exhaust valves, head gaskets, and excessive
leakage past the rings.

Cylinder Leakage Test
With engine at normal operating temperature air
pressure is applied when the piston is at TDC of the
compression stroke. At this time both valves are
closed and except for a small amount of air leaking
past the piston ring end gap no air should escape
from a good cylinder. Check each cylinder for leakage as follows:

1. Before connecting air to the inlet fitting, turn the

1. Set-up Cylinder Leakage Tester and calibrate.
2. Connect the remote start switch to the start
solenoid.
3. Clean area around injection nozzles and remove
all nozzles.
4. Remove air cleaner, oil fill cap, and radiator cap.
5. Install Tester in same manner the fuel injection
nozzle was installed. Make certain the cylinder
being tested is at TDC of the compression stroke.
6. Connect test to adapter. Watch the engine crankshaft. If it turns stop the test. Remove the tester
and reposition piston at TDC.
7. Listen for air leakage at exhaust pipe, intake
manifold, and from crankcase.
8. Check gauge and record reading. A leakage reading of less than 20°h and no "air leaking" heard in
exhaust pipe, air intake, or crankcase indicates a
good cylinder.
A leakage reading greater than 20% on a properly
broken-in engine or "air leaking" heard at
exhaust pipe, air intake, or crankcase indicates a
need for service.

CLT regulator to the left a couple of turns.
2. Connect air to inlet fitting and turn CLTregulator
to the right in small steps until the gauge reads
zero.
3. Momentarily depress the valve in the connection
end of the outlet to engine hose. The needle
should rise, then return to zero.
4. If needle does not return to zero repeat Steps 1.2,
and 3. When the Cylinder Leakage Tester reads
zero it is properly calibrated and ready to use.

A. Air escaping at air intake indicates a leak at the
intake valve.
8. Air escaping at exhaust pipe indicates a leak at
the exhaust valve.
C. Air escaping at radiator filler cap indicates a
blown head gasket or a crack in the water
jacket.
D. Air leaking into crankcase indicates worn or
broken rings or scored cylinder walls.

In order to obtain an accurate test, make certain the
cylinder leakdown tester has been properly tested
and calibrated. Do not rebuild an engine because of
high cylinder leakage readings obtained with a leakdown tester unless the unit is known to be accurate.

Regulator Calibration
The Cylinder Leakage Tester (CLT) requires an outside source of air pressure [483 to 1380kPa (70to 200
psi)] to be connected to the air inlet fitting.

ELECTRICAL SYSTEM
TROUBLE

POSSIBLE CAUSES

Alternator not charging 1. Alternator drive belt loose or
broken.
2. Alternator regulator inoperative.
3. Alternator inoperative.
Alternator output low
and/or unsteady

Batteries will not
hold charge

Starter will not crank
engine.

1. Alternator drive belt improperly

adjusted.
2. Brushes sticking in brush holders.
3. Brush spring tension too low.
4. Slip ring dirty or worn.

5. Voltage regulator operating
improperly.
1. Loose terminals or
connections.
2. Short in electrical system.
3. Short circuit or bad
cell in battery.
4. Electrolyte level low
(alternator output excessive
or cracked battery case.)
5. Voltage regulator inoperative.
1. Batteries weak.
2. Cables and/or connections
loose or corroded.
3. Starter switch inoperative.
4. Starter brushes worn or not
contacting properly.
5. Starter brush springs weak.
6. Starter commutator dirty
or worn.

Starter pinion will
not engage with
flywheel ring gear

7. Starter armature shaft
bearings worn (armature
drags on fields).
8. Starter armature burned out.
1. Broken or excessively
worn parts.
2. Defective solenoid.
3. Worn overrunning clutch.

REMEDY
1. Adjust or replace drive belt.
2. Remove regulator and replace.
3. Remove alternator for repairs or
replacement.
1. Adjust drive belt.
2. Free brushes in holders.
3. Replace brush springs.
4. Clean slip ring or remove alternator
for repair or replacement.
5. Remove regulator and replace.
1. Tighten affected parts.

2. Correct short.
3. Remove and replace battery.
4. Reduce charging rate. Remove and
replace battery or add water.

5. Remove regulator and replace.
1. Check batteries.
2. Tighten all loose connections
and clean corrosion from all terminals.
3. Replace switch.
4. Install new brushes.
5. Check brush spring tension, replace
springs if necessary.
6. Clean commutator, machine
commutator and undercut mica if
necessary.
7. Replace worn bearings and
related items.
8. Replace armature.
1. Replace broken or worn parts.

2. Replace solenoid.
3. Replace clutch.

FUEL SYSTEM

TROUBLE
lnsuffic~entfuel
supply to injection
nozzles

1. No fuel in fuel tank.

Air in fuel system

Insufficient air supply
to cylinders

Rapid wear on engine
parts

1. Fill fuel tank with specified fuel.

Prime fuel system.
2. Inoperative or plugged fuel
transfer pump.
3. Injection nozzle valve
sticking in valve body.
4. Fuel lines/fuel filter/clogged.

REMEDY

POSSIBLE CAUSES

5. Fuel injection pump
malfunctioning.
6. Injection nozzles improperly
adjusted.
1. Loose fuel line fitting or leak
in fuel line on suction side
of fuel transfer pump.
2. Damaged fuel filter.
1. Air cleaner clogged.
2. Excessive dirt buildup
in turbocharger.
3. Leaks in engine intake and/or
exhaust manifolds reducing
turbocharger efficiency.
4. Turbocharger rotating assembly
bearing seized.
1. Dirt admitted with
intake air.

2. Dirty crankcase oil.

3. Improper fuel.

4. Valves hitting pistons.

2. Repair or replace transfer pump.
Clean inlet filter.
3. Replace seal and valve
assembly in nozzle holder body.
4. Clean fuel system components,
replace fuel filter.
5. Remove fuel injection pump for
service.
6. Adjust injection nozzles.
1. Tighten loose fitting or replace

damaged line.

2. Replace fuel filter.
1. Replace air filter element.

2. Thoroughly clean turbocharger.
3. Tighten loose manifold retaining
nuts or capscrews. Replace manifold
gaskets.
4. Overhaul turbocharger.
1. Inspect air cleaner body, pipe,
connecting hoses, gaskets, etc.,
thoroughly for cracks or openings
which would allow air to enter engine
without passing through air cleaner.
Make necessary repairs.
2. Change engine oil and the oil filter
element at the intervals
recommended. Keep oil clean when
filling engine.
3. Use the proper fuel. It is important that
the fuel be within the specified limits
for ash, carbon, sulphur. etc., to prevent excessive wear on engine parts.
4. Check valve recession in head.

COOLING SYSTEM
TROUBLE
Engine operating
temperature too high
with ample coolant
in system

Engine operating
temperature too high
due to loss of coolant

Engine operating
temperature too low

POSSIBLE CAUSES

REMEDY

1. Temperature gauge inoperative.

1. Check gauge. Replace if necessary.

2. Radiator air passages
restricted.
3. Thermostat inoperative.
4. Loose or broken fan belts.
5. Lime deposits in water
passages of radiator,
cylinder head and/or
cylinder block.
6. Water pump inoperative.
7. Engine pulling excessive load.
8. Engine speed set too high.

2. Clean exterior of
radiator.
3. Replace thermostat.
4. Adjust or replace fan belts.
5. Thoroughly clean affected areas.

1. External leaks.

2. Ruptured oil cooler core
(oil in coolant).
3. Engine cylinder head
gasket leaking.
4. Engine cylinder head cracked.
5. Engine cylinder block cracked.
1. Thermostat stuck in open
position.
2. Operating in extremely
cold weather.

6. Replace water pump.
7. Reduce load.
8. Adjust speed to within
specified rpm limits.
1. Repair affected parts.

2. Replace oil cooler core.
3. Replace gasket and torque
cylinder head bolts as specified.
4. Replace cylinder head.
5. Replace cylinder block.
1. Replace thermostat.
2. Provide covers for radiator
and engine side openings.

OIL SYSTEM
POSSIBLE CAUSES
No oil pressure

1. lnsufficient 011in crankcase.
2. Oil pressure gauge inoperative.
3. Oil pickup cracked or clogged.
4. Oil pump inoperative.

Low oil pressure with
proper oil level in
crankcase

5. Regulating valve stuck open.
1. Oil pressure gauge inaccurate.

1. Fill crankcase to proper level.
2. Replace gauge.
3. Remove and clean the screen or
replace pickup assembly.
4. Repair or replace oil pump.
5. Remove and clean.
1. Check gauge. Replace if necessary.

2. lmproper crankcase oil or
diluted with fuel.
3. Oil pressure relief valve or
regulator valve stuck in open
position.
4. Main and/or connecting
rod bearings worn.
5. Camshaft bearings worn.
6. Oil pump worn.
1. Oil pressure gauge inaccurate.
2. Oil pressure regulating valve
sticking.
3. lmproper crankcase oil.
1. lnsufficient oil in crankcase.

2. Fill crankcase with specified crankcase
oil.
3. Clean, repair, or replace
affected parts.

2. Engine oil cooler clogged.
1. External oil leakage
(gaskets, etc.).
2. Engine oil seals worn or
damaged.
3. Crankcase oil diluted
with fuel.
1. Pistons, rings, and/or
cylinder bores worn.
3. Rings stuck in piston
ring grooves.
6. Valve guides and seals worn.

2. Clean or replace the oil cooler.
1. Correct all external leaks.

k
Excessive oil pressure

REMEDY

4. Replace bearings.

5. Replace bearings.
6. Repair or replace oil pump.
1. Check gauge. Replace if necessary.
2. Clean, repair, or replace regulating
valve.
3. Fill crankcase with specified oil.
1. Fill crankcase to proper level.

lubricating oil

consumption

Excessive oil
consumption during
first 250 hours
of operation and no
indication of
improvement

Rapid wear on engine
parts

7. Plugged breather.
1. Rings not seated properly.

2. Pistons or cylinders
scored.
1. Crankcase oil contaminated.
2. lmproper engine lubricating
oil beina used.

2. Replace oil seals.

3. Fill crankcase with specified oil.
4. Replace or repair affected parts.

5. Clean ring grooves and
replace rings.
6. Replace valve guides. Check related
parts.
7. Clean breather.
1. Allow more time for break-in.
Make certain specified
crankcase oil is used
and engine is at operating
temperature.

2. Check cylinder leakage.

GI system with clean
engine oil. Replace engine
oil filter.
2. Fill system with crankcase oil
of proper specifications.
1.

TURBOCHARGER
When operating, each turbocharged engine has its
own distinctive sound or noise level. In many instances, malfunctions can be detected when the
noise level changes. A change in noise level to a
high-pitched screech indicates an air leak between
air cleaner and engine or an exhaust gas leak in the
exhaust system, between turbocharger and exhaust
manifold. Noise level cycling from one level to another
is an indication of a plugged air cleaner, a restriction
in air intake piping, heavy build up of foreign matter in
compressor, or operation at altitudes above 3048 m
(10,000ft). A sudden reduction in noise level and
power loss that results in black or blue smoke and
excessiveoil leakage indicatesa turbocharger failure.

A turbocharger cannot correct or overcome engine
malfunctions or deficiencies in the fuel and air intake
system. If a turbocharged engine has malfunctioned
and turbocharger has been inspected and is in good
operating condition, proceed with troubleshooting
as though engine were not turbocharged.
Simply replacing a good turbocharger with another
will not correct engine malfunctions. Too often turbochargers are removed from engines before the cause
of a malfunction has been determined. Always inspect
and assess turbocharger condition before removal
from engine.
Usethe troubleshooting list that follows in diagnosing
and correcting unsatisfactoryturbocharger operation
and related engine operation.

TURBOCHARGER
<

POSSIBLE CAUSES

TROUBLE
Noisy operation

Loss of engine power.
excess smoke

REMEDY

1. Restricted air intake piping or air
cleaner.
2. Leak in air intake piping or exhaust
system.
3. Damaged bearing or other
components causing compressor
impeller or turbine wheel to rub
against housing.

1. Remove restrictions and clean or
replace air cleaner.
2. Tighten all connections and replace
gaskets as required.
3. Remove turbocharger for
replacement or repair.

1. Leak in air intake piping or exhaust
manifold.
2. Restricted air intake piping or dirty
air cleaner.
3. Foreign matter lodged in
compressor impeller or turbine
wheel. Damaged impeller or
turbine wheel.
4. Excessive build up of foreign
matter in compressor.
5. Oil leakage from seals.
6. Back pressure on turbo exhaust
too high.
7. Interference or binding in rotating
assembly. Bearing seizure.
8. Insufficient fuel supply to engine.

1. Tighten loose connections or

replace exhaust manifold gaskets.
2. Remove restrictions and clean or
replace air cleaner.
3. Clean or replace turbocharger if
damaged. Determine source of
debris.
4. Thoroughly clean compressor
assembly. Clean or replace air
cleaner and check for leaks.
5. Remove turbocharger for
replacement or repair.
6. Correct restriction in exhaust
system.
7. Remove turbocharger for
replacement or repair.
8. Replace fuel filter and inspect fuel
system.

Oil in intake manifold
or exhaust pipe

1. Seal failure.
2. Restriction in air cleaner or air
intake creating suction.

1. Replace or repair turbocharger.
2. Remove the restriction.

Vibration and noise

1. Damaged impeller or turbine
blades. Worn or damaged bearing.
2. Restricted air intake system.

1. Replace or repair turbocharger.
2. Inspect and clean air cleaner and
air intake piping.

PAGE

SU~JECT

............................................... 6-1
.................................................... 6-1
................................. 6-1
........................................6-1
...........................................6-1
..............................................6-2
..............................................6-2
...................................... 6-2
......................................... 6-2
.................................... 6-4
..................................... 6-4
...................................... 6-4
........................................... 6-4
.................................................. 6-5
............................................... 6-5
...................... 6.5
................................................6-5
.................................................6-5
............................................ 6-5

E~~l~ESET-UP
~~tteries
Crankcase Oil Recommendations
Fuel commendations
FuelTankandLineS
coolingsystem
Exhaustsystem
p
~
~ INSTRUCTIONS
.
~
~
~
~
T
F~~~ SYSTEMPRIMING
p ~ ~ . ~ ~ AND
~ T STARTING
I N G
Twenty Second Glow Plugs
Seven Second Glow Plugs
ENGINE SHUTDOWN
OPERATION
ApplyingLoad
Exercise of Engine on Generator Set Application
DustandDirt
HighAltitude
High Temperatures
LOW Temperatures
Out-Of Service Protection
Returning Unit to Service

............................................ 6-5
....................................... 6.6
....................................... 6-6

ENGINE SET-UP
inspect the engine visually. Check for loose or missing
parts and any damage that may have occurred in
shipment.

~ c ~ " i TOil,~fuel,
o and
~

coolant have been
drained from the engine prior to
shipping from Onan. Severe damage will result if
engine is started without oil.
Batteries
The batteries and battery cables used for starting the
engine should be of sufficient size to provide prompt
starting. Undersized batteries will result in poor starter
operation and a very short starter service life.

1-r

Explosive gases are emitted from
batteries while charging. Ignition of
these gases can result in an explosion and severe
personal injury. Do not smoke or allow any spark
producing device near batteries while servicing.

Crankcase Oil Recommendations
Fill crankcase with correct amount of oil. Refer to
SPECIFICATIONS section for crankcase capacity.
When adding oil between oil changes, it is preferable to
use the same brand, as various brands of oil may not be
compatible together. Refer to SECTION 7, MAINTENANCEfor recommended oil change procedures.
Do not overfill crankcase. Excess oil
causes foaming and can cause loss
of lubrication and higher operating temperatures,
resulting in engine damage.
Recommended L engine oil specifications are 15W-40,
30W, 20W-20.1OW oil meetingthe American Petroleum
Institute (API) classification CD/SF, CD/SE, or Military
Specification MIL-L-2104C. When a SW-20 or SW-30 oil
is required, it must be a synthetic oil meeting Military
Specification MIL-L-46167. MIL-L-2104C. or MILL-461528.

Fuel Recommendations
Fill the fuel tank with a good quality fuel obtained from a
reputable supplier. The quality of fuel used IS important
in obtaining dependable performance and satisfactory
engine life. Fuels must be clean, completely distilled,
well refined, and non-corrosive to fuel system parts.

Due to the precise tolerances of diesel injection systems, it is extremely
important the fuel be kept clean and free of water. Dirt
or water in the system can cause severe damage to
both the injection pump and the injection nozzles.
Fuel vapors create fire and explosion
hazards which can result in severe
personal injury or death. Do not add gasoline, gasohol,
or alcohol to diesel fuel. Do not permit any flame,
cigarette, or other igniter near the fuel system.
Use ASTM2-D (No. 2 Diesel), ASTM1-D (No. 1 Diesel)
fuel with a minimum Cetane number of 40*. Number 2
diesel fuel gives the best economy and performance
-under most operating conditons. ~t temperatures below
0°C (32"F), Number 2-0 fuel may pose operating
problems. At colder temperatures, use Number 1-D fuel
(if available) or use a "winterized" Number 2-0 (a blend
of Number 1-D and Number 2-0). The blended fuel is
normally called Number 2-0 also, but can be used in
colder temperaturesthan non "winterized" Number 2-0
fuel.
Do not add gasoline, gasohol, or
alcohol to diesel fuel. Damage to fuel
injection system or engine may result.
*NOTE: Fuels with Cotam numbersh i g h than 40 may be needed in
higher aHitudr or whon exbumdy low ambient temperatures a n
encountwed to prevent midires and resultant excessive smoke.

Use low sulfur content fuel having a cloud point of at
least 10degrees below the lowest expectedfuel temperature. Cloud point is the temperature at which wax
crystals begin to form in diesel fuel.

SpiIIed fuel can ignite and cause
serious personal injury or death.
Nww #/ th.iue/ iank when the engine is running.
Fuel leaks create fire and explosion
hazards which can resun in severe
persondinjury or death. Always usea length of flexible
tcsWngbeiwe8nengineand the fuelsupply line to avoid
tinotailurn and leaks due k vibrstion. The fuel system
must med applicable codes.

Fud T'@and Ucrss
When more than one engine share the same fuel tank,
do not connect to an existing fuel line at a point above
the fuel supply level. Install a fuel shut-off valve in the
tank for service convenience.
:

-20

Tmmraw,.

You E s W I 8.(m N u t OtI C M p .

Ls.(OP

SW-20 and 5W-30 minerat base oils are not recom..
mended-* wij$w&%r)wm
any ccmMm.

T h m g i n e requires a fuel supply line wtth a separate
return line. Both lines should be connected to standpipes in Redank wtth the opening for each 2" minimum
from the W m of the tank to allow space for water and
sedimenk to settfeand 6 elimihate siq&q$$g~rc+blems.

Exhaust System

Installthe fuel supply line from tank to the inlet in the fuel
pump. Connect fuel return line to tee fitting at injection
pump. Use approved flexiblefuel lines or connections at
the engine to absorb vibration.

The exhaust system must efficiently expel all engine
combustion products and muffle exhaust noises with
minimum back pressure. If back pressure is too high, the
volumetric efficiency of the engine is reduced, fuel
economy drops, exhaust temperature increases, and
valve life is shortened.

Do not use dissimilar metal lines,
fittings, and fuel tanks in the fuel
Hazardous fuel leaks may be caused by
electrolytic corrosion. An explosion or fire can cause
severe personal injury or death.

I - isystem.

Exhaust products of any internal combustion engine are
toxic and can cause injury, or death if inhaled. All engine
applications, especially those within a confined area.
should be equipped with an exhaust system to discharge
gases to the outside atmosphere.
On service calls, always inspect
/
exhaust systems for possible leaks.
Report any exhaust hazards to the owner/operator and

Coolant System
Verify that all drain cocks are closed and all hose
clamps secure. Onan recommends the use of clean
ethylene glycol anti-freeze solutions in closed cooling
systems during normal operation and storage periods.
Be sure anti-freeze solution will protect the cooling
system during the coldest winter weather. Use only a
reliable brand of ethylene glycol (permanent type) antifreeze which contains a rust inhibitor but does not
contain a stop-leak additive.

warn them of the potential dangers to life i f not
repaired.

PRE-START INSTRUCTIONS
Preparations for the initial start up and each additional
start up thereafter should include careful checks of the
following:
1. Check all componentsfor mechanical security. If an

Coolant fill rate must not exceed 11.4
:*-ON
liln.(3.0 gallons) per minute. Filling
too fast may result in incompleteengine coolant filling
and possible engine damage at start-up.

abnormal condition or defective part is detected.
repair or service as required. The engine should be
kept free of dust, dirt, and spilled oil or fuel.

2. Check engine crankcase oil level.

Use a minimum 50-50 mix of ethyleneglycolanti-freeze
and soft water to fill the cooling system. Use soft water
whenever available. Well water often contains lime and
other minerals which eventually may clog the radiator
core and reduce the cooling efficiency. Check cooling
system for leaks after anti-freeze solution has been
added.

3. Check radiator coolant level.
4. Check fuel supply level.

5. Inspect the air cleaner; service if necessary.

6. lnspect exhaust system for possible leakage and
cracks.

Fill cooling system with appropriate mixture of antifreeze. To assure complete filling of the cooling system
the cylinder head and block should
bled to prevent
air lock. This can bedone by looseningoneof the plugs
or senders located in the water pump before filling.
When coolant appears, retorqueplug to T7 Nm (150 inIb) and finish filling. An additional pocket of air will
remain in the cylinder headStart engineandoperatefor
approximately 10 minutes or untilm o s t a t opens. As
coolant circulates, air trapped in the cylinder head will
be released.

FUEL SYSTEM PRIMING
The fuel system must be primedprior to initial start up or
after engine has run out of fuel.

Due to fho
I
s i
dh.,tuclk
dean
h m of

td.rsnces of diesystem,,
i s ext-y
imporbnt
k@
and
waier. Dirt
ormt.rinfho~cur~~18esewred8msgoto
both fho injection pukp and the injection nozzles.
-88

Fill with additional coolant as r w . Coolant lwel
should be maintained ata level midway betuueen top of
radiator core and fMer neck. if vehicte is equipped with a
coolant recovery tank. coolant lever in recovery tank
must be between cold and hot marks.

1. Priming (transfer pump, fuel filter, and injection
pump housing).low pressure fuel system.

A. Chedc fuel level in fuel tank. Open fuel shut off
valve if one is present
t'irtgni'.

8. Loosenthehretfi{$erto@jection pump line at the
,ir- *7:
:Y?~Ir

2. Priming High Pressure Fuel System.
INJECTOR

This part of the system is usually self-priming since
any trapped air in the injection pump is usually
forced out through the injection nozzle. If, however,
engine has run out of fuel, been shut down for an
extended period, or has had fuel injection lines
removed, it may be necessary to prime as follows:

A. Loosen fuel injection line connecting nut (Figure 1) attaching each line to corresponding
nozzle holder.

8. Place speed control in high speed position and
stop control in RUN position.
C. Energize starting motor. (Do not operate starting
motor for more than 30 seconds at a time
without pausing two minutes to permit starter to
cool.)

1AWARNING 1

Fuel penetration of the skin
can cause severe personal
injury. Do not let the n o u k high-pressure
fud spray against skin surf8ces.

FIGURE 1. INJECTION PUMP AND NOZZLE

C. Actuate the priming lever (Figure 2) on the
side of the transfer pump until fuel flowsfrom
the fitting.
Ifreslstantr Is not felt whon opomtlng priming hver the
camshaft transfer pump l o b is up. Turn engine one
revolution to permit hand priming.

D. Tighten fuel line at the injection pump inlet.

FIGURE 2.

FUEL TRANSFER PUMP

D. When fuel flows from the end of high pressure
fuel injection lines, stop starting motor and
torque connection nuts.

PREHEATING AND STARTING

6. If engine fails to start after 30 seconds, wait two
mirstes before recranking, and repeat steps 3 and 4
abo.,e. Absence of bluelwhite exhaust smoke
during cranking indicates no fuel being delivered. If
engine does not start on first attempt, check fuel
supply system.

The engine starting procedure depends on the controls
and safety shutdown equipment furnished by Onan or
the original equipment manufacturer.
When controls are furnished by the original equipment
manufacturer (OEM), follow their instructions for stopping, starting, and operating the engine and their
equipment.
The following instructions supplement OEM starting
instructions and should be followed when controls are
furnished by Onan. To aid in starting of all indirect
injection L-SeriesDieselengines, preheating is required
at temperatures below 21 OC (70°F).

7. Allow engine to warm up before applying load.
Seven Second Glow Plugs
1. Place transmission in park or neutral position.
2. Turn key switch to engine run position.
3. Wait until glow plug preheat light goes out before
cranking engine.

Do not engage starter for periods
longer than 30 seconds without
allowing 2 minutes tor starter to cool.

4. Turn key switch to start position to engage starter.

On engines equipped with manual cold start advance pull cold start advance knob out at temperatures below O°C (32'F). Push knob in after engine
starts and runs for approximately two minutes.

Use of ether as a starting aid can
cause an explosion resulting in
severe personal injury. Heat of compression or hot
glow plugs can cause a sudden ignition of the ether
vapor. Do not use ether as a starting aid.

5. If engine fails to start after 30 seconds, wait two
minutes before recranking, and repeat steps 3 and 4
above. Absence of blue/white exhaust smoke
during cranking indicates no fuel being delivered. If
engine does not start on first attempt, check fuel
supply system.

Use of ether as a starting aid can
causean explosionmsultingin engine
damage. Heat of compression or hot glow plugs can
cause ignition ot the ether vapor. Do not use ether as a
starting aid.
Twenty Second Glow Plugs
1. Disconnect load from the engine.

2. Energize fuel solenoid or place all controls in
START/ RUN position.
3. On engines equipped with a glow plug preheat
indicator light, preheat until light goes out indicating
engine is ready for starting.
4. On engines equipped with twenty second glow
plugs and no preheat lamp energize preheat circuit
for specified period of time, determined by ambient
temperature.

6. Allow engine to warm up before applying load.
Within seconds after starting engine, oil pressureshould
exceed 60 kPa (10 psi) minimum. After engine has
reached operating temperature, oil pressure should be
in the range of 207 to 380 kPa (30 to 55 psi) at full load
rpm.

Overvoltagewill immediately destroy

the glow plugs. Do not apply overto the sbrting c i m H at any ffmo. If it becomes
nec&sary to use m aWtlonal source otpower to start
the engine, use a &thry of equal voltageconnectedin
padW.

ENGINE SHUTDOWN

Ambient T m p m t w r
PnhratTkm
Above21°C(700F)
10-20seconds
-18°Ct~210C(O-700F).................... 25-35secOnds
Below -18°C (0"F) ........................ 30-45 seconds

1. De-energize fuel solenoid or turn STARTISTOP
switch to stop position.

Limit preheating to recommended
periods; longer periods a n in the

2. If stop circuit fails, close manual fuel valve. This
manual-valve is optional.

........................

heater element.
5. Continue to preheat while energizing the start
circuit De-energize preheat and start circuits when
engine will run without the aid of the starter motor.

Always allow engine to run at idle
without I d for at least 2 minutes
ktom s w n g . mis allows engine to cod gradually
and rnlfomly.

OPERATION
Operation, following prestart, preheat and starting,
involves several checking and servicing procedures
that will help the owner-operator extend the engine's
life.

Dust and Dirt
1. Keep engine clean.
2. Service air cleaner prior to each start-up.
3. Change crankcase oil every 100 operating hours.
4. Keep oil and fuel in dust-tight containers.
5. Keep throttle linkage clean.

Applying Load
If practical, allow the engine to warm up before
connecting a load. Continuous engine overloading
causes higher operating temperatures that can
damage the engine. The exhaust system may become
- fouled by combustion deposits during periods of
operation at light loads.

Exercise of Engine on
Generator Set Application
A diesel engine on stand-by service that is relied
upon to perform under critical conditions, should be
exercised at least every 30 days.

Exercise period should be of sufficient duration to
allow engine to reach normal operating temperature
while carrying at least 50% of normal load.
When the engine is used under conditions of extreme
temperatures, humidity, dust, sand, etc., it may be
necessary to accelerate maintenance intervals and
exercise periods to as often as weekly.
To exercise engine:
1. Before starting, check lubricating oil and coolant
levels. Make complete visual check of unit.
2. Start engine and run 15 minutes with speed
control at half position.

3. Run engine at rated speed with whatever load is
available, up to full load, for the-time needed to
obtain two consecutive water temperature readings of 71°C (190°F) minimum at 15 minutes.
Check and correct.any coolant or oil leaks.

Contact wlth hot coohnt might
lbPWaRNl
N
G
1u,t,8wbw,,,,t
i d hot, pre88urit.d coolant from a c i d
cooling ryrtem.
4. Run engine at half speed with no load for 5
minutes to allow engine to cool evenly.
5. Stop engine.
If accumulated hours of operation during exercise
periods do not total 200 hours within a 6 month
period, the oil filter and lubricating oil should be
changed regardless of hours. If in a 12 month period
engine hours do not total 400, replace the fuel filter.

High Altitude and High Temperatures
Maximum power will be reduced approximately 3
percent for each 304.8 m (1000 ft.) above 90 m
(295 ft.) on naturally aspirated engines, and above
1525 m (5000 ft.) on turbocharged engines.
Maximum power will be reduced approximately 1.8%
per 10°C (1% per 10" F) above 25OC (77°F).
See that nothing obstructs air flow to and from the
engine. Keep cooling system filled to proper level
with coolant. Be sure that thermostat and pressure
cap function properly. Keep cooling system clean.
If permanent application is expected to exceed
1000 m (3280 ft.) on naturally aspirated engines,
1525 m (5000 ft.) on turbo engines or, if normal air
inlet temperature exceeds 40° C (105°F) or if a total
power reduction due to both pressure and temperature exceeds 1O0/0, an injection pump change is
recommended to reduce the fuel flow rate.

Low Temperatures
Diesel fuels are sensitive to changes in ambient
temperature. All diesel fuels have a certain amount of
heavy paraffin-like (wax) components, which are
high in energy value and help improve fuel economy.
When fuel temperatures fall to less than about -7°C
(20°F), the heavy paraffin components begin to
solidify into wax flakes. If fuel temperatures become
low enough, the flakes can build up in the fuel filters
and prevent fuel from reaching the engine.
Number 2-0 fuel hasa higher level of heavy components
and is more subject to waxing than Number 1-0 (or a
"winterized" 2-0) fuel. When operating at temperatures
below 0°C (32OF), use Number 1-D, or Number 2-0 that
has been blended with Number 1-0 for winter use.

To improve c ~ l weather
d
starting and operat~on,use of
an engine block heater is recommended. A fuel heater
properly insWed helps prevent wax from plugging the
fuel filter.
1. Usehcorrectv f d t y oil for temperatureconditions.
Change oil only when engine is warm. If an unexpectedtemperaturedrop requiresan emergency oil
change, move the engine to a warm location or
apply heatedair (never useopen flame) externally to
the oil pan until oil flows freely.

2. Use fresh fuel. Protect against moisture condensation. Keep fuel tanks full. Temperature of fuel
delivered to engine filter must be above its cloud
point to prevent filter blockage.

Use of ether as a starting aid can
cause an expIosion resulting in
severe personal injury. Heat of compression or hot
glow plugs can cause a sudden ignition of the ether
vapor. Do not use ether as a starting aid.
Use of ether as a starting aid can
cause an explosion resulting in
engine damage. Heat of compression or hot glow
plugs can cause an ignition of the ether vapor. Do
not use ether as a starting aid.
3. Keep fuel system clean, and batteries in a well
charged condition.

Overvoltage will immediately
destroy glow plugs. Do not apply
overvoltage to the starting circuit at any time. If it
6ecomes necessary to use an additional source of
power to start the engine, use a suitable battery of
equal voltage connected inparallel.

Out-Of-Service Protection
The inherent lubricating qualities of No. 2 diesel fuel
should protect the cylinders of a diesel engine for at
least 30 days when the unit is not in service. To protect
an engine that will be out of service for more than 30
days, proceed as follows:

2. Shut down engineand drain crankcase oil while still
warm. Refill and attach a warning tag indicating
viscosity of oil used.
3. Remove glow plugs and pump 28 grams (1 ounce)
of rust inhibitor (or SAE #10 oil) into each cylinder.
Use starter to turn engine over three to four
revolutions. This will evenly distribute the rust
inhibitor in the cylinders. Install glow plugs.
4. Service air cleaner per OEM specifications.
5. Clean throttle linkage and protect with a light coat of
oil.
6. Plug exhaust outlet to prevent entrance of moisture,
bugs, dirt, etc.
7. Clean and wipe entire unit. Coat parts susceptible to
to rust with a light coat of grease or oil.
8. Disconnect battery and follow standard battery
storage procedure.

Returning Unit to Service
1. Removecover and all protectivewrapping. Remove
plug from exhaust outlet.
2. Check tag on oil dipstick and verify that oil viscosity
is still correct for existing ambient temperatures.
Check oil level.
3. Clean and check battery. See SECTION 7.
MAlNTENANCEfor instructions.
4. Check that glow plugs are secure, correctly torqued,
and electrical leads connected.
5. Connect battery (ground terminal last).
6. Prime fuel system.
7. Refer to starting instructions for start-up.

1. Exercise the engine as outlined in EXERClSE OF

ENGINE ON GENERATOR SET APPLlCATlON
section.

After engine has started, excessive blue smoke is
exhausted until the rust inhibitor has burned away.

EXHAUST GAS IS DEADLY!
Exhaust gases contain carbon monoxide, a pdsonous gas that a n cause
u n c o n s c b w m s and death. It h an odorless and coWess gas formed during
combustion of hydrocarbon fuels. Symptoms of carbon monoxide poisoning are:

W*ss
Headache
4W&mssand Sbpiness

v m n g
Mtltcukr Twitching
Throbbing in Temples

H you expedence any of these symptoms, get out into tmsh air irnnmdiahly~shut
down the unit and do not use until it has bmh in8pedd.
ThebestprotscBionagainst carbonmonoxideinhalation isproper installationand
regular, frqient hpections d the con#@& exftw8i syrlwR. H you notice a
change ifi fhe swnd or apps.rance of exhaust system* shut the unit down
immediately and have it inspoctedand repahodat onceby[, com&nt
mechanic.
-.

7 Maintenance
SUBJECT

PAGE

........................................... 7-1
................................................ 7-1
..................................................7-1
........................................... 7-1
............................................. 7-1
................................................... 7-2
................................................... 7-2

ENGINE INSPECTION
DAILY CHECKS
OILCHANGE
OIL FILTER CHANGE
COOLING SYSTEM
Cleaning
BAmERlES
Cleaning
Checking Specific Gravity
Checking Electrolyte Level
Storage
FANBELT
FUELSYSTEM
FuelFilter
Fuel Injection Pump
CRANKCASE BREATHER
VALVECLEARANCE
PERIODIC MAINTENANCE SCHEDULE
AIRCLEANER
TURBOCHARGER

...................................................7-2
....................................... 7-2
...................................... 7-2
....................................................7-2
....................................................7-3
................................................ 7-3
...................................................7-3
........................................... 7-3
........................................ 7-4
............................................7-4
.............................. 7-4
.................................................7-4
.............................................. 7-4

ENGINE INSPECTION
Accidental starting of the engine or

PWARN~NG~electrica~arcing can cause severe

personal injury or death. Disconnect the battery cable
when repairs are made to the engine, controls, or
associated equipment.
Onan doer not recommend washlng
the dlerel englne. However, It you
muat warh the englne, do so only when the englne b
cold. Never wash a warm, hot, or runnlng englne.
Spnylng water or cleanlng solutlonr on a warm
englne or lnjectlonpump can cause terlous damage
to the englne fuel ryrtem.

After starting the operator should make a complete
visual and audible inspection of the engine. lnspect
exhaust system for possible leakage and cracks.
Locate leaks in muffler and piping while the engine is
operating. Repair all leaks immediately after they are
detected for personnel safety.

DAILY CHECKS
Check the following before starting the engine for the
first time each day:
1. Check all fuel lines and fittings for possible
leakage.
2. lnspect cooling system for possible leaks. Coolant level should be maintained at a level midway
between top of radiator core and filler neck. If in a
vehicle equipped with a coolant recovery tank,
coolant level in recovery tank must be between
cold and hot marks. Maintain coolant at a
concentration that will prevent freezing and
system corrosion.
3. Drain moisturefrom condensation traps and fuelwater separator (if so equipped).
4. lnspect intake system for leaks. Makecertain that
all clamps and fittings are tight and free of
potential leaks.
5. Check crankcase oil levelwith theengine off. If oil
level is at or below " a d d mark on dipstick
(Figure 1), add sufficient oil of the proper viscosity
as specified in SECTION 6, START-UP to bring
oil level to the full mark on the dipstick. Do not
operate engine with oil level below the "add"
mark.

CAUTION: 00 NOT
OVERFILL

FULL

- ADD
I

FIGURE 1. CRANKCASE DIPSTICK

To drain oil, place a pan under the drain outlet, and
remove the oil drain plug. After the oil is completely
drained, replacethe drain plug. Spin off oil filter element
and discard it Thoroughly clean filter mountingsurface.
Make sure new gasket is insertedin the element. Apply a
thin film of clean oil to the gasket Spin element down by
hand until gasket just touches mounting pad, and then
tighten an additional 1/ 4-3/ 4 turn. Do not overtighten.
Refill with oil of the correct API classification and
appropriate SAE viscosity grade for the anticipated
temperature conditions (refer to SECTION 6, STARTUP).Start engine and run for a short time to check for oil
leaks around the drain plug and filter element Stop
engine and check oil level. Oil level should be to the
FULL mark on the dipstick.

OIL AND FILTER CHANGE
Refer to Periodic Maintenance Schedulefor oil and filter
change interval. Change oil and filter more frequently if
engine operation includes extended periods of lowspeed operation or exposure to extreme dust and dirt.

Oil level should beto the "full" mark of the dipstick. Start
engine and run for a short time to check for oil leaks
around the drain plug.

H o i crankcase oil can cause bums H
bsEEEl
S H I M or sdaon s m no..
lingers and ha& clear whGn mmovlng the oil d&

The engine may beequippedwith a pressurizedcooling
system. This system will not operate properly unless it is
air-tight, without looseconnectionsor leaks. Otherwise,
pressurewill not be maintained,and lossof coolant and
overheating will result

Plug and wear protective clothing. New mnove dl
drain plug from a hot engine.

COOLING SYSTEM

Cleaning

Proper operating temperature is maintained by a
thermostat located in the water outlet manifold.

Keep the batteries clean by wiping them with a damp
cloth whenever dirt appears excessive.

Contact with hot coolant can result in
serious burns. Do not bleed hot, pressurized coolant from a closed cooling system.

Prior to cold weather and extended storage (30 days or
more), drain, flush, and fill the cooling system. Run the
engine until it reaches normal operating temperature.
This allows the thermostat to open and assures the
solution is circulated throughout the entire cooling
system.

At ambient temperatures below O0 C
(32" F), when engine is not in use, sea
water side of marine cooling system must be drained.
This will prevent cooling system damage caused by
freezing.

If corrosion is present around the terminal connections, remove battery cables and wash the terminals
with an ammonia solution or a solution consisting of
1/4 pound of baking soda added to 1 quart of water.
Be sure the vent plugs are tight to prevent cleaning
solution from entering the cells.
After cleaning, flush the outside of the battery, the
battery compartment, and surrounding areas with
clear water.
Keep the battery terminals clean and tight. After making connections, coat the terminals with a light application of petroleum jelly or non-conductive grease to
retard corrosion.

Checking Specific Gravity
Cleaning
For efficient operation, the cooling system should be
drained, flushed. and refilled once a year.
To drain the system completely, the radiator drain and
the cylinder block drain, located on the right side of
engine, must be opened.
Clean the cooling system using a good radiator cleaning
compound in accordance with instructions furnished
with the compound.
To drain sea water side of marine cooling system
remove sea water hose from sea water pump outlet or
remove drain plug from sea water tube.
Remove front heat exchanger cover to clean debris or
sediment from sea water side of cooling system. Refer to
Periodic Maintenance Schedule for cleaning interval.
After the system is completely drained, close the drains.
refill as specified in SECTION 6. START-UP.

BATTERIES
Disconnect negative ground strap from the battery
before working on any part of the electrical system or
engine.

Use a battery hydrometer to check the specific gravity of the electrolyte in each battery cell.
Hold the hydrometer vertical and take the reading.
Correct the reading by adding four gravity points
(0.004) for every five degrees the electrolyte temperature is above 27" C (80" F) or subtracting four gravity
points for every five degrees below 27" C (80°F). A
fully charged battery will have a corrected specific
gravity of 1.260. Charge the battery if the reading is
below 1.215.

Checking Electrolyte Level
Check the level of the electrolyte (acid and water
solution) in the batteries at least every 200 hours of
operation.
Fill the battery cells to the bottom of the filler neck. If
cells are low on water, add distilled water and
recharge. If one cell is low, check case for leaks. Keep
the battery case clean and dry. An accumulation of
moisture will lead to a more rapid discharge and battery failure.

I,,

Do not add water in freezing
uniew the engine is to be
run- long! enough (two or dhme hours) to assure a
thorough mixlng of water and electrdyte.
&% -

~irconnect
pobiive terminals bef&e charging batteries
to avoid damaging alternator or regulator.
Ignition of e x p h h bdhry gates
can cause s e m pwsonal injury. Do
not smoke while servicing brtteries.

If the engine is to be stored for more than 30 days,
removethe batteries. Wtth the electrolyte level at the
bottom of the split ring, charge the battery before
storing it. After every 30days the battery is in storage.
bring it back up to full charge. To reduce selfdischarge, store the battery in as cool a place as
possible so long as the electrolyte does not freeze.

FAN BELT

Fuel injection Pump

To adjust, loosen alternator bolt that passes through
elongated slot in mounting bracket. Slide alternator
until the correct fan belt tension is obtained. See
SECTION 9, COOLING SYSTEM for belt tension.
Tighten alternator mounting bolt to lock alternator in
place. Recheck tension; repeat if necessary.

FUEL SYSTEM
Due to the proelse tolemnces of
d b d lnlectlon systems9 It /s extremely Impodant the fuel be kept clean and free o i
water. Old or water In the system might cause severe
damage to both the Inlectlon pump and the lnlectlon
nozzles.

Fuel Filter
The combination primary and secondary fuel filter is
a disposable type. Any dirt that passes through the
primary section is trapped by the secondary section.
This prevents dirt from entering fuel injection pump.
The filter replacement interval will vary according to
the fuel quality and cleanliness. Using the wrong fuel
or dirty fuel will shorten the service life of the filter.
Refer to the Periodic Maintenance Schedule for the
recommended filter change interval. However, if the
engineshows signs of fuel starvation (reduced power
or surging), change the fuel filter. Use the following
procedures to replace.
1. Close the fuel tank shut off valve.
2. Clean all dirt from around filter, filter base and
surrounding area.
3. Disconnect negative battery cable from batteries.
4. Remove filter retaining clip or clips from fuel filter
(see Figure 2).
5. Remove old filter and dispose of it properly.
6. lnstall new fuel filter. Installretaining clip, make sure
retaining clip does not contact glow plugs or wiring.
7. Open fuel tank shut off valve, if used.
8. Prime fuel system.

Onan does not recommend washing
the dlesel englne. However, M you
must wash the englne, do so only when the englne k
cold. Never was a warm, hot, or runnlng englne.
Spraying water or cleaning solutions on a warm
englne or lnlectlon pump can cause sertous damage
to the englne fuel system.
Before leaving the factory, all engines are equipped
with carefully calibrated fuel injection pumps which
have been adjusted to a factory approved power
setting. Injection pump and aneroid adjustments are
preset and sealed at the factory. Preset adjustments
should not be disturbed.
Adjustments to Inlectlon pump or
anerold that do not meet spec*
lcatlons may vlolete Fedeml, state, and/or local
regulations. Emlsslonsand mechanical wammty may
also be volded by adjustmentsmade, that do not meet
specIfIcatlon8. Adjustments made by non-authorized
personnel may void mechanical warranty.
Do not cut seals on the throttle stop
Ithrottle
pamoN stop scmm
I scmwa.
Improper adlustmennh of
can cause permanent englne
damage. Tampering wlth sealed adlustmenh wlll
vow warranty.

HIGH IDLE

ADJUSTING SCREW

SPEED CON1ROL LEVER
(SPRING LOADED)
LOW IDLE
'ADJUSTING SCREW

FIGURE 3. STANADYNE INJECTION PUMP

All injectionpump sentice and adjustments must ba &no by qualifkl
&@tion p r r ~ n p#mice persmml. Topmwnt possible
equipment damage, it is imperative that service
personnel be qualmd.

RETAMING
'

n-im

CUPS

RETAINING
CUP
'

FIGURE 2 FUEL FILTERS

FS-liO

ff 'kigine has beon operating while
/
o f t h e , glow phg damage may
result. RwR itijodon rbcimp timing and check or
BCnUTK)N

replace glow plugs.

lubricationor regularly scheduled service, checks,
are requiredon the injection pump. If engine speed is
irregular, check fuel system and all other engine
adjustments before having fuel injection pump settings checked by a qualified service dealer or distributor. Injection pump dealers or distributors are
equipped with injection pump test stands, special
tools requiredfor repairing, testing, and adjusting the
pump. Adjustment of injection pump and aneroid for
optimum performance and low exhaust emissions
requires highly specialized equipment and special
training. If at any time the injection pump needs
repair or adjustment, it should be taken to an authorized injection pump service dealer or distributor. It is
important that the servicing dealer be furnished with
the pump model number, as well as engine model and
serial number, to facilitate the repair.

VALVE CLEARANCE

CRANKCASEBREATHER
(Turbocharged Engines)
Clean crankcase breather each time valve clearance
adjustments are made. Refer to the Periodic Maintenance Schedule for the recommended cleaning
interval. Use the following procedure when cleaning
crankcase breather.
1. Remove breather cap and' lift out the breather
element (Figure 4).
2. Clean breather cap and element in cleaning
solvent. Dry thoroughly with low pressure (under
241 kPa [35 psi]) compressed air.
3. Install a clean or new breather element in the
valve cover. Do not pack element in valve cover.
4. Install clamp, breather cap, and connect breather
tube.
Overtlghtenlng of the clamp wlll
tmrbmth~ap.

BREATHERCAP

BREATHER
ELEMENT

C o m t valve cloatance b very lmpopont In d l u ) engine pertomance, bacau8e of the hlgh c o m p ~ dwelopd
n
In
the cyllndem. lncomct v a h cl.mnce wlll cau88
1088 of comprwrlon, mltfldng, nolae, a d m a y eventually I d to damaged .ngIne compomtn

PERIODIC MAINTENANCE SCHEDULE
Followa regularschedule of inspectionand servicing,
based on operating hours. Keep an accurate logbook
of maintenance, servicing, and operating time. Use
the factory recommended Periodic Maintenance
Schedule (based on favorable operating conditions)
to serve as a guide to get long and efficient engine
life. Regular service periods are recommended for
normal service and operating conditions. For continuous duty, extreme temperature, etc., service more
frequently. For infrequent use, light duty, etc., service
periods can be lengthened accordingly. Neglecting
routine maintenance can result in engine failure or
permanent damage. Refer to OPERA TORS MANUAL
for Periodic Maintenance Schedule.

AIR CLEANER
A variety of air cleaners are available and used on this
series of engines. The required service interval.
regardlessof the type of air cleaner used, depends on
the amount of foreign material in the air surrounding
the enaine.
Inspect the air cleaner body periodically for dents
and cracks. Check for damaged gaskets and hoses.
loose hose clamps, and for leaks that would allow
unfiltered air to enter the engine. Correct any such
condition by the immediate repair or replacement of
the faulty parts.
Some dry type air cleaners are equipped with a filter
service indicator. Service or replacethe filter when so
indicated. However, if a service indicator is not used,
refer to the equipment manufacturer's operators
manual for specific air cleaner service instructions.

TURBOCHARGER
No calibration or adjustment procedures are possible
on a turbocharger in-service. Since all lubrication
requirementsare supplied by the engine, no periodic
maintenance in the usual sense is required. Due to
the wide variation in operating modes and conditions
to which turbochargers are subjected, maintenance
procedures based on specific numbers of engine
operating hours, vehicle miles, or calendar periods
are not practical.

Ahmy8 allow engine to run at idle
tor at least 2
houm before rtopplng. This allom turbocharger to
cool gmdually and unlfomly, helplng to prevent
beadng ~ z u m .

IPCAUTK)hll spud without 1-

c-lor)
FIGURE 4. CRANKCASf BREATHER

8 Oil System
SUBJECT

PAGE

........................................ 8-1
.......................................................8-1
........................................ 8-1
.................................................. 8-1
....................................................8-2
...................................... 8-2
........................................ 8-2
................................................... 8-3
..................................... 8-3
.......................... 8-4
. ...................................... 8-4
..................................................8-4
............................ 8-4
........................................ 8-4
..................................................8-5
..............................8-5
........................................ 8-5
.................................................. 8-6
.................................................. 8-7
........................................ 8-7
.................................................. 8-7

OIL PRESSURE SYSTEM
OILPAN
Removal and Inspection
Installation
OILPUMP
Removal and Disassembly
Cleaning and Inspection
Assembly
CRANKCASE VENTILATION
IDLER GEAR AND SHAFT (Oil Pump Drive)
Removal and Inspection ;
Installation
OIL COOLER PRESSURE RELIEF VALVE
Removal and Inspection
Installation
OIL PRESSURE REGULATING VALVE
Removal and Inspection
Installation
OILCOOLER
Removal and Inspection
Installation
OIL SPRAY NOZZLE
Removal and Inspection
Installation
OILLINES

.....................................................8.8
.................................................8 4
.............................................................8 4
...............................................................8 4

OIL PRESSURE SYSTEM
Refer to SECTION 7, MAINTENANCE for additional
information relative to oil system. The lubrication system
is designed so that all internal parts are pressure
lubricated by a gear type oil pump. The pump is driven
by the crankshaft through an idler gear. It is located at
the front of engine behind the gearcase backplate.
Engines equipped with an oil cooler have an oil pump
pressure relief valve located in cylinder block just above
the oil pump. This relief valve is set to open when the
discharge pressure exceeds 827 kPa (120 psi) and
bypasses oil back to the oil pan.
Oil pressure is maintained by an oil pressure regulating
valve located in cylinder block main oil gallery at the
front. This valve also serves as the pressure relief valve
on engines that do not have an oil cooler. Oil pressure at
normal operating temperatureand full throttle should be
344 to 380 kPa (50 to 55 psi).
A bypass valve is located in the oil filter. If engine oil is
too thick to circulate freely through filter, or filter
becomes clogged, the bypass valve opens allowing oil
to flow directly into main oil gallery.

The oil pump draws oil from engine sump, through
suction screen and circulates it under pressure through
oil cooler (if applicable), across front of cylinder block to
the oil filter (Figure 1). Oil then flows into a main oil
gallery running along the block. Oil passages transport
oil from the main oil gallery to each main bearing,
connecting rod bearing, camshaft bearing and the idler
gear bearing. Piston pins and connecting rod bushings
are lubricated through a funnel shaped cavity located in
the top of each connecting rod. A sufficient quantity of
oil splashed in the crankcase catches in each cavity
keeping it full and feeding each connecting rod bushing.
On Spec A to C engines an oil line extends along the
cylinder head under the rocker arm cover spraying oil
onto rocker arms. Oil returning by gravity from valve
cover to oil pan lubricates the push rodsand tappets.
Beginning with Spec D engines, oil is fed from the third
cam bearing to an oil gallery runningthrough thetappet
bores. Oil enters the hydraulic tappets where it is
pumped through the hollow push rodsto the rocker arm
assemblies.

LS-1062

FIGURE 1. OIL FLOW SCHEMATIC DIAGRAM

OIL PAN
The oil pan is the reservoir for engine lubricating oil
and has a drain for regular oil draining. Capscrews
with Belville washers secure oil pan to engine. A
gasket is used to seal the oil pan to cylinder block,
gearcover, and rear seal plate.

Removal and Inspection
1. Remove drain plug from oil pan and allow oil to
drain from engine.
2. Remove capscrews and Belville washers securing oil pan to cylinder block, gearcover, and rear
seal plate.
3. Tap oil pan loose with a plastic or rubber mallet,
and remove oil pan.
4. Wash oil pan in cleaning solvent and clean gasket
sealing surfaces on oil pan and cylinder block.
5. Inspect oil pan for cracks or other damage.
Inspect drain plug boss for evidence of leakage
and damaged threads. Repair or replace oil pan if
necessary.

Instdb9)on
On naturally aspiraw ptgines, cylinder walls are
lubricated by s p h h grid w y c r ~ . & y - t h d w.
crankshaft and connecting rods. "On turbocharged
engines, oil is sprayed through nozzles onto the botbm
of each piston torool and lubricate'thepistor.cylinder
walls, and conrsecting rqd bushing. Oilthrown by drive
gears lubricates the gear train.
On engines equipped with a turbocharger, oil issuplied
to and returned from the turbocharger through external
lines.

1.. PIa ~$w~~gask&me@$
pan.
2. P*
&kw
on-cyfiylinder block and hold it in
,.position by loosely inserting a capscrew and Belviile w q h e f in each corner. Install remaining
capscrebs and Belvitk washers, but do not
tighten them until all capscrews are started, so
the oil pap can W i e d if necessary.
3. Tighten all capscrews securely to a torque of 11
Nm (8 Ft.-Lb.) starting at the center and work out
.to each end.

Do not overtoque
pan capldlstorf
PCAUTl
O
N
screw. ,
*
,
,
toque wlll
011 pan
it to leak.
011

Removal and Disassembly

causing

1. Drain engine oil and remove oil pan.
2. Remove capscrew that secures oil pickup support to cylinder block.
3. Remove the three capscrews and washers securing oil pickup to oil pump. Note location of the
shorter capscrew (Figure 3).
4. Remove remaining two capscrews and washers
from oil pump.
5. Remove oil pump housing with pump idler gear.
6. Loosen capscrew that secures oil pump drive
gear to input shaft.
7. Tap on capscrew with a soft hammer to free drive
gear from the input shaft. Remove capscrew,
washer and drive gear.
8. Remove input shaft and oil pump plate.

4. Install oil drain plug into oil pan and tighten
securely.
5. Fill oil pan to proper level with the specified
engine oil. Refer to SECTION 6, START-UP for
correct type and amount. Run engine and check
for oil leaks.

OIL PUMP
A gear type oil pump is mounted on the gearcase
backplate. Theoil pump (Figure 2) has a helical drive
gear that meshes with an idler gear located directly
below the crankshaft. The oil pump drive gear is
pressed onto a tapered driveshaft and is secured with
a flat washer and capscrew. A precision bearing
pressed into gearcase backplate supports oil pump
drive shaft.

Cleaning and Inspection
1. Wash all oil pump components in clean solvent.
Inspect all parts before installing pump. The principal wearing parts are the bushings, drive gears,
and pumping gears. If dirt and sludge have been
allowed to accumulate in the lubricating system,
oil pump gear wear may be rather extreme after a
short period of time. If oil has been kept clean and
oil filter serviced regularly, wear on these parts
should be slight.
2. Inspect pump gear teeth, drive gear teeth. pump
body (inside), oil pump plate, and drive shaft for
wear or scoring. Gear teeth, inside of the pump
body, and pump plate must all be smooth and
have no scratches, score marks, or rough spots. If
worn or damaged parts are found replace the
entire pump.

DRIVE SHAFT

FIGURE 2 OIL PUMP

OIL PICK-UP

- <

". .>

"-.

FWSlRE 3. OIL PICK-UP MOUNTING

9. Install oil pan and new oil pan gasket by following
the procedure described earlier in this section.
10. Fill engine oil pan to the proper level with the
specified engine oil. Check for oil leaks.

3. Check backlash between oil pump element gears.
Measureoil pump element gears end clearance to
body.
4. Inspect oil pump drive shaft and bearing for
excessive wear or scoring and replace as necessary. Use a dial bore gauge or a telescopic gauge
and micrometer to measure inside diameter of
bearing. Replace bearing if the clearance to oil
pump drive shaft is greater than specified. This
bearing requires no machining after installation.

CRANKCASE VENTILATION

Assembly
During normal operation, unburned fuel and water
vapor are formed in theengine. If allowed to condense,
these vapors become contaminating liquids that
drain into the crankcase. Purpose of the ventilation
system is to circulate fresh air through crankcase to
carry away these harmful vapors.

1. Position oil pump plate over pump shaft. Install
this assembly with pump shaft through gearcase
backplate.
2. Place a 15 mm (0.5906 inch) O-ring over pump
shaft, between oil pump drive gear and backplate.
Secure gear to shaft with capscrew and washer.
3. Place pump element gear into pump body.
Lubricate pump element gears with clean engine
oil. Mount pump with two flatwashers and capscrews, placed in top two mounting holes of the
pump housing. Do not torque until oil pickup tube
is installed.
4. Inspect and thoroughly clean oil pickup screen
assembly.
5. Place a new pickup gasket on oil pump. mount oil
pickup assembly, and tighten all oil pump mounting screws to the specified torque in two even
steps. Make sure oil pump turns freely after
torquing.
6. Secure oil pickup support to cylinder block with
capscrew and flatwasher.
7. Remove drive gear and O-ring. Make sure oil
pump turns freely.
8. Place drive gear on shaft and secure with washer
and capscrew.

If crankcase breather becomes clogged, vapors are
trapped within the engine. The resulting pressure
build-up will force oil past the crankcase seals,
dipstick, and valve cover gasket.
Crankcase ventilation on naturally aspirated engines
is achieved through internal breather tubes located
under the valve cover (Figure 4). If crankcase shows
signs of pressurization, clean breather tubes. Clean
the passages in cylinder head that lead to the valve
port area. Apply Loctite 325 to breather tubes and
install, if removed.
Crankcase ventilation on turbocharged engines is
achieved through an external breather, that is a part
of the oil fill cap. This crankcase breather must be
cleaned after every 400 hours of engine operation.
Remove breather assembly, clean breather with
cleaning solvent, allow to dry, and replace on engine.

FffiM?E 4. CRANKCASE VEN'TIUTION (N/A ENGINE)

*,A

A$?

,.-

> ~ '

.. ..

Installation

IDLER GEAR AND SHAFT
(Oil Pump Drive)

1. To install a new idler gear shaft, position it in bore
of backplate. Drive idler gear shaft in with a brass
hammer until it protrudes 17.1-17.2 mm (0.6730.677 inch) from the backplate surface.
2. Place idler gear on idler gear shaft and secure
with capscrew and washer. Check idler gear end
play.
3. Install gearcase cover. Refer to SECTION 13,
ENGINE DISASSEMBLY, Gearcase Cover Installation procedure.
4. Apply a bead of "RTV" Sealant to the junctions of
oil pan, gearcase cover, and backplate.
5. Install oil pan. Refer to procedureoutlined earlier
in this section.

The idler gear has a steel backed bronze bearing
pressed into it. This bearing is lubricated with engine
oil splashed by the rotating gears. The idler gear is
secured with a flat washer and capscrew that threads
into the idler shaft, which is pressed into gearcase
backplate.

Removal and Inspection
To gain access to idler gear the gearcase cover and
oil pan must first be removed from engine. Refer to
SECTION 13, ENGINE DISASSEMBLY, Gearcase
Cover Removal procedure.
1. Remove capscrew and washer from idler gear.
2. Remove idler gear from shaft.
3. Inspect idler gear for nicked, worn, or pitted
teeth. Replace if necessary.
4. Measure inside diameter of idler gear bearing.

Replace bearing if it is nicked, scored, or worn.
After pressing a new bearing into gear, bearing
must be reamed to the correct inside diameter.
5. Inspect idler gear shaft. If shaft is worn or scored
it must be replaced.
6. To remove a worn idler gear shaft thread a 8 mm
adapter into the shaft.
7. Install the end of aslide hammer into adapter and
remove idler gear shaft from backplate.

OIL COOLER PRESSURE RELIEF VALVE
(Engine With Oil Cooler)
A pressure relief valve is located in the cylinder block
above the oil pump. This valve bypasses oil back to
the oil pan when pump discharge pressure exceeds
826 kPa (120 psi).
When engine is being overhauled or oil pressue is
low, remove, clean, and inspect oil pump pressure
relief valve parts. To service relief valve gearcase
backplate must first be removed. Refer to SECTION
13, ENGINE DISASSEMBLY, Gearcase Backplate
Removal procedure.

Removal and Inspection
1. Using a snap ring pliers remove internal retaining
ring from relief valve (Figure 5).
RELIEF VALVE
ASSEMBLY

2. Remove relief valve piston and spring.
3. Wash parts in cleaning solvent and inspect carefully. The piston must slide smoothly in bore of
valve body.
4. Replace piston if it is scratched or shows any sign
of wear.

Installation
1. Lubricate piston and spring with clean engine

2.
3.
4.

lubricating oil.
Place piston over spring and insert spring first
into cylinder block.
Push piston and spring into valve body and hold
in place with a screwdriver (Figure 6).
Using a snap ring pliers, install retaining ring in
cylinder block.
Assemble Darts removed to aain access to Dressure relief valve by a direct re;ersal of the removal
procedure.

OIL PRESSURE REGULATING VALVE
An oil pressure regulating valve is located in the
cylinder block at the front lower right corner of main
oil gallery. Purpose of the valve is to maintain a stable
oil pressure in the lubrication system. When oil pressure at the regulating valve exceeds approximately
380 kPa (55 psi.), the valve piston is raised off its seat,
and oil is bypassed directly from cylinder block oil
gallery to oil pan.

RELIEF VALVE
PISTON

The regulating valve may not work properly if sludge
is allowed to build-up in the lubrication system. If
valve sticks in open position, a sharp drop in oil pressure will occur. If valve sticks in closed position, a
sharp rise in engine oil pressure will occur.
Remove, clean, and inspect oil pressure regulating
valve whenever engine is being overhauled. To service regulating valve the gearcase backplate must be
removed from the cylinder block. Refer to SECTION
13, ENGINE DISASSEMBLY, Gearcase Backplate
Removal procedure.

Removal and Inspection
Remove the regulating valve from cylinder block as
follows:
1. Using a hammer and punch, drive out regulating
valve retaining pin.

Be careful when removing retaining pin. Drjving removai'tooi
Into the pin born too far will damage block.
2. Remove washer, spring, and piston.
3. Wash valve parts in cleaning solvent and inspect
carefully for wear or damage. Replace any worn
or damaged parts.
4. Thoroughly clean valve bore in cylinder block.

SNAP RING

FIGURE 6. INSTA~~INGPRESSURE RELIEF VALVE

Installation
1. Lubricate valve piston with clean engine oil.

Install piston, spring, and washer (Figure 7).

2. Compress spring and washer while driving retaining pin into cylinder block (Figure 8).

FIGURE 7. REGULATING VALVE INSTALLATION

/ RETAINING PIN

FIGURE 8.
a .

RETAINING PIN INSTAUATION

OIL COOLER
The engine oil cooler, located on left side of engine,
consists of a cooling core and cover, which forms a
tank. The engine oil pressure pump circulates oil
through the cooling core while coolant circulates
through tank, around outside of cooling core, controlling oil temperature.
The cooling core consists of several thin plates which
dissipate heat from the oil to engine coolant. If the
proper lubricating oil maintenance procedures are
not followed, impurities will be depositied in oil
cooler that can restrict oil flow through the cooling
core plates. A drop in oil pressure due to oil overheating, usually indicates a restricted oil cooler. If
this occurs, oil cooler must be cleaned or replaced.
Various sizes of oil coolers are used, depending upon
the oil cooling requirements of the engine. The
number of plates in the cooling core determines the
amount of heat dissipated to the coolant. Baffles are
used in some oil coolers to control coolant flow.

Installation
When installing the oil cooler use new gaskets, and
be sure the socket head capscrews are. properly
torqued.
1. Position baffles (when used) in oil cooler cover,
with notches over cover mounting hole casting
bosses. Lower baffle has a hole that lines up with
coolant drain.
2. Place cover gasket on cover and set cooler core
onto cover.
3. Install gasket onto cylinder block lining up
elongated slot in gasket with elongated recess in
cylinder block.
4. Using the torque sequence (Figure 9), gradually
and uniformly tighten oil cooler sockethead capscrews to atorqueof 22 Nm (16 Ft-Lb). Retorque
oil cooler sockethead capscrews after two hours
of operation.

Removal and Inspection
1. Drain cooling system. (Remove drain plug from

oil cooler to drain coolant from oil cooler.)
2. Remove socket head screws that secure oil cooler
assembly to cylinder block and remove oil cooler
assembly.
3. Scrape off any gasket material remnants that
remain on block after oil cooler is removed.
4. Clean oil cooler cover and cooling core. Scrape
off any gasket material that remains on cover and
cooling core.
Replace the oil cooler when there has been an
engine failure and metal paticles may have been
drawn into the lubrication system. Do not attempt
to clean an oil cooler that has been contaminated
with metal particles.
S..lnspect all gasket surfaces for scratches and
nicks. Check surfaces of oil cooler for warpage
using a straight edge. Pressure test oil cooler
core for leaks as follows:
A. Secure oil cooler test fixture to cooler core
with capscrews and hex nuts.
6. Attach an air hose to regulator in fixture.
Submerge cooler in water. Test for leaks with
air pressureof not morethan 138 kPa (20 psi).
C. Any air bubbles observed indicate the cooler
core has a puncture or may be defective in
some other way. If cooler core is faulty it must
be replaced.
6. Replace any part that is severely scratched or
warped. If oil cooler core is badly clogged, a new
core must be installed.

LS-1040

FIGURE 9.

OIL COOLER TORQUE SEQUENCE

OIL SPRAY NOZZLE
Oil is sprayed onto the bottom of each piston for
cooling and lubrication on all turbocharged engines.
The oil spray nozzle is located in the cylinder block
below each cylinder (Figure 10).

Installation
1. Install new O-ring on oil spray nozzle.
2. Push nozzle into bore in cylinder block.
3. Secure oil spray nozzle to cylinder block with
special socket head capscrew.
Use of the incorrect oil spray

result in Interference wlth the crankshaft.

OIL LINES (Spec A to C)
When cylinder head is removed for service, the rocker
arm oiling tube should be flushed with solvent. Use a
fine wire (Figure 11) to clean the small holes.

OILING

FIGURE 10. OIL SPRAY NOZZLE

Removal and Inspection
Oil spray nozzles must be removed before doing any
cylinder bore refinishing. A dirty nozzle can be
cleaned by removing oil gallery plug from side of
block and pushing afine wire through nozzle, without
removing noule assembly.
1. Remove crankshaft. Refer to SECTION 13, ENGlNE DISASSEMBLY.
2. Remove special capscrew that secures oil spray
nozzle to cylinder block.
3. Remove oil spray nozzle from cylinder block.
Remove O-ring from spray nozzle.
4. Clean nozzlejet by passing afine wire through jet
and soaking in solvent.

pwoN
a

011 spmy n w r S allgnmmt I8
cdtlcal. N
I nozzle Is bent, crushed, or damaged In any way replace spmy not210 888embly.

FIGURE 11. ROCKER ARM OILING TUBE

Whenever the engine is disassembled or overhauled,
clean all oil galleries and drillings with a solvent and
dry with low pressure compressed air.

9 Cooling System
SUBJECT

PAGE

COOLING SYSTEM ...................................................... 9.1
ANTI-FREEZE AND CORROSION ......................................... 9.1
HIGH TEMPERATURE CUT-OFF SWITCH .................................9.1
MAINTENANCE .......................................................... 91
.
Draining Cooling System ................................................9.1

Cleaning and Flushing Cooling System ..................................9.1
Engine Water Jacket and Cylinder Head ..................................9.2
FILLING COOLING SYSTEM ..............................................
92
.
THERMOSTAT ...........................................................
9.3
Removal ...............................................................93
.
Testing ................................................................
9-3
Installation .............................................................9.3
DRIVE BELTS ............................................................
9.3
Removal. Inspection. and Installation ....................................93
.
Adjustment .............................................................9 4
ENGINE WATER PUMP ...................................................
94
Service ................................................................
94
Inspection ............................................................-9-4
Removal ...............................................................9-5
Installation .............................................................95
.
RADIATOR COOLED SYSTEM ............................................9.6
Coolant Circulation ..................................................... 9-6
Fanand Pulley .........................................................9-7
Radiator ...............................................................9-7
MARINE COOLING SYSTEM ..............................................98
.
..................................
HEAT EXCHANGER COOLING SYSTEM
9-8
Water Flow
96
Sea Water
99
.
Captive Water
9-9
Water Cooled Exhaust
99
.
Marine Water Pumps
99
.
Heat Exchanger
9-11

PURPOSE OF COOLING SYSTEM

MAINTENANCE

Purpose of the cooling system is to carry heat away
from hot engine components in order to maintain
proper running conditions and clearances. Overheating can severely damage engines. The cooling
system must carry off the excess heat.
Regulatingcoolant temperaturehelps keep the engine
at the optimal heat level for each operating condition.
After starting, the engine must warm up quickly.
During periods of peak output, it must be adequately
cooled.

Theentirecooling system including the block, should
be cleaned and flushed out every two years or 3000
hours. This is especially important prior to cold
weather conditions and when preparing engine for
extended storage (over 30 days). The cooling system
can work efficiently only when it is clean. A build-up
of rust and scale in cooling system slows down heat
transfer and restricts water flow.

Draining Cooling System
1. If engine is installed in a portable or mobile type

ANTI-FREEZE AND CORROSION
Corrosion can shorten engine life by plugging the
radiator or heat exchanger core, creating hot spots
near exhaust valves, and settling in low areas of the
block. The corrosive sediment prevents proper heat
transfer and holds heat in. Most metals used in
cooling systems are susceptible to corrosion damage
which can lead to coolant leaks and overheating.
To prevent corrosion, always use a mixture of antifreeze and water as an engine coolant; even when
freezing temperatures are not expected. In addition
to lowering the freezing point of water, anti-freeze
contains rust inhibitors that prevent corrosion. Most
anti-freeze manufacturers recommend a minimum
50-50 mix of ethylene glycol anti-freeze and water for
winter and summer in closed water systems, with a
complete change every year to prevent corrosion
build-up and more extensive damage.
Use soft water whenever available. Well water often
contains lime and other minerals which eventually
may clog the radiator or heat exchanger core and
reduce cooling efficiency.

HIGH TEMPERATURE CUT-OFF SWITCH
The high temperature cut-off switch shuts down the
engine if the coolant reaches a dangerously high
temperature. This normally closed switch senses
coolant temperature in the engine cooling jacket.
When engine temperature rises beyond a specific
point the switch opens, breaking thecircuit to the fuel
solenoid. When coolant temperature falls to a safe
operating range the switch closes, permitting engine
restarting.
Stopping of the engine due to action of the high
temperature cut-off switch is not a normal condition.
Examine the cooling system to determine the cause
of the overheating and repair as required.
Marine propulsion engines are normally equipped
with warning lights or alarms rather than cut-off
switches. to alert operator to high temperature
conditions.

of equipment, make certain engine is in a level
position to assure complete draining.
2. Remove filler cap and open radiator or heat
exchanger drain.

Avoid removing the pressure
/
cap until unit has cooled. If this
k impractical, the system may be opened while
hot If certain precautions are taken. While
wearfng rubber insuktd gloves for protection,
slowly open the cap allowing the pressure to
vent. Thk k necessary to avoid personal injury
from scalding coolant or steam.
3. Open block drain located on right sideof cylinder
block.
4. Remove drain plug from engine oil cooler, if
applicable.

Cleaning and Flushing Cooling System
To clean rust and scale deposits from the cooling
system, drain system (as previously described) and
then fill with clean water and cleaner solution. Use an
approved chemical cleaner (such as type used for
cleaning automotive cooling systems) and follow
instructions provided by the supplier.

Cleaningrolutlons typically contaln
strong chemicals that can cause
burns or other injury If u m d Improperly. Read all
warning label8 carefully before using.
When cleaning is complete, drain cleaning solution
and flush system. For best resultsengine and radiator.
or heat exchanger, should be reverse flushed. Allow
engine to cool as much as possible before flushing
with cold water.

Never pour cold mter into a hot
enphn. Doing 80 may crack the
hoad or tho cyllndor block. Do not oprste englne
without coohnt for wen a h w mlnutes.
Flush system if engine operation indicates clogged
passages or overheating.

To Flush Engine:
1. Drain cooling system, remove thermostats, (reinstall water outlet), and disconnect hoses at
radiator or heat exchanger.
2. Close all drain plugs and attach flushing gun
nozzle to water outlet. Restrict normal engine
coolant inlet line opening until system fills with
water, then apply air pressure gradually. Repeat
the process until water from cylinder block flow is
clean.

TACnmON

1
.

When flushing the coollng 8ystem using a flurhing gun and
air, do not exceed 50 kP8 (7 pal) of alr pressure.
Excesslve air pressure wlll damage the coollng
system.
3. Remove flushing gun.
4. Reinstall thermostats, hoses, drain plugs, and
refill system with proper coolant.

5. When flushing is completed, check system thoroughly for any leaks uncovered by the cleaning
operations.
To Flush Radiator:
1. Drain cooling system and disconnect radiator
hoses at engine.
2. Secure flushing gun in radiator lower hose with a
hose clamp.
3. Fill radiator with water. Be sure radiator cap is on
tight. Direct upper radiator hose away from engine
to minimize collection of water around engine.
4. Apply air pressure gradually to avoid damage to
radiator.
When tlu8hlng the coollng 8y8tem uring a flu8hlng gun and
ah, do not exceed 50 kPa (7 prl) of air p n u u m .
Excesslve alr prertun wlll damage the coollng
system.
5. Shut off air pressure. Fill radiator with water again
and apply air pressure; repeat until water comes
out clean.
6. Remove flushing gun.
To Flush Heat Exchangec
1. Drain cooling system and disconnect heat exchanger hoses at engine.
2. Secure flushing gun in lower heat exchanger
W e with a hose clamp.
3. Fill heat exchanger with water. Make certain fill
cap is on tight.
4. Apply air pressure gradually to avoid damage to
heat exchanger.
When flu8hIng the coollng rystom udng a flushing gun and
alr, do.not exceed 50 kPa (7 pri) of ai[,pmuure
E x c ~ ~ air
~ ~p m
vo
u u n will m
e the coding
sy8tem.

5. Shut off air pressure. Fill heat exchanger with
water again and apply air pressure; repeat until
water comes out clean.
6. Remove flushing gun.
7. Disconnectsea water hoses at exhaust elbow and
sea water pump.
8. Secure flushing gun in rear hose.
9. Fill heat exchanger core with water. Apply air
pressure gradually to avoid damage to heat
exchanger.
10. Shut off air pressure. Fill heat exchanger core
with water and apply air pressure; repeat until
water comes out clean.
11. Remove flushing gun.

Engine Water Jacket and Cylinder Head
External coolant leakage may occur at any of the
joints in the engine water jacket such as the drain
plugs, core hole plugs, or cylinder head joint. Since
expansion or contraction can aggravate leakage, the
block should be inspected both hot and cold while
the engine is running.
Internal leakage occurs when coolant passes into the
engine oil through a loose cylinder head joint or a
cracked or porous casting. The leakage is not visible
but may cause extensive damage to the engine.
Coolant mixes with the oil to form sludge which
causes lubrication failure. Heavy sludge acumulations
followed by sticking piston rings, valves, and tappets
are symptoms of internal leakage.
Sometimes internal leaks are small enough to prevent
coolant leakage but permit exhaust gases to enter the
cooling system. The exhaust gases dissolve in the
coolant, depleting the rust inhibitors and forming
acid which causes corrosion.

FILLING COOLING SYSTEM
1. Close all drains that were opened to drain system.
2. Fill system with a clean anti-freeze and water
solution until level is approximately one inch
below bottom of filler neck. To assure complete
filling of the cooling system the cylinder head and
block should be bled to prevent air lock. This can
bedone by loosening one of theplugs or senders
located in the water pump before filling. When
codant appears, retorque plug to 17 Nm (150 inIb) and finish fijling. An additional pocket of air
will remain in the cylinder head.
F) or
In extremely low temperatures, - 3 1 0 ' (-2S0
~
lower. it may be necessary to increase the
percentage of anti-freeze to provide adequate
protection against freezing. Follow suppliers
recommendations to determine amount of antifrqeze needed for protection against the lowest
temperature expected. Anti-freeze solution must
be able to prevent freezing of cooling system
during the coldest winter weather.

3. Start engine and operate for approximately 10
minutes or until thermostat opens. As coolant
circulates, air trapped in cylinder head will be
released.
Contact with hot coolant can
result in serious burns. Allow
cooling system to cool before releasing pressure.
4. Fill with additional coolant as required, so coolant

level is maintained to within one inch of fill
opening.
5. Shut down unit and replace pressure cap.

1. Suspend thermostat in a pan of clean water.
Thermostat must be completely immersed but
not touching bottom of pan.
2. Heat water gradually and stir so heat is evenly
distributed. Ci;eck water temperature with a
reliable thermometer.
3. Observe thermostat as temperature of water rises.
If it is functioning properly, it should begin to
open when the water temperature is within plus or
minus 3OC (5°F) of the nominal temperature.
Thermostat should be fully open at about 12O C
(22' F) above the nominal temperature.
4. The thermostat is not adjustable. If it does not
operate within the above limits, it must be
replaced.

THERMOSTAT
One or two thermostats may be used, depending on
engine cooling requirements. When two thermostats
are used, one is a bellows type and the other is a
bellows type with bypass. If only one thermostat is
used, it is the bellows type with bypass. The bypass
thermostat is located in the thermostat housing,
directly above the bypass passage.
The bypass thermostat is so positioned in system that
when closed, coolant flow from engine to radiator is
shut off. During periods of engine warm-up, coolant
is directed from engine thermostat housing, through
bypass passage in water pump housing, to inlet side
of water pump. Coolant then flows through engine
water jacket back to thermostat housing. When
coolant temperature reaches engine operating temperature the thermostat(s) starts to open. As the
thermostat(s) opens allowing coolant to flow through
radiator, the bypass closes.
Replace thermostat if it is broken, corroded, or sticks in
the open or closed position. If engine overheats or does
not reach and maintain a minimum operating temperature, the thermostat should be removedand tested as a
possible cause. Engines must not be operated without
thermostat(s) or with incorrect thermostat(s) installed.

Removal
1. Drain cooling system.
2. Remove capscrews that secure thermostat cover
to water pump housing.
3. Raise thermostat cover with radiator hose intact
and position it to one side.
4. Remove thermostat cover gasket and thermostat.
5. Clean, inspect, and remove any gasket material
from the thermostat cover and housing.
.

Testing

Nominal operating temperature of the thermostat is
stamped on thermostat body. Note this nominal
temperature before using.

Installation
1. Install bypass thermostat in thermostat housing

3.
4.
5.

so bypass plate is positioned above bypass
opening. In large body water pumps, install the
other thermostat in housing.
Place a new thermostat cover gasket on top of
housing.
lnspect thermostat cover and clean if necessary.
Position thermostat cover on housing and secure
with capscrews.
Refill cooling system with theappropriate mixture
of coolant.

DRIVE BELTS
The alternator, water pump, and fan (if used) are
driven simultaneously by the crankshaft pulley
through either a single belt or a matched pair of belts.

Removal, Inspection, and Installation
1. Remove fan guard or shroud, if applicable.
2. Loosen capscrews that secure alternator to
mounting brackets. Push alternator in so fan belt
or belts can be removed from alternator pulley.
Slip belts from water pump pultey and over fan
blades. Remove belts.
3. Inspect fan belts for excessiveslickness, oil soak,
wear, tear, cracks, and overstretching!: Replace
belts-%?,.they
are damaged, badly worn, or soaked
with grease and oil. When a matched pair of belts
is used and only one needs replacement, both
belts must be replaced to assure satisfactory belt
performance.
4. Install fan belts by slipping-belts over fan blades
and into pulley ,grooves.
5. Adjust pelts and reptace any parts removed to
gain access to belts.
9";

Adjustment
1. Inspect belts frequently and replace belts if they
are oil soaked, damaged, or badly worn.

2. Check tension of fan belts. With engine stopped
fan belt tension should be:
267 N (60 pounds)
Single belt
Dual belts
222 N (50 pounds)
3. To obtain proper belt tension, loosen alternator
adjusting bracket and mounting capscrew and
move alternator in or out as required (Figure 1).
4. Retighten adjusting bracket and mounting capscrew.

The water pump shaft and bearing assembly is sealed
and does not require additional lubrication. A drilled
opening in the pump body provides a drain for any
coolant which might seep past seal assembly. This
prevents coolant from coming in contact with water
pump bearing and relieves pressure build-up on seal
back. The shaft and bearing assembly is secured in
pump body by a press fit. The seal assembly is spring
loaded and is pressed into pump body, forming a
leakproof seal at this point. Proper positioning of
impeller on shaft creates a load on seal assembly,
forming a tight seal.
A pulley hub, pressed on front end of water pump
bearing and shaft assembly, serves to mount the
pulley.

CHECK TENSION HERE

Service
The water pump is constructed to provide long life
with a minimum amount of attention when proper
corrosion preventive coolant is used. Care must be
taken to keep grit and abrasive material from being
circulated through cooling system. Water containing
scale-forming materials isespecially harmful to pump
parts.
ADJUSTMENT

Inspection
FIGURE 1. FAN BELT AOJUSTMENT

ENGINE WATER PUMP
Two sizes of water pumps along with two different
impellers for each pump and a variety of pulleys are
used on L engines, depending upon the cooling
requirements.
A centrifugal type waterpump (Figurer 2) circulates
coolant through cooling system. The water pump is
secured to cylinder block with three capscrews and is
belt driven from the crankshaft pulley. Coolant is
drawn through pump inlet-opening by the impeller
and forced through outlet opening in backside of
pump into cylinder block. A gasket on water pump
outlet assures a leakproof connection. An O-ring is
used to seal cylinder headcoolant outlet to thermostat
housing.

The pump cannot be rebuilt and must be replaced as
a unit. Check condition of bearing and shaft assembly
by turning water pump pulley. If bearing feels rough
or binds, seal is leaking, or housing is cracked, the
pump must be replaced.

SOCKETHEAD
CAPSCREW
CAPSCREW

THERMOSTAT

COVER

BY PASS
THERMOSTAT

GASKET
BELLOWS
THERMOSTAT

BYPASS
THERMOSTAT

COOLANT
INLET

URGE BODY WATER PUMP

SMALL BODY WATER PUMP

FIGURE 2. WATER PUMPS

Removal
1. Drain cooling system. Refer to procedure out-

lined earlier in this SECTION.
2. Remove hose clamps and hoses from the water
pump inlet and thermostat housing outlet.
3. Determine if radiator must be removed in your
application before removing water pump. Remove radiator and fan shroud if necessary.
4. Loosen alternator capscrew at slotted end of

mounting bracket. Push alternator in to relieve
tension on belts and remove belts.
5. Loosen capscrews that secure fan and pulley to
water pump hub.
6. Remove capscrews, fan, and pulley from water
pump hub.
7. Remove capscrews and washers that secure

water pump to cylinder block and remove water
Pump.

Installation
1. lnstall O-ring and apply a small amount of grease

to O-ring and groove in water pump adapter on
cylinder head.
2. Place new gaskets on water pump and spacer.
lnstall pump assembly, securing with the three
capscrews.
3. lnstall pulley and fan to pulley hub using capscrews and flat washers.
U8e caplcmw8 of the c o m t
Refer to th. 8pp10@8te PARTS CATALOG for
cornct u p l c n w . Capscnw8 mrnt thread all the
way Into water pomp hub wi#hout coming In
cont.ctwtth ~ r p a n p ~ n g .
4. lnstall fan belts. Adjust fan belt tension and

tighten capscrew on alternator bracket. Refer to
Fan Belt Adjustment procedure.
5. Install radiator and shroud if they were removed
during the disassembly. Install radiator inlet and
outlet hoses and clamps.
6. Fill cooling system. Refer to Filling Cooling System procedure.

RADIATOR COOLED SYSTEM

COOLANT
TO

BYPASS
THERMOSTAT

The radiator cooling system includes the water Pump,
thermostat housing, engine oil cooler (if applicable),
radiator. hoses, cooling fan, pulleys, engine coolant
temperature gauge, and water passages in the
cylinder block and cylinder head.

A pressure cap pressurizes the cooling system which
raises the normal boiling point of clean water at sea
level (100°C/212' F)approximately 1.7' C per 6.9 kPa
(3°F per psi). Operating temperatures above the
coolant's boiling point will cause loss of coolant and
result in engine overheating. Altitude also affects the
point at which coolant will boil. The higher the
altitude, the lower the temperature at which coolant
boils. To estimate coolant boiling point at various
altitudes above sea level, deduct .8'C per 304.8 m
(1.So F per 1000 ft.) from the boiling point established
with a pressure cap at sea level.

BY PASS
PASSAGE

COOLANT
FROM
RADIATOR

FIGURE 3. ENGINE COOLANT CIRCULATION

Coolant Circulation
The water pump draws coolant from the radiator
through lower hose and forces it into the cylinder
water jacket. Coolant circulates through cylinder
water jacket, cylinder head, and thermostats and
flows back into the radiator. Coolant then circulates
down through the radiator while the fan blows or
draws air across radiator. Coolant is again drawn
from the radiator to be recirculated.
During engine warm-up the thermostat is closed.
causing coolant to bypass the radiator. Coolant flows
through a bypass passage (Figure 3) in water pump
housing to the water pump inlet and recirculates
through the engine until it reaches normal operating
temperature. Recirculation ensures a rapid and even
temperature rise of all engine parts durig warm-up.
When the thermostat opens, this bypass is blocked.
Coolant then circulates through the radiator and
engine.

The water pump used on L engines is a cetrifugal
type. It mounts on the front of the engine cylinder
block and is driven by a belt (or belts). Inlet to the
pump is from the lower radiator hose or thermostat
bypass passage. Outlet is through the water pump
housing into the cylinder water jacket.

Fan and Pulley

Radiator

The engine may be equipped with either a pusher
type or suction type fan, depending on application.
The fan pushes or pulls (depending on type used) air
through the radiator. Engine coolant is cooled as it
circulates through the radiator core. The fan, fan
spacer, and fan pulley are bolted to pulley hub, which
is pressed on the water pump shaft.

For cooling fan to provide positive air flow through
the iadiator core, a fan shroud is often used behind
radiator to direct air flow. An overflow tube is normally
connected to the radiator filler neck.

lnspectlon and Repalr:

Fan blades seldom require service unless damaged.
Bent blades cause inefficient cooling and affect fan
balance. An unbalanced fan mounted on the water
pump will damage the water pump bearing. In caseof
damage, the fan should be removed and replaced
with a new fan.

Removal, Insptlon, and Installation: The cooling
system may have to bedrained and radiator removed
prior to removing fan and pulley, depending upon
clearance between fan and radiator.

1. Use a pressure washer to clean radiator exterior

and to remove all foreign material from between
cooling cores and fins. Be careful not to bend
fins. Straighten any that may be bent.
2. lnspect radiator for clogging or leakage. The
radiator should be repaired only by qualified
personnel. Test radiator under water with compressed air at not more than 50 kPa (7 psi). Note
location of any air bubbles and solder leaks.

3. lnspect hoses for any deterioration or damage.
Replace as necessary.

1. Loosen fan belts so belts can be removed from

water pump pulley.
2. Remove capscrews and washers that secure fan
and fan spacer to pulley hub. Removefan and fan
spacer.
3. Slide fan belts off water pump pulley, and remove
pulley from water pump hub.
4. lnspect fan for cracks, loose rivets, or bent
blades. Replace fan if any of these conditions
exist.

5. lnspect fan spacer and water pump pulley for
wear or damage. Replace if necessary.

6. Position fan spacer and water pump hub and
place fan belts in pulley grooves.
7. Install fan spacer and fan, securing with capscrews and washers.
8. Adjust alternator and fan belts to the proper
tension.

9. Install radiator and fan shroud. Refill the cooling
system if necessary.

Pms8ure Cap: A pressurized system permits operation of an engine at a higher temperature without
boiling off the coolant or losing it by evaporation. A
pressure cap permits coolant or steam to escape
when system pressure exceeds the pressure cap
rating. Boiling point of coolant increases as pressure
increases. To prevent damage to the cooling system
from either excessive pressure or vacuum, check the
cap periodically for proper opening and closing
pressures. If pressure cap is defective, replace it. A
pressure cap cannot be repaired.

HEAT EXCHANGER COOLING SYSTEM

MARINE COOLING SYSTEM
All Onan L Series Marine Diesel Engines make use of
flotation water for exhaust and heat exchanger
cooling. Although flotation water may be an ocean,
- lake, or river, the term "sea water" is used to describe
any flotation water that is drawn into the boat for
cooling purposes. Enginecoolant circulating through
a closed system is called "captive" water.
The heat exchanger cooling system was developed to
keep sea water, and the resulting sediment deposits
(salt, silt, etc.), from the engine cooling jacket. This
system has a fixed quantity of captive water in a
closed system to cool the engine. Sea water cools the
captive water in the heat exchanger. Sea water and
captive water are kept separated, so the engine water
jacket stays clean.
Because marine engines operate typically in very
small compartments, it is important that the heat
radiated from the exhaust system be kept to a
minimum. To accomplish this, the heated sea water is
discharged through the exhaust system. Special
mufflers, pumps, and anti-siphon devicesare required
to avoid interference with the passage of exhaust
gases and to prevent entry of sea water into the
combustion chamber.

Heat Exchanger Cooling has two separate water
systems, a captive water and a sea water system. The
metal impeller pump (engine water pump) circulates
captive water through cylinder head, engine block.
heat exchanger shell, water-cooled exhaust manifold,
and expansion tank.

A rubber impeller pump circulates sea water through
the heat exchanger core (cooling the captive water)
and out through the water-cooled exhaust. Figure 4
shows a schematic of a typical marine heat exchanger
cooling system.

Water Flow
During normal operation, marine cooling systems
take in more dirt and sediment than a radiator cooled
system. This contributes to water pump wear and
increases the possibility that water passages will
become clogged or restricted. It is very important that
water flow be checked frequently to insure that
adequate cooling is maintained.

EXHAUST MANIFOLD

HEATED WATER
FROM ENGINE BLOCK
I

BY PASS
THERMOSTAT

CS-lrn

PUMP

---+
.

BYPASS
THERMOSTAT

LEGEND

Sea Water Circulated
by Separate Pump
Captive Cooling
Water Circulated by
Engine Water Pump

FIGURE 4. HEAT EXCHANGER COOUNG

;.1-~.9-8

EXHAUST MANIFOLD
HEATED WATER
FROM ENGINE BLOCK

WATER
PUMP

CS-l2S8

Sea Water

Water Cooled Exhaust

The heat exchanger cooling system requires a
continuous flow of sea water for adequate cooling.
Anything that reduces or blocks the flow of water in
the sea water system may cause overheating. Remove
the filter screen from the inlet water filter on a
periodic basis and clean away any accumulations of
dirt and sediment. Flush clean water through the
screen before replacing the filter. Check all hoses
and pipes to make sure there are no kinks and bends
that could restrict water flow.

The marine exhaust system is designed so that a
minimum amount of heat is radiated from exhaust
system components. This is done to keep the heat
build-up in the engine compartment to a minimum.
Exhaust heat is dissipated by using a water cooled
exhaust manifold and a water injected exhaust pipe
and muffler system. The exhaust manifold is encased
in a shell through which engine coolant or sea water
is circulated. Just beyond the exhaust manifold, a
special elbow is fitted which allows the output water
from the sea water system to be injected into the
exhaust pipe. The injected sea water is carried out
through the exhaust system and discharged into the
flotation water.

When the boat is dry docked, the water inlet strainer
(normally located on outside of hull) should also be
checked for accumulations of debris and cleaned if
necessary. The water inlet should not be directly in
line with other water inlets as this could reduce the
amount of water received by the unit when the boat is
underway. If more than one inlet is present, they
should be staggered.

Do not use a scoop-@pe water lnkt
fitting. When the 608, is underway
and the engine h not running, sutflclent ram pressure
can force water past the sea waterpump, tloodlng the
exhaust system, and porslbly tloodlng the engine
cylinders.
Before starting, the sea water pump should be primed
and checked for water flow. The pump is primed by
removing the outlet hose from the pump connection.
Fill the pump and hose with water and replace the
components. With the engine running, check the
exhaust outlet to verify that the pump is delivering
water. An insufficient flow of water indicates that
there are obstructions in the system, the water pump
belt is loose, or the water pump is faulty. Inspect and
replace any hoses or pipes that have become restricted or blocked.

Captive Water
On marine cooled systems the engine water pump is
used to circulate engine coolant continuously through
the engine water jacket t.0 heat exchanger. Check all
hoses for kinks or bends tpat could restrict water flow
and make any repairs required.

Marine Water Pumps
Two types of marine water pumps are used: the metal
impeller engine (captive) water pump and the neoprene impeller (sea) water pump. Two types of
pumps are necessary because the water pumps are
used to perform different functions in the cooling
system. Metal impeller pumps provide no suction lift
but can operate in hot or cold water. Neoprene
impeller pumps provide a suction lift but can be used
only with clean cool water. Metal impeller pumps are
used for the captive water system and neoprene
impeller pumps are used for the sea water system. All
marine water pumps are driven by a belt from the
engine crankshaft.

Captive Water Pump: Check captive water pump for
wear or signs of leakage from the shaft seal. Loosen
drive belt and move the water pump pulley back and
forth. Pulley should be tight on the shaft and only a
slight amount of bearing play should be felt. Remove
pump if wear is excessive or if the seal leaks. Refer to
Engine Water Pump Removal and installation procedures.

Sea Water Pump: The mounting location and size of
the sea water pump may vary depending upon the
cooling and installation requirements of the application. Check sea water pump for wear or signs of
leakage from the shaft seal. Loosen drive belt and
m w e the water pump pulley back and forth. Pulley
should be tight on the shaft and only a slight amount
of bearing play should be feJt. Remove pump for
repair or replacement, if leakage or G a r is detected.

Removal and Installation:
4. Remove capscrew attaching water pump
to mounting bracket.
5. Install water pump by reversing removal
procedure.
6. Adjust belt tension. Refer to Drive Belt
Adjustment procedure.

1. Remove capscrew that attaches water
pump to adjusting bracket and loosen
capscrew that secures water pump to
mounting bracket.
2. Remove drive belt from pulley.
3. Loosen clamps and remove coolant hoses
from water pump. Remove capscrews
attaching pulley to water pump hub.

CAPSCREW

I
INTERNAL

RETAINING

PUMP

BEARING

1
I

SEAL
I

SHAFT

ASSEMBLY

WOODRUFF
KEY

END
PLATE

O-RING

HOUSING

FIGURE 5. SEA WATER PUMP

In8pectlon: It may not be necessary to disassemble the pump entirely unless a complete
rebuild is required. First determine cause of
pump failure.
TROUBLE
qump or

CAUSE
Worn or broken impeller.
cam, or cover.

-sin

Worn seal.
Worn bearing or shaft.

j t be replaced together. Do
r without the other. Inspect

PUMP

---

LEGEND

c Sea Water Circulated
by Separate Pump
Captlve Cooling
Water Circulated by
Engine Water Pump

dcking and signs of wear. The
riorates with time due to contin.g and must be replaced periodnpeller blades have broken, locate
.ove the particles or they will impede
rter flow. Particles will normally be
J at inlet to heat exchanger.
w c t the Pump body and housing for wear,
b ugh surfaces. or pitting and replace if any
of these conditions exist. Always use a new
end plate gasket and housing O-ring seal
when assembling pump.

Assembly:
1. Apply Permatex No. 1 on the backside of
cam and on cam retaining capscrew
threads. lnstall cam in pump housing.
Remove any Permatex that has gotten
into impeller cavity.
2. lnstall a retaining ring on the shaft in the
second groove from the keyway.
3. Press a ball bearing onto the shaft. (Push
the bearing on from the pulley hub end.)
Push bearing up against retaining ring.
Press only on the inner bearing race.
4. Place a spacer on the shaft against the
bearing. Press the second ball bearing
onto the shaft. lnstall a retaining ring over
the shaft against the second ball bearing.
5. If large internal retaining ring has been
removed from impeller end of pump
body, it must be installed at this time.
6. Press mechanical seal into pump body
from the impeller end. Make certain
mechanical seal is pressed in straight.
7. Push the bearing and shaft assembly into
pump body (impeller end first). Lock the
bearing assembly in place by installing
the other large internal retaining ring.
8. lnstall seat assembly, thrust washer. and
retaining ring overshaft from the impeller
end. Lubricate rubber part of seat with
clean engine oil. Install seat assembly
with white ceramic surface against the
seal.
9. Press brass woodruff key into pump shaft.
10. lnstall impeller in pump housing. Lubricate impeller with a silicone release agent
such as Dow Corning "Slipicone".
11. Place O-ring in groove of pump housing.
12. Position gasket and end plate on the
pump body and line up capscrew holes.
13. lnstall pump housing with impeller, on
pump body and secure with capscrews.

Heat Exchanger
L Series Diesel Engines use a water cooled exhaust
manifold with integral heat exchanger and expansion
tank. This minimizes the number of hoses and
connections required.
The number of tubes in the heat exchanger core will
change depending upon the cooling requirements of
the application. When replacing heat exchanger core,
always replace with one of the same size.

Fuel System
SUW ECT

PAGE

EXHAUST EMISSION LABEL ..................................... 10-1
FUEL SYSTEM OPERATION ..................................... 10-1

FUELFILTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2
....
10.2
Replacement
Fuel System Priming
10-2
FUEL INJECTION PUMP
10-3
STANADYNE DB2 INJECTION PUMP
10-3
Pump Adjustments
10-11
10-13
BOSCH VE INJECTION PUMP
INJECTION PUMP REPAIR
10-17
Fuel Shutoff Solenoid
10-17
INJECTION PUMP REMOVAL
10-18
INJECTION PUMP INSTALLATION AND TIMlNG
10-19
FUELLINES
10-21
FUEL TRANSFER PUMP
10-22
10-22
Maintenance
Removal and Disassembly
10-22
10-22
Inspection
Assembly and Installation
10-22
INJECTION NOZZLES
10-23
Operating Principle
10-23
NozzleTester
10-24
NozzleRemoval
10-24
10-24
TestingNozzle
Nozzle Opening Pressure Adjustment
10-26
Disassembly
10-26
Inspection and Cleaning
10-27
Assembly
10-28
10-29
Installation
INTAKE MANIFOLD
10-29
Removal
10-29
10-29
Inspection
10-29
Installation
AIRCLEANER
10-29

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ENGINE EXHAUST EMISSION
CONTROL INFORMATION LABEL
The lmportant Engine lnformation Label is located on
the engine valve cover of every EPA certified heavy duty
engine produced by Onan Corporation. The label
contains important emission specifications and setting
procedures.
When servicing the engine or emission system, the
lmportant Engine lnformation Label should be checked
for up-to-date information.
Ad)ustments made by nonquallfled
personnel may violate ~edera/,
s, te,
and/or local regulations. Emlsslon8 and mechanlcal
warranty may 8/80 be voided by adjustments made to
lnjectlon pump and anerold by non-quallfled personnel.

FUEL SYSTEM OPERATION
The fuel system consists of a fuel tank, water separator or fuel sediment bowl, transfer pump, combination primary and secondary fuel filter, fuel injection
pump, fuel injection nozzles, and fuel lines. There are
two fuel pressure systems, the low pressureand high
pressure.
The low pressure system consists of fuel tank, water
separator or fuel sediment bowl, fuel filter, transfer
pump, fuel lines between fuel tank and injection
pump, and fuel return lines.
The high pressure system begins in the fuel injection
pump where cam-actuated plungers force fuel into
the outlet ports. From the outlet ports fuel travels
through the high pressure fuel lines to the injection
nozzles.

Fuel is drawn by the transfer pump from fuel tank
through the sediment bowl or water separator, then
forced through the fuel filter to the injection pump. A
vane type transfer pump in injection pump forces fuel
to thecam-actuated plungers, which in turn force fuel
under high pressure through the fuel lines to the
injection nozzles from which fuel enters the combustion chambers in a fine cone shaped spray.
The fuel transfer pump delivers more fuel to injection
pump housing than is required for engine operation. A
line from the top of fuel injection pump returns surplus
fuel back to the fuel tank.
Lubrication for injection nozzles is provided by fuel
seepage between the lapped surfaces of each nozzle
valve and its body. Leaked fuel accumulates around
spindle in the spring compartment of each nozzle
holder, and is returned to fuel tank through a fuel
return line.
A regulating valve in the injection pump allows a large
share of fuel to be bypassed back to pump inlet side. The
fuel bypassed increases in proportion to engine speed.
The regulating valve is designed so transfer pump
pressure increases with engine speed.

Care must be taken in the storage of fuel, transfer of
fuel to fuel tank, and in keeping fuel tank full to prevent condensation. Dirt and water entering fuel system will damage fuel injection pump and injection
nozzles. The fuel filter is installed in fuel system to
clean the fuel before it enters fuel injection pump.
Ignition of fuel can cause serious
-explosion. Do notpersonal
injury or death by tire or
permit any flame, cigarette, or other
igniter near the fuel system.

FUEL FILTER
The combination primary and secondary fuel filter is
a disposable type. Any dirt that passes through the
primary section is trapped by the secondary section,
this prevents dirt from entering fuel injection pump.

Replacement
1. Close fuel tank shut off valve.
2. Clean all dirt from around filter, filter base, and
surrounding area.
3. Remove filter retaining clip or clips from fuel
filter.
4. Remove old filter and dispose of it-properly.

Due to the precise tolerances of
dlesel injecUon 8ysbms, it 1s
extremely Important the fuel be kept clean and
free of water. Dlrt or water In the system can
cause severe damage to both the Injectlon pump
and the Injection nozzles.

lPCAUTIOE(I

5. Install new fuel filter and prime fuel system.

Fuel System Priming
The fuel system must be primed: (1)whenever filter is
changed, (2) if there is air in lines, (3) engine has run
out of fuel, or (4) prior to initial start-up. For additional priming information see SECTION 6,
START-UP.
I. Priming (transfer pump, fuel filter, and injection
pump housing) low pressure fuel system.

A. Check fuel level in fuel tank and open shut off
valve.
B. Loosen low pressure injection pump line at
injection pump fitting.
C. Actuate the fuel priming lever on side of
transfer pump until fuel flows from fitting. If
the camshaft transfer pump lobe is up, crank
engine one revolution to permit hand priming.
D. Tighten fuel line at injection pump inlet.

2. Priming High Pressure Fuel System

This part of the system is usually self-priming
since any air trapped in injection lines is usually
forced out through injection nozzles. If, however,
engine has run out of fuel, been shut down for an
extended period, or has had fuel injection lines
removed, it may be necessary to prime as follows:

A. Loosen fuel injection line connecting nut, attaching each line to corresponding nozzle
holder.
8. Place speed control in high speed position
and stop control in RUN Position.
C. Energize starting motor. (Do not operate
starting motor for more than 30 seconds at a
time without pausing two minutes to permit
starter to cool.)
D. When fuel flows from the end of all high pressure fuel injection lines, stop starting motor
and tighten connection nuts.

DUO to thepr~C/Se
tolef811ce8of

/BCAUTK)N diem1 Injection 8ptem8, It I8

extremeiy important the fuel be kept c h n and
free of water. Dlrf or water In the 8yrtrm q n
cause seven, damage to both the injocdlon pump
and the InjecUon nozzles.

Keep hands away from spray.
1penetrate
A ~ A W ' N G The discharge pressure can
the skin and can cause blood
poisoning or a serious skin infection.

FUEL INJECTION PUMP

STANADYNE DB2 INJECTION PUMP

Purpose of the injection pump is to meter and deliver
fuel accurately under high pressureto injection nozzles
during the required injection period. The pump is selflubricating, except for the drive shaft bearing which is
splash-lubricated by engine oil.

The Stanadyne 082 fuel injection pump incorporates
inlet metering and opposed plungers actuated by an
internal cam ring with automatic advance.

AwARN'NG and injection pump service and

To understandthe operating principles of the DB2 pump
one has to become familiar with the main components
and theirfunctions. Refer to Figure 1 for injection pump
components.

adjustments be done by qualified injection pump
service personnel. From the stand point of possible
injury and/or equipment damage, it is imperative that
service personnel be qualified.

The main rotating components are the drive shaft,
transfer pump blades, distributor head, rotor, and
governor.

Before leaving thefactory, all engines are equipped with
carefully calibrated fuel injection pumps which have
been adjusted to a factory approved power setting.

The pump drive shaft Dasses through the governor
thrust sleeve and washer into the distributor rotor in the
hydraulic head. The driven end of the rotor incorporates
two pumping plungers.

No lubrication or regularly scheduled service, other
than operational checks, are required on the injection
pump. If engine speed is irregular, check fuel system
and all other engine adjustments before having afactory
trained mechanic adjust fuel injection pump settings.

The plungers are pushed towards each other at the
same time by an internal cam ring through rollers and
shoes that are carried in slots in the rotor.

Onan recommends that all aneroid

The injection pump is driven by a gear that is secured to
the pump drive shaft with a hex nut. The injection pump
drive gear is driven by the idler gear, which in turn is
driven by the crankshaft gear.

METERING VALVE

HOUSING

FRONT

HYDRAULIC HEAD ASSEMBLY

TRANSFER PUMP BLADES

DISTRIBUTOR ROTOR

PUMPING PLUNGERS

INTERNAL CAM RING

END CAP
FUEL INLET
STRAINER

/
REAR
TRANSFER PUMP
PRESSURE REGULATOR
ASSEMBLY

FIGURE 1. INJECTION PUMP COMPONENTS

10-3

INLET PRESSURE

0 TRANSFER PRESSURE
HOUSING PRESSURE
INJECTION PRESSURE
LUBE OIL

yTRANSFER

INTERNAL
PUMP

REAR

TRANSFER PUMP
PRESSURE REGULATOR

INLET PASSAGES
PUMPING CHAMBER
HEAD CHARGING PORT
RADIAL
CHARGING
PASSAGE

ROTOR RETAINER

CONNECTING PASSAGE
DISTRIBUTOR ROTOR
RADIAL PASSAGE

ELECTRICAL SHUT-OFF

BALL CHECK ASSY
AND BLEED ORIFICE

VALVE

FIGURE 2 CUTAWAY AN0 FUEL FLOW SCHEMATIC
"

10-4

The internal transfer pump (Figure 2) located at the
rear of the rotor, is a positive displacement vane type
and is enclosed by the end cap. A fuel inlet strainer
and transfer pump pressure regulator are also located
under the end cap. The distributor rotor has two
radial charging passages and a single axial bore with
one discharge port to service all discharge fittings to
the injection lines.
The hydraulic head assembly (Figure 1) contains the
bore in which the rotor turns, metering valve bore,
charging passages, and discharge fittings. Injection
nozzle high pressure lines are fastened to the discharge fittings.
A mechanical-centrifugal type governor controls fuel
delivery and, therefore, maintains the desired engine
speed within the operating range under various load
settings. The governor is driven directly off the pump
drive shaft without gearing. Governor weight centrifugal force is transmitted through a thrust sleeve to
the governor arm linkage and metering valve. The
metering valve can be closed to shut off fuel supply to
the distributor rotor (Figure 6).

The electric solenoid within the injection pump opens or
closes the metering valve to permit or stop the flow of
fuel. De-energizing the solenoid shuts off fuel delivery
and stops engine, since solenoid is of the energized-torun type (opens metering valve when energized). An
optional energized-to-stop fuel solenoid is used in
some marine applications.

As rotor turns, two rotor inlet passages register with
the charging ports in pump head, allowing fuel to flow
into pumping chamber. With further rotation, inlet
passages move out of re'gistry and the discharge port
registers with one of the discharge fittings. While the
discharge port is open, cam rollers (Figure 5) contact
the internal cam ring lobes, forcing plungers together.
Fuel trapped between plungers is then pressurized
and delivered to the combustion chamber.
Self-lubricationof the pump is an inherentfeature of the
082 design. As fuel at transfer pump pressure reaches
charging ports, slots on rotor allow fuel and any trapped
air to flow into the pump housing.
A vent wire assembly in the hydraulic head connects
outlet sideof transfer pump with pump housing. This
allows air and some fuel to be bled back to fuel tank
through the fuel return line. The bypassed fuel fills
pump housing, lubricates internal components, cools,
and carries off any small air bubbles in the pump. The
pump operates with housing completely full. A
housing pressure regulator (check valve) in the fuel
return line fitting maintains a housing pressure of 55
to 69 kPa (8 to 10 psi). There are no dead air spaces
anywhere in pump.

Fuel Flow: The mechanical or electric transfer pump
pulls fuel from the fuel tank (Figure 2). The transfer
pump pushes fuel through the filter, where it is
cleaned. The fuel is then pushed on to the injection
pump where it is pressurized and delivered to each
injection nozzle. Injection pump operating principles
are better understood by following the fuel circuit
during a complete pump cycle (Figure 2). Also, see
exploded view of rotor assembly (Figure 3).
Fuel is drawn from the filter through the fuel inlet
strainer by the vane type internal transfer pump.
Some fuel is bypassedthrough the pressureregulator
assembly to suction side of pump.
LEAF SPRING SCREW

Fuel, under transfer pump pressure, flows through the
center of transfer pump rotor, past rotor retainers into a
circular groove on rotor. Fuel then flows through a
connecting passage in pump head to the automatic
advance and up through a radial passage- to the
metering valve. Position of metering valve controlled by
the governor, regulates fuel flow into the charging
passage, which includes the head charging ports.

FGURE 3. ROTOR ASSEMBLY

Charglng Cycle: As distributor rotor revolves, two
inlet passages in rotor line up with the circular
charging passages (Figure 4). Fuel controlled by the
opening of metering valve, under transfer pump
pressure, flows into pumping chamber forcing plungers apart.
The plungers move outward a distance equal to the
amount of fuel required for injection on the next
stroke. At idle, when only a small quantity of fuel is

admitted into pumping chamber, plungers move out
a short distance. Maximum plunger travel and fuel
delivery is limited by the leaf spring contacting roller
shoe edges. When engine is operating at full load the
plungers move to the most outward position. Note
that while rotor inlet passages are in registry with the
ports in charging passage, rotor discharge port is not
in registry with a head outlet, also the rollers are off
the internal cam ring lobes.

PLUNGER
ROLLER BETWEEN
CAM LOBES

I
METERI/NG VALVE

CIRCULAR FUEL PASSAGE

TOR

INLET PASSAGE
CHARGING PASSAGE

TRANSFER PUMP PRESSURE
FS-1387

FIGURE 4.

HYDRAULIC HEAD ASSEMBLY-CHARGING CYCLE

Dkcharge Cycle: As distributor rotor turns, the inlet
passages move out of alignment with charging
passages. As rotor discharge port opens to one of the
discharge fittings, rollers contact the cam lobes
forcing shoes in against plungers and high pressure
pumping begins (Figure 5).
The beginning of injection varies according to load
(amount of charging fuel). As rotor continues to

rotate the rollers move up cam lobes pushing plungers
inward. During the discharge stroke fuel pressurized
between plungers flows through rotor passage and
discharge port to injection line. Fuel delivery to injection
line continues until rollers pass the highest point on cam
lobe and begin to move outward. As rollers move off
cam lobes, pressure in axial passage is reduced
allowing injection nozzle to close. This is the end of fuel
delivery.

CAM

DISTRIBUTOR
ROL.LER CON1ACTS

DISCHARGE FITTING

DISCHARGE PORT
DELIVERY VALVE

INJECTION PRESSURE
Fs-1388

FIGURE 5. HYDRAULIC HEAD ASSEMBLY-DISCHARGE CYCLE

Gowmoc The injection pump has a mechanical flyweight type integral governor which controls the
amount of fuel delivered to injection nozzles (Figure
6). By controlling fuel delivered to injection nozzles,
the governor maintains the desired engine speed
within the operating range under various load
conditions.

A speed increase due to a load reduction, increases
centrifugal force on the governor weights rotating
metering valve, reducing fuel flow. This limits the
speed increase (within engine operating range) to a
value determined by the governor spring rate and
throttle setting.

The governor obtains its energy from weights pivoting in the weight retainer. The weight's movement
against governor thrust sleeve rotates metering valve
by means of the governor arm and linkage hook. This
rotation varies metering valve opening registry with
passage to the rotor, controlling fuel flow. Centrifugal force tips the weights outward, moving governor
thrust sleeve against governor arm. The force of
weights against governor arm is balanced by the governor spring force, which is controlled by the manually positioned throttle lever for the desired engine
speed.

As load on engine is increased, the speed tends to
fall. Lower speed reduces force generated by the
weights permitting spring force to rotate metering
valve increasing fuel flow. Engine speed at any point
within the operating range is dependent upon the
combination of load on engine, governor spring rate,
and speed setting established by throttle position. A
light idle spring is provided for moresensitive regulation when the weight energy is low in the lower speed
ranges. The limits of throttle travel are set by high idle
and low idle adjusting screws.

On highway applications, direct control from the
accelerator to the meteringvalve is desired. For this type
of application a min-wax governor is used. A min-max
governor typically governs only in the engine low idle
speed range and at the maximum rated speed. At
speeds between the idle speed range and maximum
rated speed, the throttle lever directly controls metering
valve position.

A light tension spring on the linkage assembly takes
up any slack in linkage joints allowing metering valve
to close without having to overcome governor spring
force. Only a very light force is required to rotate
metering valve to the closed position.

LINKAGE HOOK

GOVERNOR SPRING
THROTTLE LEVER

1HROlTLE SHAFT

PIVOT SHAFT

SPRING CAPSULE

VALVE

GOVERNOR
THRUST SLEEVE
AND WASHER

Automatic Advance: The DB2 injection pump design
permits the use of a simple, direct acting hydraulic
mechanism, powered by fuel pressure from the integral
transfer pump. This feature is standard on all L engine
variable speed pumps. The hydraulic mechanism rotates
cam slightly and varies fuel delivery timing.

Cold Staff Mechanical Advance: Cold starting of
some variable speed turbocharged engines is improved by advancing the timing at cranking speeds.
This is done by extending the advance range above
the optimum timing required for operating speeds
below 2200 rpm.

Fuel delivery timing will normally retard with increasing speed due to the length of time required for
fuel to travel to injection nozzles. Use of an advance
mechanism allows earlier fuel delivery to injection
nozzles to insure optimum performance at higher
speeds and loads.

The cold start advance is operated by a lever located on
the injection pump (Figure 8). Cold start advance is
obtained by rotating the lever in a counter clockwise
direction.

1. Speed/Light Load Advance

(Hydraulic)
To obtain optimum performance both speed and
load timing is needed on some engines. This
advance gives normal advanced timing in the full
load speed range as well as further advance at
reduced engine loads.
2. Speed/Light Load Advance
(Mechanical)
This advance reduces emissions by increasing
injection timing at low throttle settings. Consequently this improves combustion efficiency at
lower engine speeds. This advance is used only
on injection pumps equipped with min-max type
governors.

When installing and timing injection pump, engine
cold start mechanicaladvance lever must be in the off
position.

COLD START
ADVANCE LEVE

FIGURE 8. COW START AOVANCE

FIGURE 7. MECHANICAL SPEED/LKlHT LOAD ADVANCE

Houdng P m w m Cdd A d w o (HPCA): The HPCA
located under the governor cover provides cold
cranking speed advance, as well as reduced white
smoke and hydro carbon emissions during warm-up.
By unseating the housing pressure regulator the
HPCA solenoidallowsadditionaladvancethroughout
the advance range. A thermo sensor located in water
pump housing controls HPCA solenoid operation.

When manifold pressure is at its peak, engine at rated
speed and load, the aneroid piston is pushed out
positioningits operating rod and pump shut-off lever in
the RUN position.' A reduction in intake manifold
pressureallowsthe spring loaded pistonto pull the lever
toward the shut-off position. As the lever is moved
forward, shut-off cam pushes linkage hook slightly to
the rear, reducing fuel flow past the metering valve
(Figure 10).

HOUSING PRESSURE REGULATOR
HPCA ON

GOVERNOR COVER

METERING VALVE

FIGURE 9. HOUSING PRESSURE COW ADVAKE

flGURE 10. ANEROID OPERATION

Aneroid (Acceleration Smoke Control): This is a
pressure sensitive fuel reduction control used on most
variable speed turbocharged engine applications. The
aneroid matches injection pumpfuel delivery quantity to
engine intake manifold pressure during periods of
acceleration.

As turbocharger speed increases intake manifold
pressure increases overcoming aneroid spring force.
The piston then pushes theshut-off lever to the full RUN
position allowing full load fuel delivery.

During the acceleration period the injection pump
delivers full load fuel quantity whila-the turbocharger
speed lags behind engine speedi W full turbo speed
is attained, insufficient air is supplied to the combustion
chambers for complete combustion of full load fuel
quantity. To prevent overfuelingand excessivesmoke, a
reduction in the full load fuel quantity delivered during
acceleration is needed. The aneroid senses intake
manifold pressure and reduces fuel quantity until
turbocharger gains speed and is abte to provide
sufficient air for efficient combustion.

Aneroid operation may bechecked with engine stopped
by connecting a regulated air pressure source to the
aneroid (boost pressure)inlet fitting. Becauseoperating
pressuresare very low, a mercury manometer is required
to measure the air pressure applied to the aneroid.
Increase air pressure and observe pump shut-off lever
(Figure 11). Clearance between pump shut-off lever.
forward screw, andst@ is preset at the fat4ory to 0.006
to 0.010 inch (0.1 5 100.25 mm) at 5 inchesof mercury on
automotiveengines, or 4 inchesof mercury on industrial
engines. Full pump shut-off lever travel should occur at
24 to 28 incyes of mercury. If pump shut-off lever does
not move, or an air leak is noted, aneroid must be
replacedas an assembly. Aneroid can bedisassembled,
but internal parts are not serviceable.

NOTE: Adjustments to injection pump that do not meet specifications
may violate Federal, state, andlor local regulations. Emissions and
mechanical warranty may also be voided by adjustmentsthat do not
meet specifications. Adjustments made by non-authorizedpersonnel
may void mechanical warranty.

PUMP

It is not recommended to make injection pump adjustments in the field. It must be clearly understood by the
owners and by Onan service personnelthat tampering
or inept repair attempts can cause irrepairable damage
to pumpsthat will not be covered by the manufacturers
warranties or exchangeagreements. Contact an authorized injection pump service dealer or distributor for
expert repair service on injection pumps.

Adjustments made by non-qualified
personnel may violate federal, state,
and/or local regulations. Emissions and mechanical
warranty may also be voided by adjustments made to
injection pumpandaneroidby non-qualifiedpersonnel.

LEVER
TRAVEL

Injection pump dealers are equipped with injection
pump test stands, special tools required for repairing,
testing, and adjusting the pump. If at any time the
injection pump needs repair or adjustment, it should be
removed and taken to an authorized injection pump
service dealer or distributor. It is imporrnt that the
servicing dealer be furnished with the pamp model
number, as well as engine model and serial number, to
facilitate the repair.
FIGURE 11. PUMP SHUT-OFF LEVER

IF PAINT SEAL ON ADJUSTMENT SCREWS IS NOT
BROKEN, ANEROID CAN BE REPLACED WITHOUT
REMOVING INJECTION PUMP FROM THE ENGINE. IF
ADJUSTMENT SCREWS ON PUMP SHUT-OFF LEVER
HAVE BEEN TAMPERED WITH (PAINT SEAL BROKEN)
SINCE CALIBRATION BY AN AUTHORIZED SERVICE
CENTER, INJECTIONPUMP MUST BE REMOVEDAND
CALIBRATEDAT AN AUTHORIZED STANADYNE SERVICE OUTLET.
Never submerge the aneroid assmMy in oi/ or solvmts. A dry lubricant
is used on the internal diaphragm. Washing of ihe
assembly will remove tho lubricant and possibly
damage the diaphragm.

The repair service should include cleaning, part replacement, static pressure tests for internal and external
leaks, internal pump timing, and calibration and adjustment to the manufacturer's specification.

CheckingEngineSpeed: Enginespeed may be checked
with a panel mounted tachometer if unit is equipped with
one. If unit does not have a panel mountedtachometer a
strobe light tachometer can be used.

.ACAUnoN
I

Injection Pump Adjustments
Fuel injection pumps ace adjusted at the factory for a
governor breakpoint of 40 to 60 rpm above rated speed
with a high idle setting of 7 to 10 percentgreater than the
specifiedspeed. The high idleadjusting screw is locked
and sealed at the factory. Pump adjustment is seldom
necessary. Low idle speed is factory set at 775 to 825
rpm. The low idle adjusting screw is not sealed; adjustment is permissible to achieve a suitable low idle
Speed.

1. Start engine and run until minimum operating temperature is obtained.

Rotating machinery can cause
se@ow p n o n a l&jury or deathS k y dear of rotating equipment and ensure that
protective shields and guards are in place.

&-NG

2. Move throttle control to both low and high speed
positions. Make sure control moves speed control
level on injection pump through its full arc of travel.

3. Move throttle control to low idle position and check
engine speed. Make sure engine rpm is within the
normal range 775 to 825 rpm. Low idle speed varies
depending upon engine application.
4. Move throttle control to high idle position. Check

engine speed. High idle speed should be 7 to 10
percent greater than speed stamped on injection
pump nameplate.
5. If engine speed is not within the specified ranges,
governor (speed control adjustment screws) must
be adjusted.

Speed Control Adjustments Standard 10 Percent
Regulation:
1 . Remove throttle control cable from fuel injection
pump speed control lever so lever can be moved by
hand.

2. With engine running at operating temperature.
loosen locknut (Figure 12) on low idle adjusting
screw. Push speed control toward front (fan end) of
engine so low idle adjusting screw touches lever
stop. Turn low idle screw in to increasespeed or out
to decrease speed. When low idle rpm is obtained,
hold adjusting screw and tighten locknut.
SPEED CONTROL LEVER (SPRING LOADED)
LOW IDLE ADJUSTING SCREW
HIGH IDLE

LOCKNUT

LEVER STOP

UEL INJECTION PUMP

High idle screw is factory set
and sealed. Only authorized
to make
Onan service personnel are
pump adjustments and re-seal the injection pump.
4. Connect throttle control cable to speed control lever
on injection pump. Makesurethat when throttle is in
the idle position, the control lever low idle adjust~ng
screw contacts pump housing lever stop. When
throttle is in the fast (high idle) position the high
speed adjusting screw must contact lever stop.

Speed Control Adjustments Optional 4.5 Percent
Regulation (Generator Application):An external speed
droop adjustment screw located at rear of injection
pump housing, controls governor sensitivity. The droop
screw adjustment varies the governor regulation by
changing the effective spring rate. This adjustment will
affect both full load and no load frequency settings and
may require that the high speed stop screw be reset.
After each adjustment of the droop screw, engine must
be shut down briefly in order to allow the governor
spring to unload and the adjusting mechanism to seek
its final position in the spring. Turning screw In shortens
control spring making it less sensitive and increases
speed droop. Turning adjusting screw out has the
opposite effect. Speed droop is the injection pump's
ability to respond to changing engine loads. Adjust
governor as follows:
1. Check engine operating speed. Adjust as outlined
in preceding procedure for standard governor.
2. To adjust speed droop:
A. Run engine until normal operating temperature
is obtained.
6. Apply full rated load. With engine running at
rated speed, droop is determined by removing
load and noting the no-load speed. In the case
of. a generator set note the difference in
frequency.
C. Turn adjusting screw, at back of injection pump
(Figure 13), clockwise to increase speed droop
or counterclockwise to decrease speed droop.
A small correction in throttle positon may be
necessary. Re-seal adjusting screws.
ELECTRIC FUEL SOLENOID
TERMINALS

FIGURE 12 SPEED ADJUSTMENT

3. With engine running at operating temperature
remove seal and loosen locknut (Figure 12) on high
idle adjusting screw. Push speed control lever
toward rear (away from fan) of engine so high idle
adjusting screw touches lever stop. Turn high idle
screw in to decrease or out to increase engine
speed. After correct high idle speed is obtained.
hold adjusting screw and tighten locknut

SPEED DROOP
ADJUSTMENT SCREW

FIGURE 13.

SPEED DROOP ADJUSTMENT

BOSCH VE INJECTION PUMP

screws. Hydraulic head assembly also contains the fuel
solenoid for interrupting the fuel supply, delivery-valve
assemblies, and delivery-valve holders.

In contrast to the Stanadyne 082 injection pump the
Bosch VE injection pump has only one pump barrel and
one pump plunger. Fuel delivered by the injection pump
is distributed via a distribution groove in the plunger to
the discharge fittings. The Bosch VE pump is of a
modular design and can be equipped with various
additional modules. This allows for greater versatility in
matching the pump to the engine.

A governor drive gear located on the drive shaft drives
the flyweight assembly. This assembly is equipped with
flyweights and a sliding sleeve.

The governor assembly consisting of the adjusting
lever, starting lever, and tensioning lever is mounted in
the pump housing. Governor assembly changes the
position of the control collar thereby controlling fuel
delivery.

To understandtheVE pump one has to become familiar
with the main components and their functions. Refer to
Figure 14 for VE injection pump components.

A hydraulic timing device is located on the underside of
the pump and is controlled by fuel housing pressure.

The drive shaft is supported by the pump housing and
drives the vane-type fuel supply pump. The cam plate
rides against the cam roller ring producing a rotating
stroke motion that is transferred to the distributor-pump
plunger. Distributor-pump plunger is guided by the
hydraulic head, which is secured to pump housing with

The pump housing is enclosed at the top by a governor
cover containing the control lever, speed adjusting
screws, and full load-delivery adjusting screw.

SLIDING SLEEVE

RATED-SPEED ADJUSTING SCREW
CONTROL-LEVER SHAFT

IDLE-SPEED ADJUSTING SCREW

GOVERNORSPRING
OVERFLOW RESTRICTION
ADJUSTING LEVER

GOVERNOR COVER
FLYWEIGHT ASSEMBLY

FULL-LOAD-DELIVERY
ADJUSTING SCREW
PIVOT FOR ADJUSTING

FUEL SHUTOFF

PUMP HOUSING

BLEEDER SCREW

CAM ROUER RlNG

ROLLERS OF CAM ROUER RING

LIVERY-VALVE HOLDER

EUMRY-VALVE ASSEMBLY

PLUNGER RETURN SPRINGS

DISTRIBUTOR-PUMP PLUNGER

FIGURE 14. VE INJECTIONPUMP COMPONENTS

Fcnl Flow: The mechanical or electric transfer pump
pulls fuel from the fuel tank (Figure 15). The transfer
pump pushes fuel through the filter, where it is cleaned.
The fuel isthenpushedon tothe injectionpump where it
is pressurized and delivered to each injection nozzle.
Injection pump operating principles are better understood by following the fuel circuit during a complete
pump cycle (Figure 15).
With each pump drive shaft revolutionthe integralvanetype supply pump, pumps a constant amount of fuel
from the fuel tank into pump interior, Pump interior
pressure is maintained by a pressure-regulatingvalve.
Interior pressure rises in proportionto engine speed. To
cool and automatically bleed the injection pump a
certain amount of fuel flows back to the fuel tank
through the overflow restriction located on the governor
cover.
Fuel flows from the pump interior through the inlet port
and metering slit in distributor pump plunger into the
high pressure chamber situated above distributor pump

plunger. As cam plate turns, riding over the cam rollers
in the cam roller ring, a rotating stroke motion is
transferredto the distributor pump plunger. The rotating
motion producesanopening and closingof the metering
slits and spill ports located in the distributor pump
plunger and hydraulic head assembly.
Pressure is produced by the stroking motion of the
distributor pump plunger after inlet port closes. Fuel is
deliveredand distributedthrough the distribution groove
to the individualoutlets. As the distribution groove lines
up with the outlet port high pressure lifts the delivery
valve assembly off its seat and fuel is forced through a
fuel injection line to the injection nozzle.
As distributor pump plunger spill port reaches control
collar edge fuel delivery is terminated. From this instant
on the high pressure chamber is connected to pump
interior through the internal port During the remaining
plunger stroke excess fuel is forced back into pump
interior.

FHLURO 15. VE FUEL FLOW SCHEMATIC

GovernocThe centrifugal governor is a integral part of
the distributor type fuel injection pump that controls the
amount of fuel delivered to the injection nozzles.
Direct control from the accelerator to the control collar
is required for most vehicle applications. For vehicle
applicationsa minimum-maximumgovernor (Figure 16)
is used. With the minimum-maximum governor only idle
speed and maximum full load speed are governed.
intermediate speed and load ranges are controlled
directly by the accelerator through the governor mechanism.
Engine speed is transmitted from injection pump drive
shaft through gears to the governor flyweights. As
engine speed increases centrifugal force moves the
flyweights outwards. The flyweights rotate around the
knife-edge bearing and move the axially displaceable
sliding sleeve. The sliding sleeve transfers the centrifugal force through a lever arrangement until the
system is in equilibrium against the force of various
springs.

Automatic Advance: To obtain optimum combustion,
maximum power, minimum fuel consumption,and clean
exhaust injection timing must be varied on diesel
engines operating over a wide speed range. This is
accomplished by the timing device which advances
injection timing as engine speed increases (Figure 17.)

CAM

SLIDER

TIMING-DEVICE
PISTON

PUMP HOUSING

INTERMEDIATE

PIN SHOULDER
CAM ROLLER RING

CONTROL LEVER

INTERMEDIATE

BORE IN TIMINGDEVICE PISTON

TIMING-DEVICE
SPRING
BALL PIN ON
STARTING LEVER

COVER

SUOER

SPILL PORT

nMING-DEVICE
PISTON

FIGURE 17. AUTOMATIC ADVANCE

DISTRIBUTOR-PUMP
PLUNGER

When engine is stopped injection pump timing device
piston is held in the basic position by a preloaded timing
device spring. During operation pump interior fuel
pressure is regulated in proportion to engine speed by
the pressure regulating valve in conjunction with the
overflow restriction.
FIGURE

j(C.

MINIMUM-MAXIMUM GOVERNOR

Starting and tensioning lever movement is transmitted
through a ball pin to the control collar which slides on
the distributor pump plunger. Control collar end face in
conjunction with the spill port controls the end of the
effective stroke and the quantity of fuel hpcted.
(

At a given engine speed interior pump pressure overcomes the spring force and moves the timing dev~ce
piston to the left. Axial piston movement is transferred
through the slider and pin to a rotatable cam roller ring.
This changes the respective positions of the cam plate
and cam roller ring causing the rotating cam plate to be
lifted earlier by the rollers.

Advance at the start of injection is accomplished by the
load dependent start of pump delivery (LFB). Purposeof
the LFB is to vary the beginning of pump delivery as a
function of engine load. The load dependent start of
pump delivery is designed so that when there is a drop
in load (full load to part load) injection timing is retarded.
As the load increases there is a reduction in engine
speed and the load dependent start of pump delivery
advances injection timing. The LFB is used to achieve
smoother engine running, reduce noise, and exhaust
emissions.

Cold Start Acceleratoc The cold start accelerator
advances the start of injection by a specific amount.
This operation is performed by the driver from the
passenger compartment via a cold start advance cable.
When the cold start cable is pulled the cold start
accelerator control lever and shaft are turned together
with the ball pin. This turning motion changes the
position of the cam roller ring with respect to cam plate
and advances injection timing.

Manifold Pressurn Compensator (LDA): This device
reduces the full load fuel delivery in the lower engine
speed range starting at a specified charge air pressure.
Fuel quantity in turbocharged engines is matched to the
increased air charge required during middle and upper
engine operating speed ranges (when turbocharger is
in operation). When the turbocharged engine is operating in the lower engine speed range, the air charge is
smaller and fuel quantity must be adapted to this
reduced air quantity.
During lower engine speed operation, the manifold
pressure compensation is inoperative until the charge
air pressure is sufficient to overcome the spring force.
As engine speed increases charge air pressure applied
to the diaphragm increases and the diaphragm and
sliding bolt with control cone are moved against the
pressure spring force. When the sliding bolt moves
vertically the stop lever rotates moving the control collar
allowing morefuel to bedelivered to match the increased
air quantity. At low engine speed or if turbocharger fails
the manifold pressure compensator returns to its basic
position and limits full load fuel delivery so that smokeless combustion is ensured.

P R E S S U R E SPRING

STOP LEVER

CONTROL CONE

-SLIDING BOLT
GOVERNOR COVER
GOVERNOR SPRING

TENSIONING LEVER

-STARTING LEVER

COMROL COUAR

INJECTION PUMP REPAIR
Before leaving the factory, all injection pumps are
carefully adjusted, calibrated, and sealed with paint or
wire seals. It must be clearly understood by the owners
and by Onan servicemen that tampering or inept repair
attempts can cause irrepairable damage to pumps that
will not be covered by the manufacturer's warranties or
exchange agreements. Authorized distributors and
dealers have the tool and seals to reseal injection pump
after making the necessary repairs.

Stanadyne DB2 Fuel Solenoid Replacement:
1. Remove fuel return lines and wire lead from fuel
shutoff solenoid.
2. Note location of ground strap on governor control
cover.
3. Remove capscrews, washers, and governor control
cover from injection pump (Figure 19).
4. Remove nuts, washers, and gaskets from fuel

solenoid terminals.
Pump or engine failures due to
tampering with seals or any other
unauthorized attempt to adjust or repair maximum fuel
adjustment setting, or high idle throttle stop screw will
void engine warranty.

Onan does not recommend washing
the diesel engine. However, if you
must wash the engine, do so only when the engine is
cold. Never wash a warm, hot, or running engine.
Spraying water or cleaning solutions on a warm engine
or injection pump can cause serious damage to the
engine fuel system.

5. Push solenoid out of cover.
6. Place a new fuel shut off solenoid in governor
control cover.
7. Place new gaskets over terminal posts and install
washers and nuts.

ACAUT'oN

8. Remove rubber gasket by pulling it out of groove in
cover.

9. Carefully place a new gasket in groove of governor
control cover.
10. Install cover and torque capscrews to 4 Nm (3 Ft.Lb.). Connect fuel return lines and make electrical
connections.
11. Install new wire seal through the guide stud, the
torque screw, and the cover screw.

Fuel Shut Off Solenoid
If there is fuel to the injection pump, but no fuel at
injection nozzle, the fuel solenoid may be defective.

GOVERNOR COVER

I
To check energized-to-run fuel solenoid operation,
listen for a click in injection pump when start switch is
placed In the run position. If no click is heard and there is
power to solenoid with the start switch in the run
pos~tion,the fuel solenoid must be replaced. To check
energtzed-to-stop fuel solenoid operation, listen for a
cltck in injection'pumpwhen start switch is placed in the
stop positiom: If no click is heardand there is no power to
sotecloidwith the start switch in the W p positon, the fuel
solenoid must be replaced.

A diesel engine cannot tolemte dM
or water in the fuel system. It is Ehe
maior cause of diesel engine failure. A tinypiece of dirt
or a few drops of water in the injection system may stop
your unit.

FIGURE 19. REMOVING GOVERNOR CONTROL COVER

Bosch VE Fuel Solenoid Replacement:
1. Remove wire lead from fuel shut off solenoid.

2. Remove fuel solenoid and O-ring from distributor
head.
3. Place new O-ring on new fuel solenoid.
4. Install new fuel solenoid with O-ring into the
distributor head.

5. Torque fuel solenoid to 42.5 Nm (31.5 Ft.-Lb.).

INJECTION PUMP REMOVAL
Clean all external surfaces of injection pump, including
all line connections and fittings that are to be disconnected. Clean area around injection pump mounting
flange and injection pump gear cover to prevent dirt
from entering crankcase.

Never clean the injectionpump when
II PCAUnON it
is hot, or even warm. To do so may
cause it to seize.

fuel as they am removed. BeforeInstalling new or
used partt, flush them thoroughly wlth dlesd
fuel, and Install whlle rtlll wet. Always wet flngen
wlth dlesd f u d before worklng with dlesel
lnjectlon sptem pa*.
7. The injection pump drive gear may be removed
through the cover plate opening in gearcase
cover or may be removed after gearcase cover
has been removed from engine. Determine if
radiator must be removed prior to removing injection pump cover plate, if radiator has to be
removed begin with Step A. When cover plate can
be removed without removing radiator begin with
Step 0.
A. Drain cooling system. Remove all components from front of engine, in order to facilitate the removal of injection pump drive gear
cover.

8. Loosen capscrew that secures alternator to
adjusting bracket. Push alternator in so that
fan belt can be removed from alternator
pulley.

1. Rotate engine until Number 1 piston is near the top

of its compression stroke and pointer in flywheel
housing is aligned with proper number of timing
degrees for the engine. On engines with front timing
indicator,notch in pulley must line up with center of
timing indicator.

2. Turn off ignition switch. Disconnect throttle control
cable from speed control lever on injection pump.

C. Remove capscrews and flat washers that
secure pump drive gear cover to gearcase.
Remove cover and O-ring.

0. Remove hex nut from injection pump drive
shaft.

E. Thread three (M8 x 30mm) capscrews into
injection pump drive gear. Install a slotted three
jaw puller onto injection pump drive gear
(Figure 20) and remove gear.

3. Disconnect electrical lead from terminal on fuel
solenoid and shut off fuel supply.
4. Remove fuel return lines from top of injection pump
and plug.

INJECTION PUMP

5. Disconnect filter to injection pump inlet line and
plug.

6. Remove all high pressurelines from injection pump.
Be sure to hold discharge fitting on injection pump
when removing high pressure line nuts. Remove
high pressurelines. Cover all openings with fuel line
plugs to prevent entrance of dirt.

A dImd engine cannot toler8te
dlrtorrnterln the M s p t u n .
It k one of the major causes of d l m l enghe
failure. A tfny piece of dirt ora few drops of water
in the Inject/on sptem may stop your unit. Men
opening any part of the fuel system beyond the
fuel filterf place ail part8 In-a pen of c h n d l m l

FS-1290

FIGURE 20. INJECTION PUMP DRWE GEAR REMOVAL

8. Remove the three hex nuts and washers that secure
injection pump to backplate.
9. Remove injection pump.

INJECTION PUMP INSTALLATION
AND TIMING
Accurate injection pump timing is essential for maximum
engine performance and operation. The injection pump
on each engine must be timed to that engine by using
the timing marks on engine (Figure21). All engine timing
is performed with engine not running. When a new
pump is ~nstalledon the engine, or after injection pump
has been serviced and is ready to be reinstalled, use the
following procedure.
1. Place a new injection pump O-ring on pump

mounting collar.
2. Position injection pump on mounting studs with
studs centered in mounting slots. Secure injection
pump to backplate with three flat washers and hex
nuts.
3. Stanadyne DB2 injection pump timing procedure.
A. Rotate crankshaft in a counterclockwise direction, when viewed from flywheel, until Number
1 piston approaches TDC on its compression
stroke. With the piston at TDC the crankshaft
can be turned 90' in either direction without the
valves on number one cylinder opening. If the

valves open during this test the crankshaft must
be turned one complete revolution (360') in the
direction of normal rotation. With number 1
cylinder at TDC continue to rotate crankshaft
until pointer in flywheel housing is aligned with
the proper number of timing degrees (Figure 22)
stamped on the flywheel. On engines with front
timing indicator, line up notch in crankshaft
pulley with timing indicator. Refer to Engine
Nameplatefor proper number of timing degrees
for the engine rpm stamped on injection pump.

A diesel engine cannot tolerate dirt. or water in the fuel
system. It is one of the major causes of diesel
engine failure. A tiny piece of dirt or a few
drops of water in the injection system may stop
your unit. When opening any part of the fuel
system beyond the fuel filter, place all parts in a
pan of clean diesel fuel as they are removed.
-

6. Clean dirt and foreign material from around
timing window cover on injection pump. Remove
timing window cover from fuel injection pump.
Two injection pump timing marks are used for
timing injection of fuel into Number 1 cylinder.
One mark is locatedon governor weight retainer
hub; the other is located on cam ring. Turn
injection pump shaft until timing marks are
aligned as viewed through the timing window
(Figure 22). Governor weight retainer must be
manually positioned in the counterclockwise
direction. Use a clean scribe or awl when
aligning cam ring and governor weight retainer.

FUEL INJECTION

FLYWHEEL TIMING MARKS

GOVERNOR
WEIGHT
RETAINER

FRONT TIMING
INDICATOR

PULLEY nMltw MARKS

FIGURE 21. ENGINE TIMING MARKS

FS-1279

FIGURE 22. INJECTION PUMP TlMlNG MARKS

C. Place injection pump drive gear on pump shaft.
lnstall hex nut and tighten to torque of 52 Nm
(38 Ft.-Lb.). Be careful when installing gear so
injection pump drive shaft does not rotate.

B. Position injection pump driveshaft so the key
slot points to discharge fitting for number one
cylinder (Figure 24). Use a Bosch coupling
wrench to turn injection pump shaft.

D. Rotate crankshaft back (clockwise when viewed
from the flywheel) one-half of a revolution. Turn
crankshaft in a counterclockwise direction until
pointer or timing indicator is aligned with proper
number of timing degrees or notch in pulley.
Refer to SECTION 1, SPECIFICATIONS for
proper timing setting.

E. Recheck alignment of injection pump timing
marks. If pump timing marks do not line up,
loosen the three pump mounting nuts and rotate
injection pump until timing marks are in alignment. Tighten injection pump mounting hex
nuts.

DRIVE SHAFT KEY SLOT
DISCHARGE FiTTING TO
NUMBER ONE CYLlhDER

F. lnstall timing window cover and gasket.

G. Apply a pipe sealant (with Teflon) to fuel supply
pipe threads. lnstall fuel return lines and filter to
injection pump inlet line.

FRONT VIEW

FIGURE 24. POSITIONING INJECTION PUMP

4. Bosch VE injection pump timing procedure.

A. Rotate crankshaft in direction of normal rotation
until cylinder number 1 begins its compression
stroke. Both valves of cylinder number 1 will be
seated during the compression stroke. Continue
to rotate crankshaft until 15 degree mark on
crankshaft pulley is properly aligned with the
pointer attached to the gearcase cover. Degree
marks are stamped with the value on front face
of crankshaft pulley.

Fuel discharged from discharge l i n g s can penetrate
skin and cause severe personal injury. Be
certain that discharge fittings are not aimed at
anyone whenrotating injectionpump driveshatt.

C. Remove bleed screw (Figure 25) and install
proper timing holder and dial indicator. Adjust
dial indicator for 1 to 2 mm of travel and secure.

INTAKE MANIFOLD
PRESSURE FITTING

CYUNDER

BLEED SCREW

FIGURE 23. ENGINE TIMING MMKS

FIGURE 25. BOSCH VE INJECTION PUMP TIMING

' Fuel penetration of the skin

can came severe personal
injury. Do not let the discharge fitting highpressure fuel spray against skin surfaces.
Cover discharge fittings or install high pressure
lines.

D. Use coupling wrench to turn injection pump
drive shaft clockwise as viewed from front of
engine until dial indicator shows the start of
plunger lift.

E. Place injection pump drive gear on pump drive
shaft. lnstall hex nut and tighten to a torque of
80 Nm (58 Lb.-Ft.). Be careful when installing
gear so injection pump drive shaft does not
rotate.
F. Rotate crankshaft counterclockwise (as viewed
from front), then clockwise to determine minimum dial indicator reading. Zero dial indicator
at this crankshaft position.

G. Rotate crankshaft clockwise to TDC. Loosen
three hex nuts that secure injection pump.
Rotate injection pump on mounting studs as
required to obtain plunger lift of 1.050
t0.050 mm at TDC.

5. When used connect flexible line from intake manifold to intake manifold pressure fitting on injection
pump.
6. lnstall high pressure lines. When securing high
pressure line nuts be sure to hold discharge fitting
to prevent over tightening of the fitting.
7. Connect electrical lead to nongrounded terminal on
injection pump cover. Connect throttle control to
speed control lever.

8. lnstall O-ring in groove in gearcase cover. Position
gear cover on gearcase and secure capscrews and
flatwashers.
9. lnstall and adjust fan belts. Refer to SECTION 9,
COOLING SYSTEM for correct procedures.

10. lnstall all components that were removed from front
of engine.
11. Fill cooling system to the proper level. Refer to
SECTlON 9, COOLING SYSTEM.
12. Prime fuel system. Refer to the procedure outlined
earlier in this section.

H. Recheck dial indicator zero and plunger lift at
TDC by rotating the crankshaft counterclockwise, then clockwise. Repeat preceding steps
as necessary to obtain proper timing of 1.050
t0.050 mm at TDC.

Do not strike end of injection
pump driveshaft to d r h shaft
out of the gear. Internal injectionpump damage
will result.
I. Torque injection pump mounting hex nuts.
Remove dial indicator and install bleed screw
with sealing washer. Torque bleed screw to
9 Nm (6.6 Ft.-Lb.).
J. lnstall fuel return line fitting (double-barbed)
and special hollow screw with overflow restriction orifice, marked "OUT"(Figure 25). Use a
copper sealing washer on each side of the
barbed fitting. Large barb points away from
engine. Torque hdiow screw to 20 to 25 Nm (15
to 18.5 Lb.-Ft.). lnstall nozzle overflow line to
small barb and tank return line to large barb.
lnstall hollow screw through the banjo fitting on
the filtered fuel supply line. Use a copper sealing
washer on each side of the banjo fittting. Torque
hollow screw to 20 to 25 Nm (15 to 18.5 Lb.-Ft.)

FUEL LINES
Inspect the fuel lines daily for loose connections,
breaks, or flaws. Any leak will indicate a failure or loose
connection.

Keepthe high pressureline connectorstorqued. Tighten
until snug, but do not strip the threads. To avoid bending
the lines or stripping the injection pump fittings, use a
flare Wows foot with torque wrench%r final tightening.
When replacing an injection line, besureto use a line
that is identical in size, shape, length, and inside
diameter. After removing an injection line it must be
protected with the appropriate fuel line plugs to
prevent dirt or moisture from entering the fuel line.

FUEL TRANSFER PUMP

Fuel Pump Removal and Disassembly

The fuel transfer pump (Figure 26) is a diaphragm
and relief valve type. The pump is operated by a
plunger driven off a cam lobe on the engine camshaft.
The fuel transfer pump maintains a positive pressure
to the fuel injection pump. Transfer pump output
pressure should be 27 to 48 kPa (4 to 7 psi) at engine
idle speed. Transfer pump pressure may be checked
by connecting pressure gauge and tee at the fuel
outlet.

CAPSCREW

1. Shut off valve at fuel tank. Disconnect pump inlet
and outlet lines.
2. Remove three capscrews that secure pump to
cylinder block and pull pump off. A special
wrench is available to aid in transfer pump
removal.
3. Notch pump cover and body with a file for location purposes when pump is being reassembled.
4. Remove hex head capscrew and cap. Loosen a
sticking cap by carefully inserting a punch into
capscrew bore and prying. Remove filter.
5. Remove the six cover screws. Tap pump cover
with a soft plastic hammer to separate the two
parts. Do not pry them apart, this may damage the
diaphragm.
6. Compress push rod spring against pump body
and remove retaining ring and spring washer.
7. Remove diaphragm assembly from pump body.

PUMP COVER

SCREW

DIAPHRAGM

Inspection
Clean all pump components and rinse with clean
diesel fuel. Use low pressure compressed air to dry
parts. Visually inspect pump components for
damage.
A kit is available for the replacement of gaskets,
diaphragm, and filter. If any other components are
damaged or worn, replace the pump assembly.

Assembly and Installation
PUSH ROD SPRING

~t-tml

FIGURE 26. MECHANICAL FUEL TRANSFER PUMP

Maintenance
If the diaphragm is leaking or broken, replace it and
check for diluted crankcase oil. Change oil if necessary. Remove and clean transfer pump filter after
every 2000 hours of operation. A damaged filter must
be replaced.

I . Lubricate diaphragm shaft and insert carefully
through oil seal into pump body.
2. Place spring and spring plate onto diaphragm
shaft. Compress spring and secure with retaining
ring.
3. Push diaphragm shaft upward against spring
force. Assemble cover to body with notch marks
lined up. Install screws, but do not tighten.
4. Release tension on diaphragm shaft and uniformly tighten screws to 2 to 3 Nm (17 to 26
in.-lbs.).
5. Position filter in pump cover with spacer legs
facing upwards.
6. Placegasket and cap on pump cover. Torque capscrew with gasket to 2 to 3 Nm (17 to 26 in.-lbs.).
7. Install pump on engine. Open fuel shut off valve
and primeiow preqswre fuel system.
8. Pressure test transfer pump output for correct
pressure.

INJECTION NOZZLES
The injection noule must inject an equal amount of
fuel into each cylinder, atomize the fuel, and spread
the fuel spray to mix it fully with the air for smooth
operation.
Type of Nozzle
The L diesel engine uses a hydraulically operated,
throttling pintle type of nozzle assembly.
The injection nozzle and nozzle holder is a simple
device. A spring is used to oppose injection pump
pressure until the right moment for injecting fuel, at
which time the nozzle opens.
Each nozzle holder assembly is adjusted to open at a
specific pressure. See Table 1.

TABLE 1. NOZZLE OPENING
PRESSURE
Naturally Aspirated
Turbocharged

13,000 to 13,800 kPa
(1890 to 2000 psi)
17,000 to 17,800 kPa
(2470 to 2580 psi)

Opening pressure can be adjusted by changing the
shim thickness in the nozzle holder.
Operating Principle
High pressure fuel from injection pump enters nozzle
holder fuel inlet and flows through drilled passages in
the noule body to the pressure chamber.

By first injecting a small amount of fuel, and subsequently a largeramount, combustion is more uniform.
Combustion pressures rise slower with this type of
fuel metering.
As soon as fuel injection pump stops delivering fuel
to nozzle holder assembly, nozzle needle returns to
its seat, cutting off fuel injection into combustion
chamber.
A certain amount of fuel seeps between the lapped
surfaces of nozzle needle and nozzle body; this is
necessary for lubrication. Excess fuel accumulates
around spring seat and in spring compartment of
nozzle. Excess fuel is returned to tank after each
injection cycle by a return line that connects nozzle
holder assemblies together. A fuel return fitting
combines the return fuel from nozzles with the flowthrough fuel from injection pump ball check valve. A
return line connected at this point returns excess fuel
to fuel supply tank.
Injection Nozzle Tester
Testing and adjustment can be performed only with a nozzle tester,
Figure 28. Do not affempt to dlsassemble nozzles or
adjust nozzle pressure without the proper test
equipment.
Nozzle assembly is tested with nozzle holder as a
complete assembly.
Absolute cleanliness is required when testing nozzle
holder assemblies.

IPCAUTK)N!

BODY
INLET
PASSAGE
NEEDLE

FIGURE 27. NOZZLE.ASSEMBLY

At the instant pressurized fuel i n the pressure
chamber (Figure 27) exceeds spring pressure on the
noule needle, injection begins as pressure lifts the
nozzle needle off its seat. Early in the injection
sequence the noule opens up only a narrow amount
(throttle gap) (Figure 27), allowing a small amount of
fuel to be injected into precombustion chamber.
This is called pre-spray. Due to the continuing
delivery of fuel by the injection pump, there is a
further rise in injection pressure, which lifts the
noule needle further, opening a larger throttle gap
and allowing a greater amount of fuel to be injected
into combustion chamber. This forms the main spray.

FIGURE 28. INJECTION NOZZLE TESTER

Check opening pressure, leakage, and spray pattern
using a nozzle tester. If any leakage or abnormal
spray pattern is detected, inspect with a magnifying
glass for erosion, scoring, etc. If cleaning with solvent
does not correct the malfunctions, a new noule
assembly will be required. Opening pressure can
then be set and the spray pattern checked.
Use test oil (Viscor 1487) in the injection noule
tester.

Nozzle Removal
1. Thoroughly clean injection noules, lines, and
surrounding area.

2. Remove high pressure lines and fuel return lines
from injection nozzles. Do not bend high pressure
lines when disconnecting. Cap all fuel line
openingsto prevent the entrance of dust, dirt, and
moisture.

3. Remove dust shields from injection nozzles.

Check for Nozzle Jamming: With the pressure gauge
by-passed, test noule for jamming by pressing nozzle
tester hand lever down quickly (about four to six
times a second). When nozzle valve moves properly,
noule will operate with a shrill whistle.
The spray pattern must be compact and well atomized
at full lift to be correct. The pressure difference
between start of nozzle opening and full lift causes
the fuel to emerge in a stream, change to flag-like
formations, and finally reach atomized spray pattern
at full lift with lever movements producing 4-6 noule
opening cycles per second. See Figure 29.

4. Remove injection nozzles from cylinder head
using a deep 27 mm socket.

5. Remove injection noule seals from injection
nozzle bore. Do not reuse injection nozzle seals.
They must be replaced whenever nozzles are
removed.

Testing Nozzle
CLOSED

Keep hands away trom a spraying
i *W*'N'NG
nozzle! The nozzle discharge pressure can cause oil to penetrate the skin and can cause
blood poisoning or a serious skin infection.

Connect injection nozzle assembly to the tester.
Make sure line fittings used to connect injection
nozzle assembly to tester are of the same type as on
injection nozzle assembly and tester.
When testing injection nouleassemblies asystematic
approach is recommended. There is a sequence of
tests to perform to insure a good injection nozzle
assembly; failure to pass any of the tests is reason to
reject an assembly. Do not combine test procedures
or results, and do not skip any tests.

SLIGHTLY OPEN
(PILOT SPRAY)
FULLY OPEN
(MAIN SPRAY)

FIGURE 29. NOZZLE SPRAY ACTION

Opening Pressure:Open tester pressuregauge valve.
Slowly (1stroke per second) depress pump lever until
nozzle ejects. Note nozzle opening pressure on
pressure gauge. See Table 1 for correct nozzle
opening pressure.
Nozzles with incorrect opening pressure should be
readjusted by changing shims.
An abnormal nozzle spray pattern or fuel stream is
normal when checking nozzle opening pressures.

i
i
7

1
-

Leakage Test: With the pressure gauge valve still
open, depress pump lever until the pressure is 1,034
kPa (150 psi) below the Specified opening pressure.

If a drop falls from the nozzle within 10 seconds, see
Figure 30, the nozzle leaks and must be cleaned and
retested. Nozzles that still drip within 10 seconds
must be replaced. Lapping is not recommended.

If no drops fall from nozzle tip within 10 seconds, as
shown in Figure 30, the nozzle is good.

ACCEPTABLE

UNACCEPTABLE

COURTESY OF ROBERT BOSCH SALES CORPORATION

FIGURE 30. NOZZLE LEAK TEST

Chalter Test and Spray Pattern: The chatter (noise)
test will indicate the ability of the noule needle to
move freely and properly atomize fuel.
Compare the chatter test and spray pattern for new
nozzle holder assemblieswith the Chatter Test Descriptions. See Table 2.

Used nozzles should not be evaluated for chatter at
lower testing speeds. An old noule can generally be
used if it passes the leakage test, chatters audibly at
high testing speeds, and ifit uniformly atomizes the
fuel.

I'ABLE 2 CHATTER TEST DESCRIPTIONS

Stringy, split streams that are not well atom~zedare
normal at 1-2 strokes per second.
issing noise from 2 4 strokes per second.
igh pitched sound only at 4-6 strokes per

Uniform and well atomized spray pattern
at 4-6 strokes per second.

Nozzle Removal
e nozzle
assure is
nd install
less than
3 thicker
iickness
kness of
change
i .80 to
steps of

1. Thoroughly cleal
surrounding area
2. Remove higb
from inject;
lines wk
openir
moic

Before startlng the disassembly ot a
fuel ln]ectlon nozzle holder, It Is very
Important to have a clean work bench, clean washlng
tluld containers, clean tools, and clean hands. Cleanllness Is emphaslzed because In]ectlon nozzle servlce
troubles are in most cases, due to dlrt enterlng the
nozzles. Use clean Ilnt-tree paper on work bench. A8
nozzle holder k disassembled, place components In
a container of clean diesel fuelas a protection against
dlrt and conoslon.

Do not attempt to dlsassembk the
nozzles or adjust nozzle pressure
wlthout the proper test equipment. A nozzle pressure
tester b essential to do a satisfactory lob.

,APLC

INJECTION NOZZLE SHIMS

PART NUMBER

THICKNESS (mm)

147-0617
147-0618
147-0619
147-0620
147-0621
147-0622
147-0623
147-0624
147-0625
147-0626
147-0627
147-0628
147-0629
147-0630
147-0631
147-0632
147-0633
147-0634
147-0635
147-0636
147-0637
147-0638
147-0639
147-0640
147-0641
147-0642
147-0643
147-0644
147-0645
147-0646

0.80
0.84
0.88
0.92
0.96
1.OO
1.04
1.08
1.12
1.16
1.20
1.24
1.28
1.32
1.36
1.40
1.44
1.48
1.52
1.56
1.60
1.64
1.68
1.72
1.76
1.80
1.84
1.88
1.92
1.96

Clean the outside of the nozzle holder and nozzle
before disassembling the nozzle holder assembly.
Removecarbon residuefrom nozzle needle tip, nozzle
valve body, and lower nozzle holder body with the
brass wire brush and a piece of hardwood (dipped in
test oil) found in the nozzle cleaning kit.
1. Clamp the upper nozzle holder body in avise (use
jaw covers). Loosen the lower nozzle holder body
with the appropriate wrench (Figure 31).

Dlsassembly
In most cases, disassembly and cleaning of the
injection nozzle is all that is required to place it in
good operational condition. The nozzle valve and
nozzle valve body are mated parts an'd must be kept
together. If replacement of either part is necessary,
both parts must be replaced as matched sets. Never
interchangecomponents between nozzle assemblies.

COURTESY OF ROBERT BOSCH SALES CORPORATION

FIGURE 31. NOZZLE HOLDER OISASSEMBLY

2. Remove noule holder from vise and disassemble
nozzle (Figure 32). Normally the nozzle can be
easily removed from nozzle holder. However, in
some cases it may be necessary to soak the
holder in fuel before nozzle assembly can be
withdrawn. Hold the nozzle needle by the stem
only. Perspiration and oils from the skin can
corrode the finely lapped surfaces of the needle.
STOP
PLATE

\
BODY

CLEANING NOZZLE RING

SPRING
PLT
!E

NEEDLE

FUEL LEAK
OFF FITTING

SHIM

NOZZLE
BODY

c >I-LOW FUEL LINE

.NNECTOR SCREW

NOZZLE
ASSEMBLY

CLEANING NOZZLE SEAT

FIGURE 33.
STOP
PLATE

LOWER
NOZZLE
HOLDER
BODY

NOZZLE
VALVE
BODY

NOZZLE
NEEDLE

SPRING
PLATE

SP~ING

SHIM

U+PER
NOZZLE
HOLDER
BODY

NOZZLE
ASSEMBLY

FIGURE 32.

CLEANING NOZZLE ASSEMBLY

NOZZLE AND HOLDER ASSEMBLIES

After cleaning, nozzle assembly should be dipped in
clean test oil and inspected.
Inspect tho nozzle needle tor: pounded or rough valve
seat area, worn or damaged pintle, score marks.
pressure marks, cavitation erosion, and damage from
fuel contamination. The pressure shoulder (Figure 34) will normally have an acceptable, rough
machined appearance.

PRESSURE
SHOULDER

VALVE
SEAT

Inspection and Cleaning
The nozzle needle and seat in nozzle valve body are
ground to provide a fine contact seat between the two
parts. Most wear occurs on the nozzle valve body
seat. The nozzle needleshould never be lapped to the
nozzle valve body seat. A nozzle cleaning tool kit is
required to clean a nozzle assembty property.
Clean the interior ring groove of the nozzle v a r ~ e
body with the scraper (Figure 33). Rinse in solvent to
remove all dirt and carbon residue, and dip in clean
test oil or diesel fuel.
COURTESY OF ROBERTBOSCH SALES CORPORATION

~efnoveburnt-on combustion deposits from all nozzle
assemblies with a commercially available cleaner.
Rinse all parts in clean test oil.

FIGURE 34. NOZZLE NEEDLE INSPECTlON

Inspect the nozzle valve body toc pounded or carboned seat, out of round injection hole. erosion,
excessive operating temperature, and corrosion.
All nozzles should be given the following slide test
after cleaning and inspection. Thoroughly rinse
nozzle assembly in clean diesel fuel or test oil. Needle
must fit freely in nozzle body. To check this fit, lift
needle about one third of its length out of nozzle
body. Needle should slide down to its seat by its own
weight when assembly is held at a 45 degree angle
(Figure 35).
If the nozzle fails the slide test, clean the nozzle again
and retest it.
Any nozzle needle and nozzle body assembly which
cannot pass this test must be replaced. The needle
valve and nozzle body are a matched set and must be
replaced as an assembly.

Assembly
Thoroughly rinse all injection nozzle components in
clean diesel fuel and assemble while wet. Always wet
fingers with diesel fuel before assembling injection
nozzle.
1. Set nozzle assembly into lower body.
2. Place stop plate in lower body with smooth, flat
side against nozzle assembly.
3. Placespring seat over nozzle needle in stop plate.
4. Insert shim into upper nozzle holder body.
5. Insert spring into upper body. Thread upper body
into lower body just enough to hold the parts in
place (several turns of the lower body).
6. Mount the upper nozzle holder body in a vise
(Figure 36) use jaw covers, and tighten lower
nozzle holder body to the specified torque.

NOZZLE

Qq'l
FIGURE 35.

NOZZLE ASSEMBLY SLIDE TEST

Rinse new nozzle bodies and nozzle needles in
solvent to flush thoroughly and completely remove
aH protective coatif&$naterial.
Worn or damaged parts must be replaced. Nozzle
needle and valve body are replaced together as an
assembly.
The premature failure of nozzle assemblies is in most
cases caused by improperly filtered air and fuel, fuel
contamination, excessive operating temperatures,
incorrect combustion pressures, improper nozzle
handling, and p o o m o u l e assembly and installation
procedures.

COURTESY OF ROBERT BOSCH SALES CORPORATION

FlGURE 36. NOZZLE HOLDER ASSEMBLY

7. After nozzle assemblies have been cleaned, inspected and given the slide test, the nozzle and
hdder assembly should be tested for opening
pressure, leakage, chatter, and spray pattern.

Keep hands sway from a spraying no&d Thenozzle discharge
pikasure can m u m 011to penetrate the skln and
can cause blood poisoning or s senlous skln
Infection.

Removal

Installation
1. Place new injectibn nozzte seals in nozzle bore
with concaveside down (Figure 37). Do not reuse
injection nozzle seals. They must be replaced
whenever nozzles are removed. Install injection
nozzles into cylinder head and tighten to the
specified torque.

1. Remove air inlet hose and air cleaner if necessary, from intake manifold flange.
2. Remove high pressure fuel lines from injection
nozzles. Loosen high pressure lines at injection
pump. Be sure to hold discharge fittings when
loosening lines.
3. Remove injection line clamps from intake manifold. Carefully pull injection lines away from
manifold.
4. Remove capscrews and washers that secure
intake manifold to cylinder head.
5. Remove intake manifold and manifold gasket.

Inspection
1. Wash and clean intake manifold in a good

solvent.
2. Check manifold for deposits, clean and remove
any obstructions found in manifold.
3. If manifold is cracked or mounting surface is
warped enough so that it will not seal, the manifold must be replaced.
4. Clean and inspect for warpage mounting surface
on cylinder head to make sure that it is smooth
and free of gasket material.
FIGURE 37. INJECTION NOZZLE SEALS

Installation

I n c o m t installation of the I n b tion nozzle seals WINcause the
injection nozzk to overheat and stick. Stlcky
nozzles cause excessive noise and smoke.

1. Place a new manifold gasket on manifold.
2. Mount intake manifold and torque capscrews to
23 Nm (17 Ft.-Lb.) in a pattern. from inside to
outside.
3. lnstall high pressure fuel lines. Refer to Injection
Pump lnstallation procedure.

2. Place dust shields over injection nozzles if used.

4. Connect or install air inlet hose and air-cleaner.

3. lnstall and connect injection lines and return
lines. Make certain lines are clean and dry before
installing them.
On marine engines torque 8 mm hollow fuel line
connector screw to 8 Nm (6 Ft.-Lb.). Torque
Banjo fitting retaining nut to 40 Nm (30 Ft.-Lb.).
Torque high pressure injection line nuts to 24 Nm
(18 Ft.-Lb.) on all engines.

The purpose of air cleaner is to remove dust, dirt, and
other foreign material from air used by the engine.
Engine life depends to a great extent on air cleaner
efficiency. Rapid wear on cylinder bores, pistons, and
rings will result if air cleaner is not kept in good
condition and properly serviced.

INTAKE MANIFOLD
The air intake system consists of those parts which
transport filtered air to the engine cylinders.
The air intake system has two basic components, air
cleaner and intake manifold. If engine has a turbocharger, the compressor side of turbocharger is part
of intake system.
It is important to provide an adequate supply of fresh
clean air to the combustion chambers. Insufficient air
supply will limit the amount of fuel engine can burn
and lead to loss of power, excessive smoke, and high
fuel consumption. Dirty contaminated air results in
worn engine parts, high oil consumption, and early
engine failure.

AIR CLEANER

A variety of air cleaners are available and used on this
series of engines. The required service interval,
regardless of air cleaner type, depends on the
amount of foreign material in air surrounding engine.

Some dry type air cleaners are equipped with a filter
service indicator. Service or replace filter when so
indicated. However, if a service indicator is not used,
refer to equipment manufacturer's operators manual
for specific air cleaner service instructions.
Inspect air cleaner body periodically for dents and
cracks. Check for damaged gaskets and hoses, loose
hose clamps, and for leaks that would allow unfiltered
air to enter the engine. Correct any such condition by
the immediate repair or replacement of the faulty
parts.

Exhaust System

SUBJECT

PAGE

.................................
..............................................
..........................................
..........................................

EXHAUST SYSTEM OPERATION
11-1
Exhaustsmoke
11-1
INSTALLATIONTIPS
11-2
EXHAUSTMANIFOLD
11-1
Dry Exhaust Manifold Removal ........................................11-2
Dry Exhaust Manifold Installation ...................................... 11-2
Exhaust Manifold Inspection .......................................... 11-2
Water Cooled Exhaust Manifold Removal
and Installation ..................................................... 11-2
'Water Cooled Exhaust Manifold and Heat
Exchanger Disassembly. Inspection .................................. 1 1 3
Water Cooled Exhaust Manifold and Heat
Exchanger Assembly
11-3

...............................................

EXHAUST SYSTEM OPERATION

Avoid sharp bends by using large radius elbows.

The exhaust system collects exhaust gases from
each engine cylinder and carries these gases to the
atmosphere. Theexhaust system consists of exhaust
manifold, gaskets, muffler, and exhaust piping. If
engine is equipped with a turbocharger, the turbine
portion of turbocharger is part of exhaust system.

Check back pressure with a mercury or water
column type manometer at the exhaust manifold
outlet.
Vent exhaust gases outside. Use flexible tubing
only between the engine exhaust outlet and rigid
piping.
Position exhaust outlet away from engine air
intake, windows, doors, air conditioners, and
other air inlets.

The exhaust system must efficiently e.xpel all combustion products and muffle exhaust noises with a
minimum amount of back pressure. If back pressure
is too high, the engine volumetric efficiency is
reduced, fuel economy drops, exhaust temperature
increases, and valve life is shortened. Any combustion products left in combustion chamber following
the exhaust stroke, dilutes the amount of air that can
be drawn in on the next intake stroke. This reduces
engine power and increases fuel consumption.

Exhaust Smoke
Alight gray or light blue smoke may bea result of low
ambient temperature and light load. This smoke is
unburned fuel (not harmful to the engine) and disappears when more load is applied.

On service calk, always Inspect
!PWARNING
exhaust systems for posslble Ieak8.
Report any exhaust hazatds to the owner/operator
and warn them of the potentlal dangers to Ilfe If not
repalred.

INSTALLATION TIPS
Points to remember when installing an exhaust system are:
Exhaust pipes should be as short as possible with
a minimum of fittings.
The muffler must be as close to engine as possible. Mufflers which are too far from the manifold
remain cool and collect carbon residue.

Exhaust noise can be suppressed or reduced by:
Using a heavy duty exhaust system with a more
efficient muffler.
Avoid long runs of flexible line.
Installing a deflector at the exhaust outlet to
direct exhaust toward the ground, but away from
operator.
Using a resonator in addition to a muffler.
The importance of exhaust systems (normally supplied by the customer) cannot be over-emphasized. A
poor or clogged system causes low power, overheating and engine damage. A poor exhaust system
increases back pressure which reduces efficiency,
causing low power and may result in overheating
thereby causing engine damage.
'

If an OEM manufacturer tailors Its
IAWA'N'NGI
own exhaust system, Onan Applied
Englneedng must approve the lnstellatlon for warranty purposes. A haklng exhaust system can result
In personal Injury or death.
Inhalationof exhaust gases can result
in serious personal injury or death.
Pipe exhaust outside the hull and do NOT terminate
exhaust pipe near any window or bulkhead door
openings.

IPH(ARNING1
EXHAUST GAS IS DEADLY!
Exhaust gases contain carbon monoxide, a poisonous gas that can cause
unconsciousnessand death. It is an odorless and colorless gas formed during
combustion of hydrocarbon fuels. Symptoms of carbon monoxidepoisoning are:
Dizziness
Headache
Weakness and Soapiness

Vomiting
Muscular Twitching
Throbbing in Temphr

If you experienceany ot these symptoms, get out into fresh air immediately,shut
down the unit and do not use until it has been inspected.
The best protection against arbon monoxide lnhalation is proper installation
and regular, frequent inspections of thecomplete exhaust system. M you notice a
change in the sound or appearance of exhaust system, shut the unit down
immediately and have it inspected and rewired at once by a competent
mechanic.

EXHAUST MANIFOLD
Two types of exhaust manifolds are used. A dry exhaust
manifold is used on non-marine cooled naturally
aspirated and turbocharged engines. A water cooled
exhaust manifold with integral heat exchanger and
expansion tank is used on marine engines. Exhaust
manifoldsare of a one piece construction manufactured
from alloy cast iron.

FLATWASHER
LOCK TAB

The exhaust manifold is sealed to the exhaust ports with
embossed stainless steel gaskets.

Dry Exhaust Manifold Removal
1. If engine is installed in an application, remove all
components necessary to gain access to exhaust
manifold.
2. Remove exhaust pipe or muffler from exhaust
manifold.

FLANGEHEAD
CAPSCREW

crimp with a pliw to fully
contact a flat or cornef of
the hex.

This edge of lock tab
mutt contact unmachined
ridge left from spolfacing
operation in ordef to
prevent rotation in a CCW
& i o n (loosening)
when installed.

LOCK TAB

3. If engine is equipped with a turbocharger, unbolt
turbocharger from exhaust manifold.

4. Remove capscrews from exhaust manifold and
remove manifold.

Dry Exhaust Manifold Installation
1. Install capscrews with flatwashers and lock tabs
when used onto exhaust manifold.

2. Place new gaskets on capscrews.

3. Mount exhaust manifold and torque capscrews
twice to the proper torque using the torque sequence
in Figure 1. Exhaust manifold capscrews without
locktabs should be retorqued after two hours of
operation. Edge of lock tab (Figure 2) must contact
unmachined ridge that remains after spotfacing
operation. This will prevent capscrew rotation in a
counterclockwise direction (loosening) when locktab is crimped, with a plier, to fully contact a flat or
corner of the hex (Figure 2).

Exhaust Manitold Capscrew Torques
28 Nm (21 Ft.-Lb.)
Capscrew with flatwasher
35 Nm (26 Ft.-Lb.)
Flangehead capscrew

FIGURE 2. LOCK TAB INSTALLATION

1-1

Exhaust pipe or muffler mus
place any strain or pressur
turbocharger flange. Make certain exhaust pi
muffler is adequately supported.

4. Connectexhaust pipe or muffler to exhaust mar

5. Install all components removed in order tc
access to manifold.

Exhaust Manifold Inspection
1. After removal wash and clean exhaust manifo
good solvent.

2. Check manifold for carbon deposits, clea
remove any obstructions found in the manifc
FRONT

FMURE 1. EXHAUST MAwfOU) BOLT TOROWE

3. If manifold is cracked, replace it.
4. If mounting surface of manifold is warped sc
will not seal, the manifold must be machinec
replaced.

5. Inspect and clean mounting surface on c
head and exhaust manifold to make sure it i:
gasket material and other deposits.

Water Cooled Exhaust Manifold
emo oval and Installation

Water Cooled Exhaust Manifold and
Heat Exchanger Disassembly, Inspection

1. Remove all components necessary to gain access

1. Remove exhaust elbow and heat exchanger covers.

to exhaust manifold. Drain captive water system by
removing block drain plugs and drain plugs in front
and rear manifold end caps. Drain sea water system
by removing drain plug from 90' elbow at rear of
heat exchanger cover and by removing hose from
sea water pump. On generator set engines remove
the drain plug from the sea water tube assembly
located at the lower front of the generator set model.

Heat exchanger core can be removed from
assembly without removing manifold end caps.
Loosen manifold end cap retaining screws. This
will free heat exchanger core. Push heat exchanger core out one end.

2. Remove manifold end caps from exhaust manifold
and heat exchanger shell.

2. Remove exhaust muffler from exhaust elbow.
3. Disconnect coolant hoses at exhaust manifold
assembly and heat exchanger.

3. lnspect manifold for carbon deposits, clean and
remove any obstructions found in the manifold.
4. If manifold or end caps are cracked, replace them.

4. Use an overhead hoist or suitable lift to support
exhaust manifold assembly.

5. Remove capscrews from exhaust manifold and
remove manifold assembly.

6. By reversing the removal procedure, install manifold
assembly to engine. Refer to Figure 1 for torque
sequence and proper torque value.

5. If mounting surface of manifold is warped so that it
will not seal, the manifold must be machined flat or
replaced.

6. lnspect and clean mounting surface on cylinder
head and exhaust manifold to make sure it is free of
gasket material and other deposits.
7. lnspect heat exchanger core tubes for deposits.
Flush out any deposits that have accumulated in the
tubes.

Water Cooled Exhaust Manifold and Heat
Exchanger Assembly (Figure 3)
Always use new gaskets and O-rings when assembling
heat exchanger and exhaust manifold.
1. Place one coolant flow tube O-ring in each manifold
end cap.
2. Set manifold front cap gasket on front manifold end
cap. Gasket must line up with passages in exhaust
manifold.
3. Lubricate each end of coolant flow tube with clean
vegetable based oil. lnstall coolant flow tube in Oring in front manifold end cap.
4. Slide exhaust manifold over coolant flow tube onto
front manifold end cap.
5. Secure front manifold end cap to exhaust manifold
with capscrews and flat washers. Torque capscrews
to 35 Nm (26 Ft.-Lb.).
6. lnstall heat exchanger shell gasket in front manifold
end cap. Stand assembly on front manifold end cap.
7. Position heat exchanger shell in front manifold end
cap.

8. Place manifold rear cap gasket on exhaust
manifold over coolant flow tube.
9. Place heat exchanger shell gasket on heat exchanger shell.
10. lnstall rear manifold end cap on exhaust manifold
and heat exchanger shell. Hold end cap in place
with three capscrews and flatwashers.
11. Insert heat exchanger core into heat exchanger
shell. Heat exchanger core is centered and held in
place by heat exchanger covers.
12. Place an O-ring and gasket on each heat exchanger
cover.
13. lnstall heat exchanger covers on manifold end caps.
Torque capscrews to 11 Nm (8 Ft.-Lb.).
14. Place exhaust elbow manifold gasket and exhaust
elbow on rear manifold end cap. Torque capscrews
to 35 Nm (26 Ft.-Lb.).
15. If a remote oil filter is used make certain mounting
bracket is installed before installing manifold
assembly. Apply Loctite 271 to MI2 hex head
capscrew that secures oil filter mounting bracket to
engine.

MANIFOLD END
CAP (REAR)

HEAT W

COVER

I SEAL

HEAT EXCHANGER

COVER

HEAT EXCHANGER

OASK*

12 Electrical System
SUBJECT

PAGE

ELECTRICAL SYSTEM OPERATION
12-1
BATTERIES
12-1
PREHEAT COMPONENTS
12-1
12-1
STARTER
Removal and Installation
12-2
Service
12-2
Disassembly
12-2
Inspection and Testing
12-3
Assembly
12-4
ALTERNATOR
12-6
Removal and Installation
12-6
Service
12-6
OPTIONAL SPEED SENSOR ADJUSTMENT (TACHOMETER) ............ 12-8
ENGINECONTROL .................................................... 12-9
ENGINE WIRING DIAGRAM ........................................... 12-10

ELECTRICAL SYSTEM OPERATION
The electrical system includes starter motor, alternator with voltage regulator, fuel injection pump solenoid, storage battery, and glow plugs.
The charging circuit includes battery, alternator, and
voltage regulator. The wet cell battery is the storage
cell for electrical energy required to start engine. It
must be kept fully charged at all times. Electrical
energy drained from the battery is replaced by the
alternator. A voltage regulator in the circuit prevents
excessive current flow from burning out alternator
and damaging battery.
The starting circuit consists of the electric starting
motor, and solenoid, a storage battery, and start
switch. When start switch is placed in the start position, current flows through the starter solenoid, shifting the drive pinion into mesh with the flywheel ring
gear, closing main contacts in solenoid connecting
battery directly to starter motor. When engine starts
and start switch is released, the solenoid contacts
open, automatically disengaging drive pinion.

BATTERIES
If electrolyte level is low, add distilled water to bring
level of each cell to the bottom of filler neck. Be sure
filler plugs are tight and vents are open.
Do not add water In freezing

[PCAUTION weather unless the engine is to be

run long enough (two or t h m hour$) to assure a thorough mixing of water and electrolyte.

Keep batteries clean by wiping them with a damp
cloth whenever dirt appears excessive.
If corrosion is present around terminal connections,
remove battery cables and wash terminals with an
ammonia solution or a solution consisting of 115
grams of baking soda added to 1 litre of water. Be
sure vent plugs are tight to prevent cleaning solution
from entering cells. After cleaning, flush outside of
the battery, battery compartment, and surrounding
areas with clear water.
Keep battery terminals clean and tight. After making
connections, coat terminals with a light application of
petroleum jelly or nonconductive grease to retard
corrosion.
Maintain battery .ina fully charged condition. Check
charge condition or specific gravity with a hydrometer when electrolyte temperature is at 27" C (80"F).

Hydrometer Indication
1.110 to 1.135
1.170 to 1.200
1.205 to 1.230
1.235 to 1.260
1.265 to 1.290

Charge Condition
Completely discharged
One-fourth charged
One-half charged
Three-fourths charged
Fully charged

When batteries are being charged, an explosive gas
forms under each cell cover. Some of this gas
escapes through vent holes in the plugs. This gas
may form an explosive atmosphere around the battery if ventilation is poor.
Explosive gas may remain in and
1after
AWA'N'NG~ around the battery for seven/ hours
it has been charged. Sparks, flames, or smoking
can ignite this gas causing an explosion which could
shatter the battery. Hying pieces of the battery structure and splash of electrolyte can cause personal
iniury.

PREHEAT CIRCUIT COMPONENTS
The preheat system consists of glow plugs, glow plug
control, and a switch to energize preheat circuit. The
glow plugs supply heat to the cylinders so compression temperatures are high enough to ignite the fuel
during start-up.
Before testing, remove wires from all glow plug
terminals. Then, test each glow plug individually for
continuity (a high resistance). A plug that tests
"open" must be replaced.

STARTER (Mitsubishi)
The standard starter motor is a 12 volt, overrunning
clutch type, with an integral solenoid. The solenoid is
connected by a lever assembly to a clutch in the front
bracket (nose) assembly. Thesolenoid shifts the pinion gear into mesh with flywheel ring gear and holds it
in place during engine cranking.
DO not 0-0
star& fpr periods
longer than dO,.se.qonds without
allowing 2 minutes for starter to cool. Failure to
obaewe this caution can result in overheating and
hilure of the motor.

FIBER
WASHERS

SOLENOlD

TERMINAL "M"

ARMATURE

STOPPER
(RETAINING
RING)

ADJUSTMENT
SPRING

OVERRUNNING
CLUTCH

WASHER

ASSEMBLY

FIGURE 1. STARTER MOTOR

Service
When starting engine, note starter motor action. The
pinion gear should mesh quickly with flywheel ring
gear and spin engine. Onceengine starts and solenoid
opens, the starter should disengage and stop. If
starter cranks engine slow or not at all, check start
circuit components. Failure to crank is normally
caused by low battery charge, defective battery
cables, corroded or poor connections, or low temperatures. If after checking these variables, starter
continues to crank slow it must be removed and
repaired.

Disassembly
1. Remove "M" terminal nut and wire lead from
solenoid (Figure 1).

2. Remove the two solenoid mounting screws and
remove solenoid.
3. Remove the two through bolts and brush holder
retaining screws. Remove rear bracket (Figure 2).

Removal and Installation
1. Remove both battery cables from battery. Dis-

3.
4.

connect ground cable first.
Disconnect battery cable and electrical lead wires
from starter.
Remove capscrews and flat washers that attach
starter to flywheel housing.
Remove starter. Some rotation of starter may be
necessary in order to clear flywheel housing.
Mount starter motor to engine by a direct reversal
of the removal procedure. Connect battery cable
and wires to starter.
~ i n ' n e c tbattery cables to battefy. Connect
giound cabie last.

9
FIGURE 2 REMOVING REAR BRACKET

Es11W

4. Remove frame assembly and brush holder assem-

Inspection and Testing

bly1 while pulling the brushes upward. Then
remove armature assembly.
5. Remove cover assembly. (snap ring and washer)
from the pinion shaft (Figure 3).

Inspect the starter components for mechanical defects before testing for grounds or shorts.
Testlng Armature for Ground8:Touch armature shaft
or core and each commutator bar with a pair of
ohmmeter leads. If ohmmeter or continuity tester
shows continuity, it indicates a grounded armature.
Replace the armature assembly. See Figure 5.

COVER

WASHER-

&
.

SNAP RING

FIGURE 3. REMOVING SNAP RlNG AND WASHER

6. Remove capscrew that secures center bracket to
front bracket. Remove the center bracket; several
washers used to adjust pinion shaft end play can
now be removed (Figure 4).
FIGURE 5. TESTING ARMATURE FOR GROUNDS
FRONT

CAPSCREW

p
d

Testing Armature for a Short Circuit: Use a growler
for locating shorts in armature. Place armature in
growler and hold a thin steel blade (e.g. hacksaw
blade) parallel to the core and just above it while
slowly rotating armature in growler. A shorted armature will cause the blade to vibrate and be attracted to
the core. If armature is shorted, replace with a new
one (Figure 6).
ADJUSTMENT
WASHERS

-HACKSAW
BLADE

FIGURE 4. REMOVING CENTER BRACKET
GROWLER

7. Removegear, spring set, and lever assembly from
front bracket. Note direction in which the lever
assembly is installed.
8. Push pinion gear and stopper down and remove
retaining ring. Remove stopper, pinion gear,
spring, and pinion shaft assembly.
9. Inspect ball bearings. If they are rough or noisy
when rotated replace them. The front bearing is
not replaceable and must be replaced with the
bracket.

ES-1189

FIGURE 6. TESTING ARMATURE FOR SHORT CIRCUITS

Inspecting tor an Open Clrcult In Armature: Using an
ohmmeter, check for continuity between thecommutator segments. If there is no continuity (high resistance), the segments are open and armature must be
replaced (Figure 7).

Check for shorts between positive side of brush
holder and brush holder base. If there is continuity,
replace holder assembly. Check for free movement of
brushes. All brushes should move freely in the brush
holders.

Soknold: Push solenoid plunger in and release it.
The plunger should return to its original position.
While holding plunger all the way in, check for
continuity between terminals "M" and "6". If there is
no continuity, replace the solenoid (Figure 9).

COMMUTATOR

TERMINAL

ES11U

FIGURE 7. TESTlNG ARMATURE FOR OPEN CIRCUITS

Commutator Inspection: If commutator is dirty or
discolored, clean with number 00 to 000 commutator
paper. Blow grit out of armature after cleaning.
If commutator is scored, rough or worn, turn it down
in a lathe.

Held Coll: Use an ohmmeter to check for continuity
between brushes. If there is no continuity, the field
coil is open and must be replaced. With field coil
mounted in the frame, check for continuity between
the field coil and frame. Replace frame assembly if
there is continuity.
Brushes: Clean around brushes and holders wiping
off all brush dust and dirt. If brushes are worn shorter
than 11.5 mm (.4528 inch) replace them (Figure 8).

FIGURE 9. SOLENOID TERMINALS

Reductton G m n : Inspectarmature shaft gear, reduction gear, and pinion shaft gear for wear and damage.
Replace any part that is worn or damaged.
Overfunlng Clutch: Inspect pinion and spline teeth
for wear or damage.
If pinion gear is worn or damaged inspect flywheel
ring gear also. Rotate pinion. It should turn free when
turned in one direction, and lock when turned in the
opposite direction.
Do not clean ovemnnlng clutch In
solvent or liquld cleanlng solution.
Washlng the clutch wlll a w e the g m 8 e to Imk out.

$r,wm$
Starter Assembly

LIMIT

U-11~

FIGURE 8. BRUSHWEAR UMIT

For assembly reverse the disassembly procedure, but
note the following items.
Lubdutbn: Whenever starter motor is disassembled
apply grease toeedh of the following points. (Recommended grade; Multemp PS No. 2.)
Armature shaft gear
Reduction gear
Ball bearing (Both ends of armature)
Stopper on pinion shaft
Sleeve bearing
Pinion gear
Sliding portion of lever

pinion Shaff End Play Adjustment: Adjust end play so
that it is 0.1 to 0.8 mm (.0039 to .0315 inch) with the
adjusting washers placed between center bracket
and reduction gear (Figure 10).

OVERRUNNING

PINION SHAFT

SNAP RING

FIGURE 11. PINION GEAR INSTALLATION

REDUCTION GEAR

ADJUSTING WASHER

WASHER

CENTER
BRACKET

LeverAssembiy installation: Figure 12 shows the correct method of installing the lever assembly, spring,
and packing. Pay close attention to direction of lever.

FIGURE 10. ADJUSTING PINION SHAFT END P U Y

FRONT
BRACKET

With pinion gear removed, install reduction gear onto
pinion shaft. Place pinion shaft into center bracket
and secure with washer and snap ring. Measure the
end play with a feeler gauge between center bracket
and gear. If necessary, adjust end play by adding or
removing adjusting washers.
If pinion gear has not been removed, place pinion
shaft and reduction gear between front bracket and
center bracket. With lever spring removed and bolt
tightened, push pinion shaft out and measure end
play. Adjust end play if necessary by adding or
removing shims.
Pinion Gear lnrlallatlon: Placespring and pinion gear
onto pinion shaft. Slide stop ring onto pinion shaft
and install retaining ring in groove. Pull stop ring over
retaining ring (Figure 11).

LEVER

CENTER
BRACUE1

LEVER
SPRING

FIGURE 12 LEVER tNSTALLATlON

Pinion Gap Adjustment: After assembling starter
motor, adjust pinion gap.
1. Remove "M" terminal nut and wire from solenoid.

2. Connect positive terminal of battery to "S" terminal on solenoid and negative terminal to starter
body. With battery connected pinion gear will
shift into the cranking position.
3. Gently push pinion shaft back towards front
bracket and measure the amount of travel (Figure
13).

PINION

AMOUNT

'TRAVEL
I

f+i

-a(PINION GAP)

FIGURE 13. PINION GAP ADJUSTMENT

4. The pinion gap should be 0.3 to 2.0 mm (.0118 to

.0787 inch). Adjust by changing the number of
fiber washers used on solenoid mounting surface. Increasing the number of fiber washers
decreases clearance. Decreasing the number of
washers increases clearance.

ALTERNATOR
The alternator is a continuous output, diode rectified
unit, designed and constructedto provide long periods
of dependable service with minimum maintenance.
The alternator assembly consists of an alternator and
voltage regulator combined as a single unit. Two
brushes carry current through two slip rings to the
rotor field coil. The rotor is mounted on sealed ball
bearings eliminating the need for periodic lubrication.
The stator windings are a part of the laminated core
that forms a portion of the alternator housing.
Mounted in the rear housing are six rectifier diodes
that are connected to the stator windings. The six
rectifying diodes changealternating current and voltage to direct current and voltage, by a three-phase,
full wave rectifier system.
It is not necessary to remove alternator to replace the
brushes or voltage regulator. These operations are
usually done with alternator on engine.
The following information is for field use only. For a
major repair, remove alternator and take it to a reputable alternator repair shop.

Removal and Installation
1. Remove capscrew attaching alternator to adjusting bracket and loosen capscrew that secures
alternator to bracket.
2. Remove drive belts from alternator pulley.
3. Mark alternator lead wires for subsequent installation. Disconnect lead wires.
4. Remove capscrew attaching alternator to mounting bracket. Note location of spacer and remove
alternator.
5. Install alternator by reversing removal procedure.
6. Adjust belt tension. Refer to SECTION 9, COOLING SYSTEM Drive Belt Adjustment procedure.

Service
If alternator output is weak check the following items
before removing alternator for servicing.
1. Check drive belts for alignment, tension, and

wear.
2. Check for loose alternator drive pulley and loose
alternator mounting.
3. Check terminalsfor corrosion and loose connections. Check wiring for frayed insulation and
breaks.
4. Remove and inspect brush assembly.

5. Alternator Output Test
Use a DC voltmeter (0-30 volts) to measure
alternator output. Connect the negative lead from
the voltmeter to a good ground on the alternator.
Connect the positive lead from the voltmeter to
the positive output terminal on the alternator
(Figure 14).
With voltmeter connected, start and run engine at
a fast idle of approximately 1000 rpm. A charging
system operating properly has a normal system
output voltage between 13.8-14.8 volts.
If thealternator output voltage does not fall within
the proper range, remove thealternator for further
inspection and testing.

GND
(NEG)

FRAME (NEGATIVE)

FIGURE 14. ALTERNATOR OUTPUT TEST CIRCUIT

VOLTAGE REGULATOR
MOUNTS HERE

Brush Awembly Removal:
1. Removevoltage regulator. Make certain regulator

leads are disconnected from studs on rectifier
diode plate. Remove three screws which fasten
regulator and hold regulator away from rear
housing. Detach regulator brush connecting lead.
2. Remove two brush mounting screws from cover,
and lift cover and dust shield from brush.
3. Remove brush assembly by pulling up and outward to clear index pins.
4. Assemble brush assembly by reversing disassembly procedure (Figure 15).

ASSEMBLY

8..--*32
SCREWS
ES-ll(0

FIGURE 15. MOTOROLA ALTERNATOR

Brush Assembly Inspection:
1. Measure brush length. Replace, if less than
4.2 mm (0.1654 inch) extends below bottom of
holder.
2. Clean entire holder assembly in cleaning solvent

and dry. Check movementof brush in holder, asa
binding condition will result in poor slip ring
contact.
3. Check brush spring tension. A brush spring
tension of 113 to 170 grams (4 to 6 ounces) is
required to move brush against spring.
4. Check surface of slip rings. If surface is smooth
but covered with a carbon-oil-dirt mixture clean
with fine crocus cloth and wipe dust and residue
away. If slip rings are rough or out-of-round,
replace the rotor assembly.

OPTIONAL SPEED SENSOR
ADJUSTMENT (Tachometer)
Adjust magnetic pick-up sensor, located on the
flywheel housing (Figure 16) as follows:
Dlrconnect engine batteries. D k -

AWARN'NG connect engine from load. Acciden-

tal starting of unit can result In serioua personal
injury.

I. Remove sensor.
2. Manually rotate ring gear so one gear tooth is
centered directly under sensor mounting hole.
3. Install sensor by turning inward until pole face
just touches the gear tooth.
4. Back sensor out 3/4 turn and tighten "jam nut"
(Figure 16). [The gap between the sensor and the
gear tooth should be 0.9 to 1.3 mm (0.035 to 0.050
inch).]

SENSOR INSTALLATION

~~~~~~
I?

1. Connect an ohmmeter or test lamp (12 volts) to
the field terminal and to the bracket. The test
lamp should not light or resistancereading should
be high (infinite). If not, there is a short and the
assembly must be replaced.

2. Move one ohmmeter lead from the bracket to
insulated brush. Use an alligator clip directly on
the brush. Be careful not to chip it. Resistance
reading should be zero (continuity).
3. Connect ohmmeter leads to the grounded brush
and the bracket. Resistance should be zero
(continuity).

I
RING GEAR

--I-I

GAP
0.9 TO 1.3 MM
(.035 to ,050 INCH)

SC-1262

FIGURE 16. SPEED SENSOR ADJUSTMENT

ENGINE CONTROL
Due to the widevarietyof uses to which theseengines
are adapted, operating controlsare not supplied with
the engines. In most cases, the engines are used for
prime power to operate other manufacturers' equipment. Installation nearty always differs, and the
manufacturer or fabricator generally provides a control
for the complete unit.
Purpose of the control is to tie the starting and
charging circuits together at a convenient location.
The control may also contain gauges to monitor
engine operationand emergency shut-down funtions.

Maintenance
Periodically check all connections and contacts in
the control system to be sure that they are tight and
clean.

ON Pressure Gauge: lndicates pressureof lubricating
oil in main oil gallery when engine is running.
Start-Stop Swltch: When in the start position, this
switch connects battery power to the start solenoid
for engine cranking. The. switch also controls the
power to the fuel injection pumpsolenoid and returns
to the run position when it is released.
Ammetec lndicates battery charge condition.
Preheat Swltch: The preheat switch is a momentary
ON switch that cotnrols power to the glow plugs for
cold engine starting.
Preheat Lamp: The preheat lamp is lit during preheating. The lamp will go out when the engine is
ready for starting.
Fuse: The fuse protects the starting and charging
circuitsfrom burning out if a short should occur in the
circuit.

Standard Control

Preheat Circuit

Only the standard control used on the closed L Series
Power Units is covered in this section. The control is
located on the rear housing. This control has a
coolant temperature gauge, oil pressure gauge,
ammeter, preheat switch, preheat light, start-stop
switch, and a fuse to protect thecircuit on the control
panel (Figure 17).
Coolant Temperature Gauge: Indicates temperature
of coolant in engine water jacket.

The preheat circuit consists of glow plugs, ballast
resistor, and a switch toenergize preheat circuit. The
glow plugs supply heat to the cylinders permitting
compression temperatures to ignite the fuel during
start-up.
Using an ohmmeter, check glow plugs and ballast
resistor for continuity. If there is no continuity (high
resistance), the components are open and must be
replaced.

OIL PRESSURE
GAUGE
\

AMMETER

PREHEAT SWlTCH

COOLANT
TEMPERATURE
GAUGE

PREHEAT LAMP
START-STOP
SWITCH

FIGURE 17. CLOSED POWER UNIT CONTROL ( W C A)

FUSE

WIRING DIAGRAMS
Wiring Diagram for Electronic Control Unit (ECU)

ECU Part
No. 333-0237

men u m m indiate AWG sin.If wim ienm mllSt e

M-1505-1

x d 3m (10 fwt)*

use next hrgar wire Site.

ECU Part
No. 333-0231

un-~~*ro~wh~u*rrrrm(le*.l).
ucunext~*"=.
REF.
ST1
01
ECU
Fl
F2
01
HRl-6

DESCRlPflON
B.W,1ZV
Start.r, Sohnoid
Ekctrocrk Contrd UnH
Fuse (50 amp, 3 6 4 cyl.; 80 amp, 6 cyl.)
Fucu(2Ormp)
Al-Of
6 ROSUMW
Glow P ~ w
F u l ln(rtlonPump Solodd ( W k Ground b I n U )

S2 and 53 are often combined in an automotive type key switch.
i

,.~

REF.
L1

M2
p

OESCRlmON
Limp, GiOW mug

~chrrg.lndlcrtor(Oo11orul)

~(001knrl)
V-(Om)

Hounn-(Optknrl)

w,F u l W k d d (nWMw 0P.n.SMP m

Wiring Diagram for Ballast Resistor Control Unit
R1

BATTERY

SOLENOID
K3

ST1

Large numben indicate AWG slze. If w i n length must exceed 3m (10 feet),
use next larger wire size.
REF.
BT1
B1
F1
F2
GI
HR1-6
J1
K3
L1
L2

DESCRIPTION
Battery, l2V
Starter, Solenoid
Fuse (50 amp, 3 & 4 cyl.; 80 amp, 6 cyl.)
Fuse (20 amp)
Alternator & Regulator
Glow Plug
Connector
Fuel Injection Pump Solenoid
Lamp, Glow Plug
Lamp, Charge Indicator (Optlonal)

- S2 and S3 are often combined in an automotive type key switch.

REF.
M1
M2
M3
R1
S1

DESCRIPTION
Ammeter (Optional)
Voltmeter (O~tional)
ourm meter (0~tlona1)
Resistor, Ballast
Switch, Glow Plug (normally open,
momentary contact)
Switch, Fuel Solenoid (normally open,
snap action)'
Switch, Start (normally open,
momentary contact)'

13 Engine Disassembly
SUBJECT

PAGE

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ENGINE REBUILDING RECOMMENDATIONS
13-1
Disassembly
13-1
Assembly
13-1
Break-in Procedure
13-2
CYLINDER HEAD
13-3
Removal
13-3
Inspection
13-4
Refacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4
......
Hotplugs
13-5
Installation
13-6
VALVELASHADJUSTMENT
13-8
VALVES
13-10
Removal
13-10
Inspection and Repair
13-10
Assembly
13-13
VALVE FACE AND SEAT GRINDING
13-14
CRANKSHAFT PULLEY AND DAMPER
13-17
Pulley Removal
13-17
Pulley Installation
13-17
FLYWHEEL AND RING GEAR
13-18
Flywheel Removal
13-18
Flywheel Inspection
13-18
Ring Gear Inspection. Removal. and Installation
13-18
Flywheel Installation
13-18
FLYWHEEL HOUSING
13-19
Removal. Inspection. and Installation
13-19
CRANKSHAFT REAR OIL SEAL AND WEAR SLEEVE
13-20
SealRemoval
13-20
Wear Sleeve Removal and Installation
13-20
Seal Installation
13-20
CONNECTING ROD AND PISTON ASSEMBLY
13-22
Removal and Disassembly
13-22
Piston Inspection
13-23
Connecting Rod Inspection
13-24
Connecting Rod Bushing Replacement
13-25
Connecting Rod to Piston Assembly
13-25
Piston Assembly Installation
13-27

PAGE

rBLY ....................................... 13-28
............................................ 13-28
.............................................. 13-28
.r ............................................. 13-29
;arings .......................................... 13-29
................................................. 13-30
.................................................. 13-31
................................................... 13-31
Insk .ion Solid Tappets ...................................... 13-31
HydraulicTappets ........................................... 13-31
Installation ................................................ 13-31
GEARCASE COVER .......................................... 13-32
Removal .................................................. 13-32
Installation ................................................ 13-32
CRANKSHAFT FRONT OIL SEAL AND WEAR SLEEVE ............... 13-33
Seal Removal .............................................. 13-33
Wear Sleeve Removal and Installation ........................... 13-33
Seal Installation ............................................ 13-33
GEARCASE AND BACKPLATE .................................. 13-34
Idler Gear and Shaft ......................................... 13-34
Backplate ................................................. 13-34
CRANKSHAFT ...............................................13-36
Removal .................................................. 13-36
Inspection and Repair ........................................ 13-36

................................................13-36
......................................... 13-38
.............................................13-39
.................................................. 13-39
................................................. 13-39
................................................ 13-39
.......................... 13-39
...................... 13-40

Installation
CRANKSHAFT GEAR
MAIN BEARINGS
Removal
Inspection
Installation
Replacement with Crankshaft Installed
Checking Bearing Clearance with Plastigage
CYLINDER BLOCK
Cleaning
Inspection
Reboring the Cylinder
Honing Cylinders
Oeglazing Cylinder Bores

........................................... 13-41
.................................................. 13-41
................................................. 13-41
....................................... 13-42
........................................... 13-42
..................................... 13-43

ENGINE REBUILDING
RECOMMENDATIONS
Removal and installation of enginecomponents such
as cylinder head, pistons, crankshaft, camshaft, etc.,
are covered in this section. The extent of the work to
be done on engine determines which accessories
such as starter, alternator, water pump, fuel pump,
etc., must be removed. When completely overhauling
an engine, all accessories should be removed, disassembled, inspected, and repaired or replaced as
required before they are reinstalled on engine.
Have an adequate supply of pans or boxes available
for storage of small parts and hardware as they are
removed. Machined parts that have surfaces which
could be damaged should be stored on wooden racks
or supported on wooden blocks. Mark all parts that
are identical, such as valves, rocker arms, push rods,
tappets, etc., and store in racks so they can be reinstalled in their original position.
The disassembly procedures outlined in this section were done
with the engine mounted on an engine stand unless otherwise
noted. Right side and lefl side is determined by facing flywheel end
(rear) of engine.

Use an engine stand whenever extensive repair or a
complete engine overhaul is required, Before engine
can be attached to the stand, remove exhaust manifold, oil cooler, and any optional equipment that is
attached to left side of engine. There are four 12mm x
1.75 threaded holes located on left side of engine.
Mount engine to stand using these four threaded
holes. An adapter plate may be necessary depending
on the type of engine stand being used.
Use of the special Onan service tools illustrated in
this manual is recommended. Most jobs can be
accomplished faster and more accurately when the
proper tools are used. Many items require a special
tool for correct removal and installation. Some of the
recommended tools are:
Front and rear oil seal tools.
Valve spring compressor, valve guide driver, and
valve seat remover.
Gear puller and gear puller rings.
Piston ring spreader and compressor.
Cam bearing puller.
Torque wrench, plastigauge (for correct bearing
clearance).
Front and rear (seal) wear sleeve installation tool.
See Onan Tool Catalog (900-0019) and SECTION 4,
SPECIAL TOOLS of this manual for specific tool
numbers.

Disassembly
The order in which engine components are removed
is left to the discretion of the mechanic. As disassembly progresses, the order may have to be changed to
suit the application. A suggested disassembly procedure would be as follows:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.

Tag and identify all wires removed.
Drain coolant.
Drain oil discard oil removed.
Fan, water pump, alternator.
Fuel lines, transfer pump, injection pump.
Fuel filter, oil filter.
Oil pan, oil pick up tube.
Flywheel, flywheel housing with starter.
Rear seal plate assembly.
Rocker cover, cylinder head, tappets.
Gearcase cover, camshaft, gear train.
Gearcase backplate with oil pump, oil pressure
regulating valve.
13. Piston and connecting rod assemblies.
14. Crankshaft and main bearings.
15. Cam bearings.

Analyze the remons for any component's failure and extent of the
repair required. Determine if cylinder bores require reboring.
cnnkshaft journals needgrfnding. or ifother machine shop work is
necerury. All machining work must be performedby a qualified
machine shop. Replace all worn or damaged parts with new parts.

Assembly (Use Genuine Onan Parts)
NEAT, CLEAN, AND ORDERLY WORK AREAS MAKE THE JOB
EASIER.

1. Engine assembly procedure is normally the
reverse of disassembly. Observe proper clearances of bearings, connecting rod, proper fitting
and sizing of piston, rings, etc. A list of dimensions and clearances is furnished in SECTION 2,
DIMENSIONS AND CLEARANCES of this
manual.
2. Follow the recommended procedure for the fitting of valves, pistons, bearings, and adjusting
clearances.
3. A torque wrench is a must when assembling
engine. All torques specified are wet. Use clean
engine oil to lubricate threads prior to installation. A table of torques is furnished in SECTION
3, ASSEMBLY TORQUES of this manual and
should be used whenever capscrews or nuts are
tightened.

4. Use new gaskets whenever required. A new
cylinder head gasket must be used each time
cylinder head is removed.
5. Use capscrews of the correct size, type, grade,
and length. Size and length of various capscrews
are listed in the Parts Catalog available from your
dealer. Hardened flat washers must be used
wherever indicated. Lockwashers are not recommended and should not be used anywhere
on theengine. Always tighten each fastener to its
recommended torque.
6. As each internal engine part is assembled, manually rotate crankshaft, making ce*in it turns
freely. If tightness is noted after any operation
you then know your last step is the cause.
7. As each internal engine part is assembled, coat it
heavily with oil (same grade used in crankcase).
During the first few critical moments of operation,
the engine will depend on this oil for lubrication.
8. After you have the internal engine parts reassembled, the engine should turn freely. If care
and attention have been given, engine will operate efficiently.
9. Refer to Cylinder Head and Valve Lash Adjustment
for cylinder head capscrew torque sequence and
for valve lash adjustment.
10. For correct injection pump timing see SECTION
10, FUEL SYSTEM.
11. At this point, it is a matter of mechanically adding
outside accessory items to the block assembly.
Order of assembly is reverse of disassembly.

12. When engine is complete, install controls. Reinstall the tagged wires. Use wiring diagram to
connect leads to control, and from control to
engine. All wires should have been marked for
correct identification. If unit is to work properly,
wires must be connected correctly.
13. Follow set-up and starting procedures outlined in
SECTION 6,START-UP of this manual.
14. Start engine and check for oil pressure buildup.
15. Check for oil, fuel, and exhaust leaks. Correct any
leaks found.
16. Run engine about 15 minutes under light load to
reach operating temperature.

Break-in Procedure
The only time an engine will require a break-in
period, is when the pistons are removed or after
cylinder boring. The unit should be run in the
following sequence.
1. One half hour at 1 / 2 rated speed with one quarter
load applied.
2. One half hour at rated speed with one half load
applied.
3. Full rated speed under normal operating
conditions.
Drain and replace crankcase oil and filter after the
first 50 hours of operation: drain while engine oil is
still warm.
When overhauling a turbocharged engine head bolts
must be retorqued,after runningfor two hours with load.

CYLINDER HEAD The cylinder head is made from high strength cast
iron alloy. It is secured to cylinder block by hardened
capscrews. Intake and exhaust ports are cast in the
cylinder head for the intake of air and the expulsion of
exhaust gases. Cored passages are provided for the
circulation of coolant in the head. A gasket is used to
seal combustion chamber and all water and oil passages between the block and head. The flow and
distribution of coolant through head is controlled by
various size coolant flow holes in head gasket.
Located in cylinder head above each cylinder is an
intake and exhaust valve, valve springs, guides.
spring retainers and locks, a fuel injection nozzle,
glow plug, and two rocker arms. The valve train is
enclosed within a rocker arm cover and sealed with a
gasket.
Service on some parts of cylinder head can be done
with the head installed on engine. For other service
the head must be removed from cylinder block.

Service Operations That Do Not Require Removal
of Cylinder Head Are:
1. Valve lash adjustment.
2. Servicing or replacement of fuel injection nozzles.
3. Replacement of rocker arms, rocker arm studs, or
push rods.

Service Operations That Do Require Removal of
Cylinder Head Are:
1. Replacement or grinding of the valves.
2. Replacement of valve guides.
3. Grinding or replacement of valve seats or inserts.

Cylinder Head Removal
1. Drain cooling system. Refer to SECTION 9,

COOLING SYSTEM.

2. Remove or disconnect all components and
assemblies necessary to gain access to cylinder
head, such as exhaust pipe, engine shroud, air
cleaner, etc.
3. If engine is equipped with a turbocharger, disconnect turbo oil lines and remove turbocharger
assembly.
4. Remove fan belt, fan, and water pump assembly.
5. Disconnect fuel lines from injection nozzles and
injection pump. Remove fuel return lines from
injection nozzlesand injection pump. Cap all fuel
line openings to prevent the entrance of dirt or
dust.

Due to the precke tolerancesof
diesel lniectlon systems, It is
extremely Important the fuel be kept clean. Did in
system can cause severe damage to both iniecHon pump and ln/ectlon nozzles.

6. Remove injection lines.
7. Remove capscrews and washers that secure
intake and exhaust manifolds to head.
8. Remove manifolds, gently tap with a soft hammer,
if necessary.
9. Remove lead from glow plugs.
10. Remove rocker arm cover.
11. Disconnect rocker arm oiling tube from the pipe
fitting at front of engine and remove oiling tube.
12. Remove rocker arms, push rods, and valve stem
caps.

Keep rocker arms, rocker 8rm balls, washers, rocker arm nuts,

and pushrod$in order, so they go back in the same valve train
porltlon.

13. Remove capscrews securing cylinder head to
block.
14. Remove head by lifting it straight up until the
dowel pins in block are cleared.
15. Remove head gasket.

Cylinder Head Inspection
Visually check for damage to the sealing surfaces of
cylinder head and block. Clean all carbon deposits
from head by scraping or brushing with a wire brush.
I f engine has overheated or has compression leaks,
check head for warpage and cracks. Use a heavy,
accurate straight edge and feeler gauge to check for
warpage (Figure 1) at each end and between all
cylinders. Check cylinder head for end-to-end warpage in at least five places.

FEELER
GAUGE

STRAIGHT EDGE

2. Grinding
A. Inspect the hot plugs and replace any that are
worn or damaged.
6. Make certain that all hot plugs are tight in the
counterbores. Use Locktite 325 to secure any
loose hot plugs;
C. Reface the cylinder head by grinding.

After refacing the cylinder head the valves and seats
must be ground. Refer to Valve Face and Seat Grinding procedures.

BRASS
ORlFT

FIGURE 1. CHECKING THE HEAD FOR WARPAGE

Cylinder Head Refacing
If cylinder head face is scratched, nicked, or warped it
may be refaced. A maximum of .25mm (.0098 inch)
can be removed from face of head before it must be
replaced.
FIGURE 2 HOT PLUG REMOVAL

The cylinder head surface may be refaced by either
one of the following methods:
1. Milling:

A. Remove hot plugs and inspect. Remove hot
plugs by placing a brass drift into injection
nozzle bore and driving out the hot plug (Figure 2). Reface cylinder head on a milling
machine.

6. Grind hot plugs individually making certain
the hot plug face does not protrude more than
.065 mm (.0026inch) or recess more than .025
mm (.001 inch) from cylinder head gasket
surface.
C. Install hot plugs. See Hot Plugs for correct
installation procedure.

Hot Plug
GUIDE

Hot plug throat size varies depending on engine
operating speed and application.
If hot plugs are damaged or show signs of erosion,
replace them. After a short period of running, hot
plugs will develop hairline cracks. This is normal and
acceptable.
Clean hot plugs to remove any carbon deposits and
inspect. Replace hot plug if any hairline cracks intersect, or a piece of the hot plug has broken out. Clean
carbon deposits from hot plug counterbore with a
wire brush after removing injection nozzles.
When installing hot plugs, note the keyway in head
and the raised guide on hot plug (Figure 3). Align
guide on hot plug with keyway in head and drive hot
plug in with a soft hammer.
The hot plug face must not protrude more than
0.065 mm (0.0026 inch) from cylinder head gasket
surface. If protrusion of hot plug is greater than
specified, remove hot plug and grind face of plug.
The hot plug face must not be recessed more than
0.025 mm (0.001 inch). If recess is greater than
specified, replace hot plug.
If hot plug is loose in counterbore after installation,
remove hot plug and coat it with Locktite 325 before
reinstalling. This will keep hot plugs in place while
assembling head to block.

FIGURE 3. HOT PLUG INSTALLATION

Cylinder Head Installation
Make certain machined surfaces of cylinder head and
block are thoroughly clean. A new head gasket must
be installed before installing cylinder head.
Before cylinder head h Inslalled,
make certain that there k not an
excessive amount of oil, or any other Ilquld, In the
capscrew hoks In cyllnder block. Toomuch 011 In any
of these holes may cause a hydroststlc lock when the
capcrew k tightened.

iAcnuTioN

1. Check for warpage, scratches or nicks on sealing
surfaces of head and block. Repair or replace the
head if necessary.
2. Clean cylinder block and head contact surfaces.
Thoroughly clean cylinder bores of any foreign
material or liquid. Install valve tappets.
3. Install a new cylinder head gasket over dowel
pins and on to cylinder block with the indicated
side up as marked on gasket. Do not use any
sealer or gasket cement. The gasket is precoated
with a sealer and anti-stick compound.
4. Position cylinder head assembly gently over
dowel pins and onto cylinder block.
5. Lubricate cylinder head capscrew threads with a
light coat of clean engine lubricating oil.

6. Install head bolts, washers, and push rods with push
rod guides. There are no flat washers on the bolts
for the push rod guides. Draw cylinder head down in
gradual and even steps to assure a good seal
between cylinder head and block. Tightening the
head bolts in one step may distort head and cause
head gasket leakage. Tighten each bolt about 1/ 4
turn at a time until the specified torque of 129 Nm
(95 Ft.-Lb.) is reached. Figure 4 shows the torque
sequence for tightening cylinder heads.
When overhauling a turbocharged engine head
bolts must be retorqued, after runningfor two hours
with load.
7. Make certain push rods are seated properly in
tappets.

8. Position rocker arms. rocker arm balls, and flat
washers on the same rocker arm studs that they
were removed from.

9. Lubricate threads on rocker arm studs and install
rocker arm locknuts. Lubricate rocker arm assemblies with clean SAE 10 engine oil.
Replace any rocker arm locknut that cannot hold a
minimum wet torque of 3.4 Nm (30 In.-Lb.). New,
well oiled rocker arm locknuts should have a
minimum initial torque of 6.2 Nm (55 In.-Lb.).

4.nd6Cytlndrr

FIGURE 4. CYUNOER H U D BOLT TOROOL SEQUENCE

Do not tlghhn rockerarm locknuts. Pulllng locknuts down
tlght will cause valves to hltplstons when making
valve clearance adjustment. Do not run the
rocker arm nuts down with an air wrench. Using
an air wrench to remove or install locknuts wlll
destroy the self-locking feature.

11. lnstall rocker arm oiling tube on Spec A to C

10. Set valve clearance. Refer to Valve Lash Adjustment
procedure.

13. Place new injection nozzle seals in nozzle bore
with the concave side down (Figure 5). Do not

engines. Make certain rocker arms clear oiling tube,
as engine crankshaft is rotated one complete
revolution.
12. lnstall rocker arm cover with a new cover gasket
and capnut gaskets.

reuse injection nozzle seals. They must be
replaced whenever nozzles are removed. lnstall
injection nozzles into cylinder head and tighten
to the specified torque.

N O U L E SEAL

- lei

Incorrect lnstallat~nof lniectlon nozzle seals wlll cause
Injection nozzle to overheat and stick. Stlcky
nozzles cause excessive nolse and smoke.

'7.-

. _ ----

@'I
.

- -__-.

14. lnstall and connect glow plugs and leads.

FIGURE 5. INJECTION NOULE SEALS

15. Mount intake and exhaust manifolds.
16. lnstall and connect fuel lines. Make certain the
lines are clean and dry before installing them.
17. Grease "0"ring on cylinder head water outlet
with a light duty grease. Replace "0"ring if any
nicks or cracks are evident.
18. lnstall water pump, water pump pulley, and fan
belt. Refer to SECTION 9, COOLING SYSTEM.
19. Complete remainder of installation by a direct
reversal of disassembly procedure.
20. Refill cooling system with clean coolant. Refer to
SECTION 7, MAINTENANCE.
21. Inspect engine for fuel, coolant, or oil leaks and
correct any leaks found.
,

VALVE LASH ADJUSTMENTS
Valve adjustment is achieved by turning rocker arm nut
up or down until correct valve lash is obtained between
valve stem and rocker arm. Allow engine to cool before
adjusting. The cylinders are numbered from front to
rear.
To adjust valve'lash, proceed as follows:

With the piston at TDC the crankshaftcan be turned
90' in either direction without the valves on number
one cylinder opening. If the valves open during this
test the crankshaft must be turned one complete
revolution (360') in the direction of normal rotation.

Solid Tappet Valve Lash Adjustment (Spec A to C)

1. Place start-stop switch in stop position to prevent
accidental starting.

See SECTION 1, SPECIFICATIONS for correct valve
lash.

2. Removeall parts necessary to gain access to rocker
arm cover.

1. To check valve lash, insert the correct size feeler

3. Remove rocker arm cover.

4. Replace any rocker arm locknut that cannot hold a
minimum wet torque of 3.4 Nm (30 In.-Lb.). New,
well oiled rocker arm locknuts should have a
minimum initial torque of 6.2 Nm (55 In.-Lb.).

Pulling locknuts down tight will
cause valves to hitpistons when
making valve clearance adjustment. Do not run the
rocker arm nuts down with an air wrench. Using an
air wrench to remove or install locknuts will
destroy the self-locking feature.
FEELER GAUGE

gauge between rocker arm and valve stem (Figure 6).
Press down lightly on push rod end of rocker arm.
Make certain rocker arm is properly seated on push
rod. If feeler gauge cannot be inserted, loosen
rocker arm locknut on top of rocker arm. Tighten
rocker arm nut until feeler gauge can be inserted
and withdrawn with a slight drag.
A. After positioning number one cylinder adjust
intake and exhaust valves listed in Table 1.

8. Turn engine in a clockwise direction 360' (1
revolution)from position used in Step A. Adjust
intake and exhaust valves listed in Table 2.

TORQUE WRENCH

Hydraulic Tappet Valve Lash Adjustment (Begin
Spec D)
With hydraulic tappets the valve lash is zero, however
an initial adjustment is required. Adjust valves by
inserting a 0.05 mm (0.002 inch) feeler gauge between
valve stem and rocker arm. If feeler gauge cannot be
inserted, loosen rocker arm locknut on top of rocker
arm. Make certain rocker arm is properly seated on
push rod. Tighten rocker arm locknut until feeler gauge
can be inserted and withdrawn with a slight drag.
A. After positioning number one cylinder adjust
intake and exhaust valves listed in Table 1.
FIGURE 6. VALVE ADJUSTMENT

5. Turn engine in direction of rotation(clockwise when
viewed from the front of engine) until number one
cylinder is on a compression stroke and the 0' TDC
mark on flywheel or front crankshaft pulley lines up
with the timing indi~ator.

8. Turn engine in a clockwise direction 360' (1
revolution) from position used in Step A. Adjust
intake and exhaust valves listed in Table 2.

TABLE 1
VALVE TAPPET ADJUSTMENT
C. Turn engine in a clockwise direction 45' (1 /8
revolution) from position used in Step B.
Valve
Intake
Exhaust
Intake
Exhaust
Intake
Exhaust
Intake
Exhaust

D. Turn each rocker arm locknut, clockwise, two
full revolutions. This will preset the hydraulic
tappets into their proper operating position.
E. If used tappets are installed, that have not been
cleaned, the tappets will be full of cold used
engine oil. With cold engine oil the tappets will
leak down at a very slow rate during the
adjustment procedure. This may cause the
valves to open when Step D is performed.

7. Replace all parts removed in Step 2. Torque all
bolts.

Four
Cylinder

Six
Cylinder

X
X
X

X
X

2
2
3

X
X

TABLE 2
VALVE TAPPET ADJUSTMENT

Starting engine before tappets
have completely leaked down
will cause valves to stay open, causing valves
to strike pistons. Before cranking engine turn
crankshaft a minimum of two revolutions by
hand to ensure that the valves do not strike the
pistons.

6. Replace rocker arm cover using new capnut gaskets
and rocker cover gasket.

Threa
Cylinder

- The cylinders are numbered from front to rear.

Because of this the best procedure is to always
disassemble, clean and lubricate used tappets
before valves are adjusted.

F. After initial start-up allow engine to idle a
minimum of five minutes. This allows the tappets
to return to their normal operating position.

Cylinder
Number*

Valve
lntake
Exhaust
Intake

Intake
Exhaust
Intake
Intake
Exhaust

i
1

T
h
;
Cylinder

Cyliider
Number'

r;F
Cylinder

Cylinder

X
X

5
6
6

- The cylinders are numbered from front to rear.

X
X

VALVES
Intake and exhaust valves are made of alloy steel. The
exhaust valves are chrome-cobalt faced with hardened
exhaust valve seats pressed into the cylinder head.
Valve guides are pressed into cylinder head to hold the
valves in alignment with the valve seats. Valve springs
are held in place on the upper end of each valve stem by
spring retainers and locks. The lower end of each valve
spring is centered with a thin washer.
The rocker arms are mounted on studs that thread into
the cylinder head. The rocker arms pivot on rocker arm
balls that are retained with a hardened washer and a
self-locking hex nut. The push rods extend down
through cylinder head and block, into the tappets. The
upper end of each push rod sets in a recess in one end
of the rocker arm.

Inspection and Repair
Clean carbon from the valves, valve seats, valve
guides, and cylinder head ports. Remove all oil and
crankcase deposits from rocker arm assemblies and
push rods by washing in solvent.

ValveStem Seals: Do not reuse valve stem seals. Each
time the valves are removed from cylinder head, a
new seal must be used when valve is reinstalled.
Valve Stem Cap: Inspectvalve stem caps for cracks and
wear. Replace valve stem cap if it is cracked or worn.
Valve stem caps may be installed on Spec A to C
engines not originally equipped with valve stem caps. A
minimum clearance of 0.05 mm (0.002 inch) must be
maintained between valve stem cap and valve lock
collet (Figure 7).

Adjustment is achieved by turning rocker arm nut up or
down until correct valve lash is obtained between valve
stem and rocker arm.

VALVE STEM CAP

COLLET

Valve stem caps are used on most Spec A to C engines
to decrease contact stress between rocker arm and
valve tip.

0.05 mm

;

(0.002~ n c h )

.,..,

- ..

i--i,ccfz2.:.

VALVE
STEM

----,-

Valve Removal
1. Remove cylinder head. Refer to Cylinder Head
Removal procedure.

2. Place cylinder head on a solid bench with exhaust
side down.
Place valves. springs, retainers and wear platesina rack as they
are removed from cylinder head ao they can b. identified and
reinstalled in th.k orighal b d l o m O
i old valve stom
seals and replace with new o r m during assembly.

4
::

YT-1033

FIGURE 7. VALVE STEM CAP CLEARANCE

Tappets: Refer to Tappets found later in this section
for removal, inspection and installation of tappets.

valve spring retainers, valve springs, and valves.

Valves: Replace valves if they are cracked. bent,
burned, warped. or stems are worn. Use a micrometer
to measure diameter of valve stem. Measure inside
diameter of valve guide with a telescopic gauge and
micrometer. Check valve stem to guide clearance by
subtracting the valve stem diameter from the valve
guide inside diameter. Refer to SECTION 2, DIMENSIONS AND CLEARANCES for valve stem diameter,
valve guide diameter, and clearances. If valve stem is
worn, replace the valve. Replace valve guide, if
excessive clearance is still present using a new valve.

5. Remove valve spring wear plates or spacers and
valve stem seals. Remove valve rotators when used.

Refinish valves that areslightly pitted or burned on an
accurate valve grinder. If they are badly pitted or have
a thin margin when refacing, replace them.

3. Using a valve spring compressor. compress valve
springs and remove valve spring retainer locks.
4. Release valve spring compressor tool and remove

Guides: Worn valve guides may be removed by pressing them out through the bottom of cylinder head
using a valve guide removal tool (Figure 8) and
hydraulic press.

FIGURE 9.

FIGURE 8.

REMOVING VALVE GUIDE

INSTALLINGVALVE GUIDES

Each time the rocker arm locknuts are removed the
rocker arm stud threads must be inspected for wear.
Test for stud thread wear as follows:
1. Use a torque wrench to measure the rocker arm

The exhaust valve guide is 6mm longer (.2362 inch)
than the intake valve guide. Guides must be installed
in the correct guide bore.
Press new valve guides into position from the top of
cylinder head with an Onan valve guide installationtool
and hydraulic press. Install replacement valve guides
with grooved end up. To use tool, place cylinder head in
a hydraulic press with head gasket surfacedown. Place
valve guide driver pilot into valve guide. Insert installing
tool and guide into guide bore in cylinder head and
press downward until driver rests on machinesurfaceof
cylinder head (Figure 9). Valve guide must protrude a
specific distance above cylinder head. Measure from
machined surface around valve guide to the top of
guide.
The bore of a replacement valve guide is 7.63 to
7.74 mm (0.3004 to 0.3047 inch). The interference fit
of a guide in cylinder head is. 0.025 to 0.065 mm
(0.0009 to 0.0026 inch). The valve guide bore will
close some W e n installed. Use a valve guide reamer
to resize valve guides after installation to the correct
inside diameter. Do not ream or hone guides already
installed in service replacement cylinder heads. Valve
seats must be refinished after installing new valve
guides.

Rocker Arm and Stud: Check rocker arms for cracks,
galling, scoring, or wear. Replace the rocker arm and
ball ifexcess~velyworn.

locknut breakaway torque from operating position.
2. Use the torque wrench to remove rocker arm
locknut, and observe any increase in torque.
3. If the removal torque increases more than 2.3 Nm
(20 In.-Lb.) above the breakaway torque measured in Step 1, replace the rocker arm stud.
To replace a worn or damaged rocker arm stud,
unscrew the stud using the lower nut. Coat lower
threads of new stud with oil and install. Rocker
arm studs are installed starting with a long stud
on each end then a short, long, short, etc. ending
with two short studs in center of head (Figure 9a).

SHORT ROCKER ARM STUD

LONG ROCKER ARM STUD

FIGURE 9.. ROCKER ARM STUD LOCATION

Rocker Arm Balland Locknut: Inspect rocker arm balls
for cracks and wear. Replace rocker arm ball and arm if
it is cracked, worn, or damaged.
Rocker arm locknuts should be replaced each time
they are removed. Replace rocker arm studs, if after
installing new locknuts a minimum wet torque of
3.4 Nm (30 In.-Lb.) cannot be held. New, well oiled
rocker arm locknuts should have a minumum initial
torque of 6.2 Nm (55 In.-Lb.), when installed on new
rocker arm studs.

Spring: Check valve springs for cracks, worn ends,
distortion and tension. Ifspring ends are worn, check
lower valve spring wear plate and valve spring
retainer for wear. Check for spring distortion by placing spring on a flat surface next to a square. Measure
height of spring and rotate it against square edge to
measure distortion. Ifdistortion exceeds 2 mm (.0787
inch) replace spring. Check spring tension at the
installed height for both the valve open and closed
position using an accurate valve spring tester.
Replace any valve spring that is weak, cracked, worn
or distorted.
Valve Seats: Most naturally aspirated engines do not
have intake valve seat inserts. If intake seat area is
extremely worn and cannot be reground to specifications, machine cylinder head to receive a valve seat
insert. See Table 3.
Inspection and Removal: lnspect valve
seat inserts. If they are loose, cracked or
severely pitted, new ones must be installed. Remove valve seat inserts using a
valve seat removal tool (Figure 10).

Installation: If it becomes necessary to
replace valve seat inserts, or install intake
valve seat inserts, a press fit must be marntained (seeTable 3) between the new inserts
and insert bores in cylinder head. If insert
bores in cylinder head are damaged or worn
so that a press fit cannot be obtained when
installingnew standard size valve seat inserts,
the bores must be machined for an oversize
seat. Oversize intake and exnaust seats are
available in 0.25 mm (0.009 inch) and 0.50 mm
(0.01 9 inch).
Refer to Table 3 for the O.D. of valve seat
inserts, corresponding1.0.of bores in cylinder
head, and depth of counterbore.
The depth of counterbore in cylinder head
for valve seat inserts is measured from
gasket surface of cylinder head.
Install valve seat inserts as follows:
1. Thoroughly clean valve seat counterbore and remove any burrs.

2. Using wooden blocks to support cylinder head, place head on a bench
bottom side up.
3. Ensure that counterbores are clean
and start an insert into bore (valve seat
side up).
4. Use the appropriate valve seat insert
installation tool (intake or exhaust)
and drive insert down tightly into
counterbore.

5. It will be necessary to refinish valve
seat inserts with a grinder before
installing valves.
TABLE 3
VALVE SEAT INSERT
MACHINING SPECTFlCATlONS
VALVE SEAT
INSERT
Std. Sin

FIGURE 10. RlE(OVlNG VALVE SEATS
I"

O.D. OF
NEW INSERT
37.00 to
Wmust
37.W mm
~ E x h a u d
0.25 mm
37.25 to
3728 mm
0.50 mm
- 3 7 3to
37.53 mm
Std. Siu Intake
40.37 t o
40.40 mfn
Omdze Intake
0.25 mm
40.62 to
40.65 mrn
0.50 mm
40.87 to
40.90 mm

INSERT BORE
IN CYL HEAD
36.93 to
36.95 mm

DEPTH
8 49 to
8 59 mm

3718 to
37 20 mm
37.43 to
31.45 mm
40.30 to
40.32 mm

8 49 to
8.59 mm
8 49 to
859 mm
8.40 to
8.50 mm

40 55 to
40.57 mm
40.80 to
40 82mm

8.40 to
8 50 mm
8 40 to
8 50 mm

~ o d :Clean all push rods in a su~tablesolvent. On
rods with an 011 passage, blow out the passage
a" Check push rod ends for wear or
damage Check push rod for bends by rolling it on a flat
surface if push rods are bent, twisted, or damaged, they
s,t,
be replaced
valve Rotators: Posltlve Valve rotators are used on
some engrnes The valve rotator IS located below the
valve spring ~nthe cylinder head. There IS no easy way
to determine lf a valve rotator 1s good or bad. Onan
that valve rotators be replaced at each
major overhaul or if a bulld-up of carbon 1s noted on
valve face and valve seat.
push RodGuide P1ates:lnspect push rod guide plates. ~f
holes ~nguide plate are worn or burred replace guide
plate and push rod.

VALVE STEM SEAL

Do not remove valve after seal
Is installed. Valve can be withdrawn o n l y as far as the groove in valve
stem. Do not allow valve stem seal to come in
contact with groove or seal damage will result.

VALVE
VALVE

STEM

SEAL PROTECTOR

FIGURE 12. VALVE STEM SEAL INSTALLATION

- - --

FIGURE 11. VALVE SEAL PRO1ECTOR

Valve Assembly
1. Lubricate the stem of each valve and insert into
the guide from which it was removed.

5. Using a valve spring compressor, compress each
valve spring and retainer.

2. Install valve spring wear plate, spacer, or rotators
over valve guides into recess of the head.

6. Insert valve spring retainer locks and remove
valve spring compressor tool.

3. Place a clear plastic seal protector 'over valve
stem (Figure 11).

7. Install cylinder head with new gasket. Refer to
Cylinder Head installation procedure.

Do not reuse valve stem seals. Each time the valves are
removed from cylinder head, a new seal must be used when
the valve is reinstalled.

4. Coat inside of valve stem seal with oil. Push valve

stem seal over seal protector and all the way onto
valve guide flange (Figure 12). Remove seal protector from valve stem. Save for reuse on other
valves.

VALVE FACE AND SEAT GRINDING
Before installing new valves or previously used
valves, inspect valve seats for proper valve seating. If
used valves are reinstalled, the valve stems should be
cleaned and valve faces ground to their specified
angles of 44O for exhaust valves and 29' for intake
valves. Refinish intake valve seats to a 30' angle and
exhaust valve seats to a 45" angle. When refacing
valves and seats, remove all evidence of pitting and
grooving. If end of valve stem is pitted or worn, true it
and clean it up on the refacer wheel. Avery light grind
is usually enough to square stem and remove any pits
or burrs. A minimum clearance of 0.05 mm (0.002
inch) must be maintained between valve stem cap
and valve lock collet. If clearance is less than 0.05 mm
(0.002 inch) replace valve. The valve guide should be
thoroughly cleaned. If valve guide is worn, or valve is
warped, the necessary parts must be replaced.
By grinding the valve face and seat at slightly different angles, a fine line of contact on face and seat is
obtained, eliminating the need to lap the seating surfaces. The one degree difference in angles is defined
as the interference angle. The seat angle is greater
than that of the valve face. This assures contact at the
maximum diameter on valve seat seating surface.
Refinish intake valve faces to a 2Q0angle and exhaust
valve faces to a 44' angle on a valve refacing
machine. The first cut from valve face must be a light
grinding. Check if there is an unevenness of metal
being removed. If only part of valve's face has been
touched, check to see if valve is properly seated in
machine or if valve is warped, worn, or distorted.
When cut is even around the whole valve face, keep
grinding until complete face is ground clean. Besure
the correct valve face angle is maintained. When
valve head is warped, a knife edge will be ground
(Figure 13) on part or all of the head due to the large
amount of metal that must be removed to completely
reface valve. Heavy valve heads are required for
strength and good heat dissipation. Knife edges lead
to breakage, burning, and pre-ignition due to heat
localizing on the edge.
WARPED
VALVE WITH
KNIFE EDGE

KNIFE EDGE

GOOD MARGIN

Replace any valve that cannot be entirely refaced
while keeping a good valve margin (Figure 13) or is
warped, worn, or damaged in any way. The amount of
grinding necessary to true a valve indicates whether
valve head is worn or warped.
When refinishing intake valve seats that do not have
inserts, use a fine stone only. Using a coarse stone
may remove too much material too rapidly, resulting
with a head that must be machined for intake valve
seat inserts. If intake valve grinding specifications
cannot be maintained on a cylinder head that does
not have intake valve seat inserts, machine the head
to receive inserts.
When new valve seats are installed, or previously
used seats reground, refinishing must be done with a
valve seat grinder used according to the manufacturer's directions.
The following tools are required to assure accurate
valve seating:
1.
2.
3.
4.
5.

Valve seat grinder.
Dial indicator (valve seat runout).
Pilot tool.
Four fine grinding stones: 15O, 30°, 45O, and 60".
Valve refacer.

To assure correct valve seating, the following tolerances must be verified before and after valves and
seats are replaced or refinished:
1. Depth: Distance from cylinder head gasket surface to top of valve head. This depth must be
0.48 mm to 1.13 mm (0.0189 to 0.0445 inch) for
intake valves and 0.67 to 1.33 mm (0.0264 to
0.0524 inch) for exhaust valves.
2. Runout: This is the concentricity of seat relative
to the valve guide. The total runout of a good seat
must not exceed 0.050 mm (0.0019 inch).
3. Width: Width of seat should be 0.88 to 2.30 mm
(0.0346 to 0.0901 inch).

Gaind intake seats to a 300 angle as follows:
Remove carbon from valve seat area.
Grind seat with a 3W stone until a uniform seat
..
.
appears on the surface.
*
LDress stones frequentjy during seat grinding to
assure proper cutting angles.

FIGURE 13. VALVE HEAD MARGIN

3. Refinish intakevalve face toa2g0 angle and place
valve in the appropriate valve guide.

Measure valve head depth (Figure 14). If -this
depth is less than 0.48 mm (0.0189 inch), grind
seat until a depth of 0.48 mm (0.0189 inch) is
obtained. If valve head depth is greater than
2.13 mm (0.0839 inch) with a new valve, replace
seat insert or have the cylinder head machined to
receive a valve seat insert.
GRINDING
STONE

PILOT
TOOL

?EPTH GAUGE

6. Remeasurevalve head depth. If depth is less than
0.48 mm (0.0189 inch) repeat Steps 4 and 5. If
depth exceeds 2.13 mm (0.0839 inch) replace or
install new valve seat inserts.
7. Mark seat with a black felt marker or machinist
blueing.
8. Use the 4 5 O stone and lightly grind seat.
9. Use the 15' stone and lightly grind seat until seat
width is 0.88 to 2.3 mm (0.0346 to 0.0906 inch).
10. Clean seat and remark with black marker
11. Hand turn a 30' stone on the seat.
12. Recheck seat width (Figure 16).

METRIC
SCALE

5. Use a dial indicator (Figure 15) to measure valve
seat runout. Set dial indicator at zero and rotate
indicator to check runout of valve seat. If runout
exceeds 0.050 mm (0.0019 inch), grind seat until
the runout is less than 0.050 mm (0.0019 inch).

TURN INDICATOR
TO CHECK RUNOUT
OF VALVE SEAT

FlGURE 15. CHECKING RUNOUT OF VALVE SEAT

FIGURE 16. MEASURING SEAT WIDTH

bats to a 45' angle as follows:
n from valve seat area.
.,,rn a 45' stone until a uniform seat
,ar~on the surface.
Dress stone frequently during seat grinding to
assure proper cutting angles.
3. Refinish exhaust valve face to a 44' angle and
place valve in the appropriate valve guide.
4. Measure valve head depth (Figure 14). If this
depth is less than 0.67 mm (0.0264 inch), grind
seat until a depth of 0.67 mm (0.0264 inch) is
obtained. If valve head depth is greater than
2.33 mm (0.0917 inch), replace the valve seat
insert.
5. Use a dial indicator (Figure 15) to measure valve
seat runout. Set dial indicator at zero and rotate
indicator to check runout of valve seat if runout
exceeds 0.050 mm (0.0019 inch), grind seat until
runout is less than 0.050 mm (0.0019 inch).

6. Remeasure valve head depth. If depth is less than
0.67 mm (0.0264 inch) repeat Steps 4 and 5. If
depth exceeds 2.33 mm (0.0917 inch) replace or
install new valve seat inserts.
7 . Mark seat with a black felt marker or machinist
blueing.
8. Use the 60' stone and lightly grind seat.
9. Use the 30° stone and lightly grind seat until seat
width is 0.88 to 2.3 mm (0.0346 to 0.0906 inch).
10. Clean seat and remark with black marker.
11. Hand turn a 45' stone on the seat.
12. Recheck seat width (Figure 16).
Check valves for a tight fit to the valve seat with an
air-pressure-type testing tool. The seat width and
contact pattern can also be checked using blueing. If
there are any uneven spots. regrind the seat. Do not
lap the seats with grinding compound since this may
destroy a good grinding job.

CRANKSHAFT PULLEY AND DAMPER
The type of crankshaft pulley used on this series of
engines is designed to use a damper when required.
Remove the six damper retaining capscrews and
work damper and adapter off pulley before removing
pulley on some six cylinder engines.

1-1

DO not use a hammer or jaw type
puller to remove vibration damper.
Dents, bends, or cracks in damper from using the
incorrect removal procedure will damage it.

Pulley Removal
If engine is installed in a unit, determine if puller can
be used without first removing radiator. If the radiator
must be removed, drain cooling system, remove
components necessary to remove radiator, and
remove radiator.
1. Release tension on water pump and alternator

drive belts and remove belts.
2. Loosen crankshaft pulley retaining capscrew and
turn it out approximately 13mm (SO inch).
3. Thread two M I 0 x 45 Lg capscrews through puller
into tapped holes in pulley (Figure 17).

FIGURE 17. CRANKSHAFT PULLEY REMOVAL

4. Tighten puller screw. To assist in loosening pulley hub from crankshaft, strike puller screw with a
soft faced hammer.
5. Remove puller tools, crankshaft pulley retaining
capscrew, washer, and pulley.

Pulley Installation
1. Remove any burrs, if necessary, from crankshaft.
Place woodruff key on crankshaft.
2. Position crankshaft pulley on crankshaft and
install washer and pulley retaining capscrew.
3. On engines equipped with a damper, slide adapter and damper on and secure with the six flat
washers and capscrews.
4. Install water pump and alternator drive belts.
Check for correct belt tension. Refer to SECTION
9, COOLING SYSTEM.
5. Install all parts removed during disassembly.

Vibration Damper
Replace vibration damper if it is bent, cracked, has
been dropped, or mishandled in any way. Onan also
recommends that thevibration damper be replaced at
each major overhaul. A failed vibration damper may
cause fan belt(s) to flip over, excessive gear train
wear, or crankshaft breakage.

FLYWHEEL AND RING GEAR
The flywheel is mounted on the crankshaft with six
flanged hex head capscrews. A hollow dowel pin
driven into flywheel ensures proper crankshaft to
flywheel alignment. The flywheel can be attached to
crankshaft in only one position. The starter ring gear
is shrunk onto flywheel rim.

Flywheel Removal
Remove any accessory that may be mounted to flywheel and flywheel housing before removing flywheel. It is not necessary to remove starter.
1. Remove capscrews that secure flywheel to

crankshaft flange.
2. Thread two capscrews in opposite holes of flywheel face to serve as handles.
3. Thread two M I 0 x 1.75 threaded rods into flywheel mounting bolt holes. This will support flywheel as it comes off the crankshaft flange.
4. Pull outward on capscrews threaded into flywheel (Figure 18) to remove flywheel.

THREADED
RODS

CAPSCREWS

Flywheel Inspection
Remove any burrs or nicks from flywheel surface
where it fits against crankshaft flange. If this surface
is not smooth and true, the flywheel may have a slight
wobble which will result in engine vibration. If a
clutch is mounted on engine, a scored or heat
checked flywheel face surface must be machined
smooth. Replace flywheel if more than 0.40 mm
(0.0157 inch) of stock must be removed. lnspect
engine clutch shaft pilot bearing located in flywheel
bore. If bearing is worn, drive it out. When installing a
new bearing, use a driver that will press against
bearing outer race and press bearing into position in
flywheel.

Ring Gear Inspection, Removal, and
Installation
1. lnspect flywheel ring gear for cracked, chipped.

or broken teeth. Ring gear must be replaced if any
of these conditions exist.
2. To remove a flywheel ring gear proceed as
follows:
A. Grind through ring gear at the base of one of
the teeth until ring gear separates.
6 . Expand ring gear and drive ring off flywheel
using a drift and hammer. Work around the
circumference of ring gear to avoid binding
ring on flywheel.
3. To install a new flywheel ring gear, proceed as
follows:
A. The ring gear is expanded and allowed to
shrink onto flywheel by uniformly heating the
gear to 185" to 195"C (365" to 383" F), then
placing it on flywheel.

Do not heat ring gear to a
warp and the heat treatment will be
destroyed.
FIGURE 18. FLYWHEEL REMOVAL

If the flywheel cannot be removed with a direct pull
and shaking of handles, it may be necessary to
remove starter and tap flywheel loose. Turn flywheel
and tap exposed area at intervals until flywheel
comes loose.

B. Drive ring gear down tight against shoulder
on flywheel. Do it fast and do not damagegear
teeth. The ring will contract rapidly and may
shrink to flywheel before it is in place. If this
occurs, a new ring gear will be required.

F1~wh-l Installation
Make sure dowel pin is lined up and install flywheel
by reversing the removal procedure. Secure flywheel
in twosteps by tightening capscrews to a torque of 68
Nm (50 Ft.-Lb.) using a qtarpattern torque sequence.

FLYWHEEL HOUSING
The flywheel housing is a one piece casting that is
positioned on rear of cylinder block with two dowel
pins. The housing is secured to cylinder block with
capscrews and flat washers.

5. lnspect dust seal located between flywheel housing and rear seal plate. Replace, if necessary.
6. By reversing the removal procedure, assemble
flywheel housing to rear of block.
7. Check flywheel-to-flywheel housing runout as
follows:

Removal, Inspection, and Installation
The only time the flywheel housing may require service or replacement is when it is cracked or damaged.
To remove flywheel housing from engine, proceed as
follows:
1. Removeany accessory attached to rear of engine.
2. Remove flywheel. Refer to Flywheel Removal
procedure.
3. Remove capscrews and washers securing flywheel housing to engine. Tap housing with a soft
hammer to break it loose from the positioning
dowels then remove housing. Remove starter
from flywheel housing.
4. lnspect housing for cracks and other damage.
Replace housing if it is damaged.

A. Load crankshaft so that all endplay is taken
UP.
6. Mount a dial indicator on face of flywheel.
C. Adjust indicator point so that it rests on flywheel housing face perpendicular to flywheel
face. Set dial indicator to zero.
0. Keeping endplay removed, rotate crankshaft
one complete revolution to determine runout.
E. If runoutexceeds .15 mm (.0059inch) remove
flywheel and flywheel housing. Use a straight
edge and feeler gauge to check for warpage
on flywheel housing face and mounting
surface.

CRANKSHAFT REAR OIL SEAL
AND WEAR SLEEVE
The rear oil seal is a spring-loaded, single lip type
pressed into an aluminum alloy rear seal plate. Rear
seal plate assembly mounts on the back of cylinder
lock under block flywheel housing. A steel wear
sleeve is used to protect the crankshaft. The use of a
wear sleeve increases seal life and reduces crankshaft
wear. The sleeve is pressed onto the crankshaft
flange and secured with Loctite number 271.

3. Apply Loctite number 271 to crankshaft and
inside of new wear sleeve before installing. Position wear sleeve on crankshaft flange with outside
chamfer toward the back of engine.
4. Using the rear wear sleeve installing tool (Figure
20), press wear sleeve onto crankshaft flange.
Alternately tighten the bolts until tool bottoms on
crankshaft flange.
REAR WEAR
SLEEVE INSTALLATION
TOOL

Seal Removal
1. Remove flywheel and flywheel housing from the

2.
3.

engine. Refer to Flywheel Removal and Flywheel
Housing Removal procedures.
Remove capscrews from face of seal plate.
Remove four capscrews on back end of the oil
pan and loosen capscrews along each side of oil
pan.
Slide seal plate off crankshaft flange. Be careful
not to damage oil pan gasket.
Support seal plate assembly and drive old seal
out.

Wear Sleeve Removal and Installation
1. Inspect wear sleeve for nicks, burrs, and wear

grooves. Replace if necessary.
2. If replacement is required, use a hammer and a
chisel that is only as wide as wear sleeve, to make
one or two chisel marks across wear sleeve (Figure 19). This will expand wear sleeve allowing
removal from crankshaft.

Do not nlck or gouge the crankshaft with chlmi. If crankshaft
h damaged It must be removed and repalfed or
replaced.
WEAR
SLEEVE

CHISEL MARK
I

FIGURE 20. WEAR SLEEVE INSTALLATION

5. Clean any surplus Loctite off the wear sleeve and
crankshaft flange.

Seal Installation

1. Lubricate new oil seal with oil to ensure sufficient

lubrication until crankcase oil enters seal.
2. Using oil seal driver, install a new seal with the
rubber lip facing outward (open side of seal
inward). See Figure 21. Drive new seal in flush
with the machined surface of seal plate.

A new seal must be Installed
me
seal should not be positioned in a wear groove on
wear 8leew. Posltionlng a seal on a worn, dirty
rough, or grooved crankshaft surisce will cause
seal to leak.

IPCAUM)N w/M a new wear simve.

SEAL PLATE
ASSEMBLY

FIGURE 2 2 REAR SEAL PLATE INSTALLATION

6. Torque seal plate capscrews and oil pan.
7. Check crankshaft-to-seal runout as follows:

FIGURE 21.

INSTALLING SEAL IN SEAL PLATE

3. Make certain wear sleeve on which seal rides is
free of dirt, nicks, burrs, and wear grooves.
4. Lubricate crankshaft flange with clean engine oil.
Apply a bead of "RTV" Sealant to the junction of
cylinder block, seal plate, and oil pan.
5. Push seal plate assembly onto crankshaft (Figure
22). Use extreme care when installing seal plate
so the oil pan gasket is not damaged. If oil pan
gasket is damaged, remove oil pan and replace
the gasket.

A. Load crankshaft so that all end play is taken
UP.
8. Mount a dial indicator on face of crankshaft
flywheel mounting flange (Figure 23).
C. Rotate crankshaft one complete revolution.
Note maximum runout.
D. If runout exceeds .25mm (.0098 inch) remove
seal plate assembly and reposition seal in
plate.
8. After the correct crankshaft-to-seal runout is
obtained, install flywheel housing, flywheel, and
any other components removed during disassembly.

SEAL

Forcing plston from cylinder

IPCAUTK)N beton sleanlng carbon or re-

CONNECTING ROD
AND PISTON ASSEMBLY

Onan L engines use high strength aluminum alloy
pistons with top ring groove protection. Each piston
is tapered and fitted with two compression rings and
an oil control ring. Full floating piston pins connect
the piston to its connecting rod. The pins are held in
place with a snap ring at each end.
Keystone pistons are used in all turbocharged
engines. A relief in the turbocharged piston skirt
provides clearance for the oil spray nozzle. Pistons
for use in naturally aspirated engines cannot be
installed in engines equipped with piston cooling
jets.
High speed turbocharged engines have hard anodized
piston crowns.
The connecting rods are made of tapered, I-beam
section, heat treated steel. A funnel shaped hole in
upper end of each rod catches oil that is splashed or
sprayed within the cylinder block and allows it to flow
into connecting rod bushing for continuous piston
pin lubrication.
The lower end of each connecting rod contains halfshell precision bearings and the upper end is fitted
with a steel backed bronze bushing. The precision
type connecting rod bearings are replaceable without machining.

Removal and Disassembly
Replacement of connecting rod bearings can be
done without removing piston and connecting rod
assemblies. If replacing only the rod bearings, follow
Steps 1 and 4.
1. Drain crankcase oil, remove oil pan, and oil
pickup tube. See SECTION 8. OIL SYSTEM.
2. Remove cylinder head. Refer to Cylinder Head
Removal procedure.
3. Remove carbon from top of cylinder bore and
check for a ridge. Remove ridge (Figure 24) with
a ridge reamer before attempting piston removal.
Uslng 8 rldge m m e r to remove

cyllnder bore.

RIDGE
REAMER

moving ddge may cause damage to pkton land8
and break rings.
4. Turn crankshaft until piston isat the bottom of its

stroke and remove connecting rod nuts. Remove
bearing caps and free lower end of connecting
rods from crankshaft. Remove bearing shells
from bearing caps and connecting rods.
Mark and number each piston and rod assembly so it can be
returned to its respective cylinder after overhaul. Keep connecting rod bearing ups with their respective rO&. The rod
and cap m marked with the ume identifying characters.

5. Push rod and piston assembly out through top of
cylinder using a hammer handle. Avoid scratching crankpin and cylinder wall when removing
piston and rod (Figure 25). Protect crankshaft rod
journals by placing a piece of rubber tubing over
rod bolts during removal.

- ROD

BOLTS

RUBBER
TUBING

6. Remove piston rings with a piston ring spreader
as shown in Figure 26.

RING
SPREADER

RING

Do not use a caustlc cleanlng solvent or wlre brush for cleaning plston*. These materials wlll cause piston damage.

FIGURE 26.

Remove dirt and deposits from piston surfaces with
an approved cleaning solvent. Clean piston ring
grooves with a groove cleaner or the end of a piston
ring filed to a sharp point (Figure 28). Care must be
taken not to remove metal from the ring groove sides.

ACAUnON

dEMOVlNG PISTON RINGS

7. Using a pair of snap ring pliers, remove piston pin
retainers and push piston pin out (Figure 27).

PISTON
PIN
RETAINER

FIGURE 28. PISTON GROOVE CLEANING

Inspection (Piston, Rings, and Cylinder Bore)

The following text contains inspection procedures
concerning pistons, rings, and cylinder bores.
;

Xn s
b
&. ,

T~7i

-:-A

.-zg$=~z
*,:-;*y;:.-

FIGURE 27. REMOVING PISTON PIN RETAINER

1. Piston Inspection
After cleaning, e m i n e the piston for score
marks, damaged ring groovers. or signs of overheating. Inspect pistons for cracks in the head or
skirt area? and for bent or broken ring lands.
mmaify show upas cracks

-a=

Some minor surface cracks may -appear on the
p W & W qf -.speed
tqbocharged engine
pistons, this is normal. -

A. Check for ring groove wear by installing a
new ring in top ring groove. Insert a feeler
gauge between new ring and the land to
check clearance (Figure 29). Keystone ring
groove wear must be checked using special
gauge pins (Figure 29).

2. Piston Ring Clearance
A. Ring end gap should be measured before the
rings are installed on pistons. Insufficient end
gap will cause scored rings and cylinders.
Excessive end gap will cause additional oil
consumption and blowby.
B. Check ring end gap by inserting each ring into
cylinder in the location it is to be used. Use a
piston to push ring squarely down in cylinder
bore far enough to be in the ring travel area.
Check ring end gap with a feeler gauge.

C. The practice of filing ring ends to increase end
gap is not recommended. If ring end gap does
not meet specifications, check for the correct
set of rings and correct bore size. A cylinder
bore that is 0.03 mm (0.0012 inch) under size
will reduce the end gap 0.08 wm (0.0031 inch).
3. Calculating Piston to Cylinder Wall Clearance

MICROMflER

KEYSTONE PISTON
NEW
RING

FEELER
GAUGE

Measurements of the pistons, cylinder bores, and
clearances between pistons and cylinder bores
should be taken at 21 OC (70°F). Pistons must be
fitted to their respective cylinder bores before the
rings are installed to provide a specific clearance.
A. Using an inside micrometer, dial bore gauge, or
telescopic gauge, measure the inside diameter
of cylinder bores. Measurement shouId be taken
halfway down the bore and at a right angle to
crankshaft axis. Refer to Cylinder Bore inspection for cylinder bore measuring procedure.

8. Using an outside micrometer, measure outside
diameter of piston skirt 13 mm (0.5. inch) below
oil ring at a right angle to the piston pin.

STANOAR0 PtSTON

FIGURE 29.

CHECKING RING SIDE CLEARANCE

B. Replace any piston that is badly scored or
burred, cracked, has badly worn ring grooves.
or otherwise is not in good condition.
C. Proper piston to cylinder clearance must be
maintained for satisfactory operation.
D. Check piston to cylinder bore clearances 90'
from the axis of piston pin and below oil control
ring when piston is in the TDC position.
If piston rings are r w v d from the cylinders, mn a h a

C. The difference between the two readings is the
piston to cylinder clearance. If clearance exceeds wear limit cylinder bore should be resized
to the smallest standard oversize diameter at
which it will clean up. Oversize pistons and
rings are available in 0.25 mm, 0.50 mm,
0.75 mm, and 1.OO mm.

Inspection (Connecting 'Rod and Bearings)
1. Clean connecting rod and cap of all oil and crankcasedeposits. Make c a n funnel oil hole is clean
and open.

2. Check connecting rods for nicks, cracks, and
damaged bolt threads. Replace as necessary.
3. Measure the outside diameter of piston pin and the

shortp.riadof~,donatd~the~rinQ8.
insidediameter of connectingrod bushing. Replace
ORon used rings wiH not so.1 properly. Now r i w wow or
l a p ~ e s t o % u r i b h ~ c y ~ w . I b e n d ~ ~ aconnecting rod bushing if clearance is greater than
specified.
p.riodof~opmdkn.

4. Inspect connecting rod bearing shells for scoring, chipping, cracking, or signs of overheating. If
any of these conditions are present, replace the
bearing shells. Backs of the bearing shells should
be checked for bright spots and replaced if any
bright spots are found. Bright spots usually indicate that the bearing shells have been moving in
the connecting rod.
5. Measure connecting rod bearing shells for wear
(Figure 30), with bearing shells installed and
connecting rod nuts torqued to85 Nm (63 Ft.-Lb.).

If crankshaft is worn or damaged and must be
reground on naturallyaspirated engines, rod bearings
are available in undersizes of 0.25 mm. 0.50 mm. and
0.75 mm.
,FUNNEL

Connecting Rod to Piston Assembly
1. Install one piston pin retainer in the piston pin

hole with sharp edge of retainer facing outward.
2. Insert upper end of connecting rod into piston,
with piston swirl chamber positioned opposite
connecting rod identification numbers (Figure
31).

IDENTIFICATION NUMBERS

SHAPED OIL HOLE

MEASURE IN DIRECTION
INDICATED BY ARROW

FIGURE 31. PISTON TO ROD ASSEMBLY

FIGURE 30. CONNECTING ROD

3. Lubricate piston pin and push it into piston and
connecting rod.
4. Install the other piston pin retainer with sharp
edge facing outward.
Due to the method of grinding and fillet rolling of the
turbocharged engine crankshaft, Onan recommends
that the crankshaft not be ground and used again in
turbocharged engines. Regrinding of a turbocharged
engine crankshaft for use in a naturally aspirated
engine is acceptable.

Connecting Rod Bushing Rephicement
If connecting rod bushing is worn, it must be pressed
out and a new one pressed into connecting rod. When
new bushings are installed, be sure oil hole lines up
with the connecting rod oil hole.
After installing a new connecting rod bushing, it must
be reamed to obtain the correct inside diameter. A
new piston pin installed in a new bushing at 21°C
(70° F) should be a thumb push fit.

Plston Ring Instellation: After piston rings have been
properly fitted to the cylinder bore, lubricate piston
and rings with engine oil. Install rings on piston,
using a piston ring installer as shown in Figure 32.
Whenever a connecting rod assembly Is secured In a vlse, be careful
that the bottom of plston skirt k not nicked. Use
pro tec tlve la ws, wooden blocks, or a cloth to protect
rod and plston from nicks, whlch may lead to plston
or connectlng rod failure.

RING
SPREADER

FIGURE 3 2 INSTALLING RINGS

1. lnstall oil control ring expander in bottom groove
of piston, with the guide pin inserted inside
expander.
2. Install chrome oil control ring in bottom groove
over expander, with end gap opposite (180
degrees) the guide pin in expander.
3. lnstall second compression ring in second
groove of .piston, with side stamped "Up 2nd" or
with a dot towards top of piston.
4. lnstall the top chrome compression ring or
keystone ring in top groove of piston with side
stamped "Up Top" or with a dot towards top of
piston.

Piston Assembly lnstallation
lnstall each piston, with rings and connecting rods,
as an assembly. Each connecting rod and bearing
cap should have been numbered during disassembly
for identification and must be installed in thecylinder
from which it was originally removed. lnstall piston
assembly in the engine with connecting rod identification numbers facing camshaft side of engine and
the piston swirl chamber towards intake side.
1. Stagger piston ring gaps evenly around piston

and apply lubricant to the piston and rings.
2. Turn crankshaft to position numberone rod bearing journal at the bottom of its stroke.
3. Position a bearing shell in connecting rod, with
tang of bearing shell in the recess of connecting
rod. Lubricate bearing shell and crankshaft journal. Protect crankshaft rod journals by placing a
piece of rubber tubing over rod bolts during
installation (Figure 33).

Make certain the backs of bearing shells and bearing seats a n
free from dirt and grit particles. Foreign materfsl
under a bearing shell will cause high spots and
early bearing failure.

4. Compress the rings with a ring compressor and
install piston assembly in cylinder bore by tapping on top of piston with a wooden hammer
handle (Figure 33).
If any difficulty is experienced in installing piston assembly,
the ring compressor must be removed and the ring set
inspectedfor correct installationin piston ring grooves. Align
lower end of connecting rod with crankshaft journal before
inserting piston assembly into cylinder bore.

5. Install a bearing shell in connecting rod bearing
cap, with tang of bearing shell in recess of bearing cap and lubricate.
6. lnstall bearing cap and shell, making certain identification numbers stamped in bearing cap are
located on same side as corresponding numbers
stamped in connecting rod.
7. lnstall and alternately tighten rod cap retaining
nuts in increments up to the specified torque of 85
Nm (63 Ft.-Lb.).
8. lnstall remaining piston assemblies in the same
manner. Turn engine over by hand after each
piston assembly is installed to see that all bearings are free.
9. lnstall oil pickup and oil pan with a new gasket.
10. lnstall cylinder head and adjust valve lash clearance. Referto Cylinder HeadInstallationprocedure.
11. lnstall rocker arm cover and replace crankcase
oil.

RUBBER
TUBING

FIGURE 33. PISTON INSTALLATION

CAMSHAFT ASSEMBLY
The camshaft is a high strength alloy iron casting
with hardened precision ground journals. Camshaft
assembly is located i n the cylinder block on left side
of engine. A thrust type retaining plate is used
between camshaft gear and shoulder of the first journal to position camshaft in cylinder block. Acamshaft
drive gear is positioned on the camshaft by a key and
retained in place with a press fit. Thecamshaft gear is
driven by the crankshaft gear through an idler gear.

Removal (With Cylinder Head Removed)

B. If engine is mounted in a unit, the tappets can
be held in their uppermost position by pulling
tappets up with a pencil magnet. Pull tappets
out of the tappet bore in cylinder block and
lay to one side.

7. Remove camshaft assembly.

Do not scratch or mar the camahan brrlngs wlth a m 10a t the cam8haft 18 wtthdmwn from cyllnder
block.

1. Remove valve cover and cylinder head assembly,

keeping rocker arms, tappets, push rods, etc. in
their proper order. Refer to Cylinder Head Removal procedure.
2. Remove the components necessary to gain
access to gearcase cover and remove cover.
Refer to Gear Cover Removal procedure.

3. Remove the mechanically operated fuel transfer
pump and push rod.
4. Check camshaft to idler gear backlash before
removing camshaft assembly.
5. Rotate camshaft gear so camshaft retaining plate
capscrews are accessible and remove capscrews.
6. Remove camshaft assembly.

Inspection
After removing camshaft assembly, check retaining
plate clearance (endplay) by inserting a feeler gauge
between retaining plate and camshaft gear. If endplay exceeds specifications with a new retaining
plate replace camshaft gear.
Visually inspect the intake and exhaust lobes for roughness, scoring or excessive wear. Using a micrometer,
check
lobes for wear by measuring the lobesfrom nose
:
to base (A to A). See Figure 34. If exhaust or intake lobe
measurementsare worn beyond specifications, replace
camshaft and tappets.

Be careful not to scmtch or mar
the amrkftboarlng8 wlth a m
lobe8 as camshatt k wlthdmwn from cylinder
block.

NOSE

Removal (Without Removing Cylinder Head)
1. Remove valve cover, loosen rocker arms and
remove push rods. Keep push rods i n their proper
order.
2. Remove the components necessary to remove
gearcase cover and remove cover. Refer to Gearcase Cover Removal procedure.
3. Remove mechanically operated fuel transfer
pump and push rod.
4. Rotate camshaft gear so camshaft retaining plate
capscrews are accessible and removecapscrews.
Before removing camshaft and gear, rotate
crankshaft until timing marks on idler gear.
crankshaft gear, and camshaft gear align.
5. Check camshaft to idler gear back lash, before
removing camshaft.
6. Before withdrawing camshaft from cylinder
block, position the tappets so they do not interfere with camshaft lobes during removal.

A. With the engine removed from application for
overhaul, simply turn engine on stand so front
of block is up then push tappets to their
uppermost position.

A BASE

flGURE 34. CAM-

L06E M U S U R M W

Check camshaft bearing journals for excessive wear
using a micrometer. If bearing journals are worn,
replace both the camshaft and bearings. lnspect
retaining plate for wear. Replace if thrust surface is
rough or wear is excessive. New retaining plate
thickness is 11.8mm to 12mm (.4646 inch to .4724
inch).

Camshaft Gear
To remove the camshaft gear, place camshaft assembly in a press. Support camshaft retainer and
push camshaft out of gear. lnspect gear for nicked,
scored or broken teeth. Replace if necessary.

Camshaft Bearings
The steel backed, alloy lined camshaft bearings are
the precision type which do not require machining
after installation. The camshaft bearings are a press
fir into the cylinder block and support the camshaft.
The camshaft bearings are lubricated through oil
passages from the main oil galley.

On engines with solid tappets the front bearing is wider
and has two oil holes in it. Be sure the two oil holes are
lined up, one hole with oil passage from main bearing
and the other with oil passage to rocker arm oiling
system.
On engines with hydraulic tappets the third cam bearing
has two oil holes and a circumferential groove. Be sure
the two oil holes are lined up, one hole with oil passage
from main bearing and the other with oil passage to
hydraulic tappet oil gallery. Third cam bearing must be
installed at a dimension of 214.2 to 214.8 mm (8.43 to
8.46 inch) from front face of cylinder block to the
forward edge of cam bearing. This will ensure alignment
of circumferential groove in third cam bearing journal.
Pull in the other bearings until oil hole is completely
visible through oil passage from main bearing (Figure 35). Reverse position of bearing puller and install
rear bearing, aligning oil hole with oil passage from
main bearing.
--

With camshaft removed, usea micrometer to measure
diameter of camshaft journals. Use a dial bore gauge
or a telescopic gauge and micrometer to measure
inside diameter of cam bearings. Replace camshaft
bearings if theclearance is greater than specified, the
bearings show cracks, or breaks.

Removal: The crankshaft and gearcase backplate
must be removed before cam bearings can be
replaced. Refer to Crankshaft and Gearcase Removal
procedures.

Wheninstalling the rear cam bearing,
use caution not to score or scratch
the other bearings since bearing puller must pass
through all of them. Place protective sleeving on
threaded puller shaft to protect bearings.
INSTALLATION
TOOL

CAM BEARING

1. Drive the camshaft rear plug out from the inside

3.
4.
5.

of cylinder block.
Assemble cam bearing puller through cylinder
block from the rear. Place shoulder of puller on
outside of front bearing. All bearings except the
rear one are pulled toward the rear of cylinder
block.
Gradually tighten puller nut until bearing is
removed from the block. Remove old bearing
from puller before removing the next bearing.
Remove the remaining bearings leaving the rear
bearing for last.
To remove rear bearing, reverse position of
puller, so rear bearing is pulled towards front of
cylinder block.

Installation: Pull new bearings into place using the cam
bearing puller. Start installing bearings at front (pullfrom
rear) leaving the rear for last. Cam bearings are pulled in
without lubrication.
Thecamshaft bearings must be propedy posifiwed in cylinder block so
oil hole in bearing lines up with oil passage in cylinder
block. Blockage of the bearing oil hole will cause early
bearing failure.

OIL HOLE IN
BEARING

- NGUBE 35. CAM BEARING INSTALLATION

Do not attempt to ream cam bearings as they are a
precision type. After installing rear bearing, insert a
new expansion ptug i n recess. Apply Permatexsealing
compound to edges and expand it into place with a
light blow to its center. A few light blows is all that is
normally required to install expansion plug. If the
plug is hit too hard and becomes concave it will
contact camshaft when installed. If plug touches
camshaft after installation remove plug and replace
with a new one.

GEAR
TIMING
MARKS

Camshaft Assembly, Installation and Timing
1. The camshaft gear is a press fit onto the cam-

shaft. To install camshaft gear to camshaft, proceed as follows:
A. Place camshaft in a press with shoulder of
front bearing journal resting on parallel bars.
6. Place camshaft retaining plate on camshaft
with flat machined surface toward journal
shoulder.
C. Install the key and press camshaft gear onto
camshaft until it bottoms on shoulder with no
clearance.
D. Check retaining plate clearance (endplay) by
inserting a feeler gauge between retaining
plate and camshaft gear.

2. Install crankshaft and mount gearcase backplate.
Refer to Crankshaft and Backplate installation
procedures.
3. Lubricate camshaft bearings in cylinder block
and carefully insert camshaft. Be careful not to
scratch or mar camshaft bearings.
4. Install capscrews through retaining plate and
tighten to the specified torque.
5. Align timing marks on idler gear with timing
marks on camshaft gear and crankshaft gear
(Figure 36) and install idler gear.

Line up single dot on Idler gear with slngh dot on mnkshafl
gear and two dots on Idler gear wlth two dots on amshafl
gear.
FIGURE 36. TIMING MARKS

6. Check camshaft gear backlash and camshaft
endplay.
7. Install all other parts, which were removed during
disassembly, by a direct reversal of the removal
procedure. See S E C l l O N 10, FUEL SYSTEM for
correct injection pump mounting and timing.

TAPPETS
The tappets are positioned in the cylinder block above
the camshaft. The top of each tappet is machined to
accept a push rod. The tappets ride on intake and
exhaust camshaft lobes, changing camshaft rotary
motion to a reciprocating motion opening and closing
the valves.

Removal
1. Remove rocker arm cover.

2. Remove rocker arm assemblies. Keep rocker arms,
rocker arm nuts and push rods in order, so they go
back in the same valve train position.
3. Remove cylinder head. Refer to Cylinder Head
Removal procedure.
4. Removetappets and identify them as to their location
in cylinder block so they can be reinstalled in their
original location.

lnspection Solid Tappet
Very little wear takes place on tappet diameters or in
tappet bores. If the clearance between tappet and bore
in cylinder block exceeds specifications, replace the
tappet.

Disassembly:
1. Hold the push rod socket down with a push rod, use
the blade of a small screwdriver to remove reta~n~ng
ring.

2. Remove push rod socket and metering plate.

3. Remove plunger and plunger spring.

Inspection: Thoroughly clean all parts in cleaning
solvent, and inspect carefully. If any parts are damaged
or worn the entire tappet assembly should be replaced.
If the tappet body wall is scuffed or worn, inspect the
cylinder block tappet bore, if the bottom of the tappet is
scuffed or worn replace the camshaft.
Assembly:
1. Place plunger spring and plunger in tappet body.

2. Lubricate, but do not fill, the assembly with clean
engine oil.
3. Install metering plate and push rod socket.
4. Press down on push rod socket with a push rod.
lnstall retaining ring.

The tappet is now completely assembled, lubricated
and ready for installation.

Installation
lnspect the tappet faces which contact camshaft lobes
for roughness, scuffing, or conclave wear. Replace any
worn tappets. If tappets are worn, replace tappets and
camshaft.

Hydraulic Tappet
lnspect and clean each tappet separately do not interchange internal parts. If any part of the hydraulic tappet
assembly needs replacing, replace the entire assembly.

1. Lubricate each cam lobe with a special cam and
tappet lubricant. New tappets are filled with a light
oil. This oil will not harm the engine and should not
be replaced before installation.

2. Lubricate the bottom of each tappet with a special
cam and tappet lubricant.

3. Install tappets in their original location in cylinder
block.
4. Install parts removed during disassembly, by a
direct reversal of the removal procedure.

GEARCASE COVER
The gearcase cover encloses the gear train and front
end of engine. A fuel injection pump gear cover plate
is installed over opening provided for it in the gearcase cover.

Installation
1. Inspect, clean, and remove any burrs from crank-

2.
3.

Removal
1. Release tension on fan belt. Remove belt, alterna-

2.
3.

5.
6.

tor, and alternator bracket.
Remove crankshaft pulley or damper assembly
and front engine support (if used).
Remove capscrews and Belville washers securing oil pan to gearcase cover. For ease of removal
and installation of cover, loosen the other oil pan
capscrewsenough to lower front end of oil pan. If
the oil pan gasket is damaged during removal of
gear cover, oil pan must be removed and gasket
replaced.
Remove fuel injection pump gear cover plate
capscrews and cover plate.
Remove capscrews securing gearcase cover to
back plate. Tap cover loose with a soft faced
hammer.
Remove gearcase cover from engine, being careful not to damage front portion of oil pan gasket.

shaft sealing surface.
Coat crankshaft lightly with lubricating oil.
Place a new gasket on back plate. Apply a bead of
"RTV" Sealant to the junctions of cylinder block,
oil pan, gearcase backplate, and gearcase cover.
Position gearcase cover on backplate. Complete
the installation of cover and related parts. Torque
all capscrews securing cover to backplate. Also
torque oil pan capscrews securing oil pan to
gearcase cover and block.
Install crankshaft pulley and damper assembly
when used.
Install and tighten fan belt. Refer to SECTION 9,
COOLING SYSTEM, Fan Belt Adjustment
procedure.

GEARCASE AND BACKPLATE
Located under gearcase cover on front end of engine
is a completely enclosed train of precision machined
helical gears. The crankshaft gear, which is pressed
and keyed onto crankshaft, drives two idler gears.
The lower (small) idler gear drives the oil pump drive
gear. The upper (large) idler gear drives both the
camshaft and fuel injection pump. The gear train is
splash lubricated by oil thrown by the rotating gears.
The gear train will run quietly if gears and bearings
are in good condition. The gear train may be exposed
by removing gearcase cover as described earlier in
this section.

ldler Gear and ldler Gear Shaft
(Cam and Injection Pump Drive)
The idler gear has a steel backed bronze bearing
pressed into it. This bearing is lubricated with engine
oil from the block. Oil travels through the center of
idler shaft and around retaining bolt toan oil passage
bored through the shaft to the bearing surface.
The idler shaft is pressed into the bore in cylinder
block. The idler gear and shaft are secured with a
large washer and capscrew that threads into cylinder
block.

Idler Gear Removal and Replacement:
1. Remove capscrew and washer retaining idler
gear.
2. Remove idler gear from shaft.
3. Inspect idler gear for nicked, worn, or broken
teeth. Replace if necessary.
4. Measurethe inside diameter of idler gear bearing.
Replace bearing if it is nicked, scored, or worn.
After pressing a new bearing into gear, ream to
the correct inside diameter.

Idler O.ar Shaft Remom1 and -R
lnspect
idler gear shaft. If shaft is worn or scored it must be
replaced. A slide hammerand metric adapter will aid
i n the removal of idler gear shaft.

1. To remove idler shaft, install a 14mm adapter in
end of idler gear shaft.
2. lnstall slide hammer into adapter and pull idler
gear shaft from cylinder block.
3. To install a new idler gear shaft, position it in bore
of cylinder block. Insert washer and retaining
capscrew into idler shaft. Tighten capscrew until
idler gear shaft bottoms in cylinder block bore.
4. Remove washer and capscrew.
5. Apply a light coat of oil to idler gear shaft. Position idler gear on idler shaft making certain timing
marks on idler gear are lined up with the crankshaft and camshaft timing marks. Install flat
washer and capscrew. DO NOT USE A CAPSCREW THAT IS LONGER THAN 75mm (2.95
inches).
S..amrhrftruambly, inrt.llrtlon, md tlming procedure for
complete gear tnin timlng Inrtructlonr.

Backplate
The gearcase backplate is made of cast iron and
supports the gears and gear cover. The backplate
also provides a mounting surface for the fuel injection pump and oil pump. The backplate is secured to
cylinder block by three capscrews and two socket
head screws located under large idler gear. The
backplate is sealed to cylinder block with a backplate
gasket.

Removal, I n a ~ t l o nand
, Installetlon:
1. Drain crankcase oil and remove oil pan and oil
pick-up tube. Refer to SECTION8, OIL SYSTEM.
2. Remove cylinder head, tappets, and gearcase
cover. Refer to Cylinder Head and Gearcase
Cover Removal procedures.
3. Remove fuel injection pump, mechanical fuel
transfer pump, and push rod. Refer to SECTION
10, FUEL SYSTEM for removal procedures.
4. Remove camshaft and large idler gear.

CRANKSHAFT FRONT OIL SEAL
AND WEAR SLEEVE
The crankshaft front oil seal is located in gearcase
cover. The lip-type seal fits tight on crankshaft or
wear sleeve. The outer diameter is tight in gearcase
cover. A front seal wear sleeve is available for servicing a damaged or seal grooved crankshaft.

Seal Removal
1. Remove gearcase cover as described in preced-

ing paragraphs.
2. Support gearcase cover and drive old seal out
from the back side of cover.
3. Clean opening in cover to receive a new seal.

Wear Sleeve Removal and Installation
1. Inspect wear sleeve or crankshaft for nicks, burrs,
and wear grooves. Replace or install a wear
sleeve if necessary.
2. If wear sleeve replacement is required, use a
hammer and a chisel, that is only as wide as the
wear sleeve, to make one or two chisel marks
across wear sleeve about three-quarters of the
way through. This will expand wear sleeve allowing for removal from crankshaft.

Do not nlck or gouge crankshaft wlth chkel. If crankshaft
is damaged It must be removed and mp8lred or
replaced.
3. Apply Loctite number 271 to crankshaft and
inside of new wear sleeve before installing.
Position wear sleeve on crankshaft with outside
chamfer toward front of engine.

Seal Installation
The outside diameter of front oil seal has a layer of
colored sealant which forms a seal between the seal
and seal bore in cover. This eliminates the need for
using a sealing compound before pressing a new seal
into cover. The inside diameter of oil seal has a lip
made from a rubber compound to prevent oil leakage
between seal and crankshaft or wear sleeve.
1. Place cover on a solid surface so back of seal bore

is supported.
2. Position seal in cover with open side of seal facing inside of cover and positioned squarely in
bore of cover.
3. Drive or press seal into cover bore until it bottoms
on shoulder, using the front wear sleeve-oil seal
installing tool and arbor press as illustrated in
Figure 37.
A new seal must be installed
with 8 new w a r Sleeve. The
seal should not be posltloned In a wear groove on
the crankshaft. Poirltlonlng a seal on a worn,
dlrty, rough, or grooved crankshaft surface wlll
cause the $881 to leak.

Make certain the seal seats
/
squarely on shoulder In cover
born. A seal that k cocked In bore wlll leak.
SEAL
OPlVER

4. Using front wear sleeve installing tool, pull wear
sleeve onto crankshaft. Tighten bolt until tool
bottoms on crankshaft.

5. Clean any surplus Loctite off wear sleeve and
crankshaft.

FIGURE 37. GEAR COVER OIL SEAL INSTALLATION

5. Remove the 'three capscrews and two socket
head screws from backplate (Figure 38).

SOCKETHEAD SCREWS

CAPSCRMS

FIGURE 38. BACKPLATE MOUNTlNG SCREWS

6. Gently work backplate off alignment pins and
idler gear shaft.
7. Inspect backplate for cracks, damage or wear,
and replace if necessary.
8. Use a new gasket for the installation and install
backplate by reversing the removal procedure.
Refer to Figure 38 for the location of capscrews
and socket head screws. After installing oil pickup assembly, make certain that oil pump turns
freely. If the oil pick-up mounting screws are
improperly tightened they will prevent oil pump
from turning. Refer to SECTION 8, OIL SYSTEM
for correct installation procedure.
9. Install fuel injection pump. Refer to SECTION 10.
FUEL SYSTEMfor correct installation and timing
procedures.

CRANKSHAFT
The cast nodular iron dynamically balanced crankshaft is carefully cast and machined to assure the
best possible strength and durability.
The crankshaft Is a very strong but

!ACAUTK)N 1 fragile prt of the engIne. Do not
scratch, dent or drop the crankshaft, dolng so may
cause severe damage to crankshaft bearing journah.
The bearing journals are not hardened and are easily
damaged.

Crankshaft end play is taken up by thrust flanges on
the rear main bearing. The crankshaft is drilled for
pressure lubrication from the main bearings to the
connecting rod bearings.

Removal
1. Remove oil filter and drain oil pan. Remove oil

3.
4.

pan and oil pick-up tube. Refer to SECTION 8,
OIL SYSTEM.
Disconnect wiring and remove starter. Remove
flywheel and flywheel housing. Refer to Flywheel
Housing Removal procedure.
Remove cylinder head assembly. Refer to the
Cylinder Head Removal procedure.
Remove tappets and camshaft. Refer to the
Tappet and Camshaft Removal procedures.
Remove gearcase cover and backplate. Refer to
the Gearcase Cover and Backplate Removal
procedures.
Remove connecting rod bearing caps, connecting rod bearing shells, and piston assemblies.
Refer to Piston Removal and Disassembly
procedure.
Mark bearing shells, tonnoctin~rodr, and rodaps as to their
original location in the cylinder Mock.

7. Remove main bearing caps and lower main bearing shells.
8. Remove crankshaft. Some crankshaft rotation
may be necessary during removal.
9. Remove upper main bearing shells from cylinder
block.

Inspection and Repair
Clean crankshaft thoroughly and inspect journals for
scoring, chipping, cracking, or signs of overheating.
If crankshaft has overheated, is scored, or excessively worn, reconditioning or replacement will be
required. Examine bearing journal9 for cracks if
overheating has occurred.
Measure crankshaft main bearing and connecting
rod journals at several places on their diameter to
check for roundness and taper. If out-of-round or
taper of journals exceeds .005mm (.0002 inch),
crankshaft must be reground or replaced.
Due to the method of grinding and fillet rolling of the
turbocharged engine crankshaft, Onan recommends
that the crankshaft not be ground and used again in
turbocharged engines. Regrinding of a turbocharged
engine crankshaft for use in a naturally aspirated
engine is acceptable.
The only recommended method of reconditioning
the crankshaft is regrinding, as required to accommodate undersize bearings. Metallizing of bearing
journals is not recommended.
..
If regrinding of crankshaft journals is necessary, the
work should be done by a reputable machine shop
that has suitable equipment to handle precision work
of this type. Undersize main bearing shells are available in sizes of 0.25mm, O.SOmm, 0.75mm and 1.00mm.
Clean out all oil passages in crankshaft after regrinding.

Installation
Make certain bearing seats and bearing shells (front
and back) are clean and free from dirt and grit
particles.
1. The upper main bearing halves are marked
FRONT UPPER. INTER. UPPER. CTR. UPPER,
and UPPER REAR. Position the upper main bearing shells in their appropriate location making
certain bearing tang is in slot of bearing seat in
cylinder block. The rear main bearing shell has a
saddle type thrust surface. This thrust surface
controls crankshaft endplay.
2. Lubricate all crankshaft bearing journals with oil.
Lower crankshaft into position. Some crankshaft
rotation may be necessary to miss the casting
bosses i n crankcase. Make certain flywheel
flange end of crankshaft is toward the rear.
3. The bearing caps are numbered 1,2.3; etc., indicating their respective positions in block. The
front and rear bearing caps are also marked F and
R respectively.

CRANKSHAFT GEAR
The crankshaft gear may be removed from crankshaft
by using a gear separator and puller. See Figure 41.
Gear may be removed either with crankshaft installed
(backplate removed) or after crankshaft has been
removed from engine.

GEAR PULLER

RANKSHAFT
GEAR

To install crankshaft gear on crankshaft, install
woodruff key in crankshaft. Heat gear on an electric
burner or oven to about 175' C (350° F). Drive or press
gear onto crankshaft. Timing marks must be visible
from front end of the crankshaft.

When handling the heated gear,
@
!
!
@
m%
r asbe8tor
I glove8 to prevent
bums.

FIGURE 41. CRANKSHAFT GEAR REMOVAL

4. The lower main bearing halves are marked

LOWER FRONT, LOWER INTR & CTR, and
LOWER REAR.
Position the lower bearing shells in the appropriate bearing cap. Make sure bearing tang is
seated in slot of bearing cap. Lubricate bearing
shells with clean engine oil.
5. lnstall main bearing caps with raised arrow facing
camshaft side of engine starting with number one
at front of engine (Figure 39). Push crankshaft
toward front of engine, this will bring rear bearing
thrust surfaces into alignment.

ARROW
TOWARD
CAMSHAFT

The crankshaft must turn freely after all capscrews are properly torqued. Never file or shim a
bearing cap to make the bearing shell fit. Install
new bearing shells if the fit on crankshaft is unsatisfactory. Refer to SECTION 2, DIMENSIONS
A NO CLEARANCES for clearance specifications.
7. Check crankshaft endplay using a dial indicator
(Figure 40). Push the crankshaft in one direction
to take up endplay. After dial indicator is set to
zero and in place, pull crankshaft in opposite
direction to obtain endplay reading. Endplay is
controlled by thrust flanges on rear main bearing.
If endplay is not within specification, replace rear
main bearing.

FIGURE 39. MAIN BEARING CAPS

6. lnstall main bearing capscrews and washers.
Using a torque wrench, alternately and in steps
tighten capscrews evenly to a torque of 123 Nm
(90 Ft.-Lb.).

Do not over-toque main imaring
I
capscrews. n these capscrews are
over-tightened,bearjng caps may be distorted, causing bearings to 6e drawn tight against crankshaft
which can result in premature bearing fsilure.

8. Install piston assemblies, connect~ngrod bear~ng
caps, and bearing shells.
9. Complete installation by reversing the removal
procedure.

MAIN BEARINGS
The precision main bearings are replaceable without
machining. Rear main bearing has two thrust flanges.
These flanges control crankshaft endplay. All standard main bearings have an inside diameter of
76.040mm to 76.090mm (2.9937 inch to 2.9957 inch)
when installed with bearing caps properly torqued.
The upper halves of main bearing shells are seated in
lower part of cylinder block. The lower halves of main
bearing shells are held in place by main bearing caps,
which are secured to cylinder block by capscrews.
The bearing shell is positioned by a tang in the shell
that locates in a slot in bearing seat of cylinder block
and bearing cap. The upper front bearing shell has
two oil holes in it. The other upper bearings have only
one oil hole. Lower bearing shells do not have any oil
holes and are installed in the bearing caps.

Removal
1. Remove crankshaft. Refer to Crankshaft Removal
procedure. Identify bearing shells as to their original location in main bearing caps and cylinder
block in the event bearing inspection proves they
can be reused.
2. Remove upper bearing shells from their seats in
cylinder block.
3. Remove lower bearing shells from their seats in
main bearing caps.

Inspection
Any bearing shell that is scored, chipped, pitted or
worn beyond the specified limits must be replaced.
Inspect backs of shells for bright spots. Bright spots
on the backs of shells indicate shells have moved in
their supports and are not fit for further use. With
crankshaft removed, bearing cap installed and tightened to the specified torque, measure inside diameter of bearing at a point 90' from the parting line. The
shells havea pressure fit in their bore in the block and
must be tight when bearing cap is secured in place.
Do not measure inside diameter at bearing parting
line.

lnstallation
Make certain bearing seats and bearing shells (front
and back) are clean and free from dirt and grit
particles.
1. Place a main bearing shell in each bearing seat in
cylinder block. Makecertain tang of bearing shell
is properly seated in bearing seat recess. See
Crankshaft lnstallation procedure for correct
bearing locations.
2. Lubricate all crankshaft main bearings and
crankshaft journals.
3. Install main bearing caps and bearing shells.
Check crankshaft endplay and reassemble
engine. Refer to Crankshaft Installation procedure.

Main Bearing Replacement With Crankshaft
Installed
It is unwise to replace main bearings without removing thecrankshaft. If removal of crankshaft is impractical or in emergency cases, the following procedure
may be used.
1. Remove glow plugs. This will relieve compression and allow free turning of the crankshaft.
2. Drain crankcase oil and remove oil pan and oil
pick-up tube. See SECTION 8, OIL SYSTEM.
3. Remove only one bearing cap at a time. Install
new bearing shells and reinstall bearing cap
before removing the next bearing cap.
4. Lower bearing shell can be removed from bearing
cap and replaced after cap is removed from
engine.
5. Remove upper bearing shells as follows:
A. Insert a cotter pin with head flattened, into
crankshaft main bearing oil hole (Figure 42).

The inside diameter of installed new standard main
bearings is 76.040mm to 76.090mm (2.9937 inch to
2.9957 inch) and any measurement above 76.090mm
(2.9957 inch) indicates the amount of bearing wear.
Measure diameter of crankshaft journal at the corresponding bearing location and subtract this
dimension from inside diameter measurement of
bearing as measured above. The difference between
these two measurements is the crankshaft to bearing
clearance.
The specified clearance between main bearing shells
and crankshaft journal is .03mm to .10mm (.0012 inch
to .0039 inch).

FIGURE 4 2 REMOVING UPPER MAlN BEARING SHELL

1
!

Rotate crankshaft in direction that will remove tang end of bearing shell first. Continue
rotating crankshaft until bearing shell has
been pushed all the way out.
C. One of the center main journals will not have
an oil hole in it. Use a narrow brass bar to push
this upper bearing shell out.
6. Inspect crankshaft journalsforscoring, chipping,
cracking, or signs of overheating. Remove and
regrind or replace crankshaft if it is worn or has
overheated.
7. Replace any bearing shell that is scored, chipped,
pitted, or worn beyond the specified limits.
8. Install upper bearing shell by lubricating shell
with clean oil. Roll shell around crankshaft journai in the opposite direction that it was removed
until tang on bearing shell is positioned in
cylinder block recess.

1-1

00 not scratch bearing back
when rolling bearing in. Be sun

bearing r o k in tree.

9. Place a lower bearing shell in bearing cap. Bearing caps are numbered 1,2,3, etc., indicating their
respective positions in cylinder block. Front and
rear bearing caps are also marked F and R
respectively.
10. Lubricate bearing shell and place bearing cap in
position on cylinder block with raised arrow fating camshaft side of engine.
11. lnstall main bearing capscrews and washers.
12. Use a torque wrench to alternately tighten capscrew evenly to a torque of 123 Nm (90 Ft.-Lb.).

Do not over-bque main bearing
~ a p s c r m If. them capscmm a n
over-tightened, b e a m Cam may k distorted,CaU8ing bearings to be dmwn tight against cmnkrhatt
which can resuit in premature bearing hllum.

/BCAUTION

13. Check bearing clearance with Plastigage. Refer
to Checking Bearing Clearance with Plastigage
for correct procedure.
14. Check crankshaft end play. Refer to Crankshaft
Installation procedure.
15. lnstall oil pick-up tubaand oil pan. Refill crankcase with clean oil.
16. lnstall glow plugs.

Checking Bearing Clearance With Plastigage
The most accurate means of determining bearing
clearance is by using micrometers. However, if
crankshaft is installed in engine, bearing clearance
may be measured by using a plastic strip (Plastigage)
manufactured for this purpose.
1. Using a clean, dry rag, thoroughly clean all oil
from crankshaft journal and bearing shell. Place a
piece of the correct size Plastigage the full width
of crankshaft journal surface about 7mm (.2500
inch) off center.
2. lnstall bearing cap with bearing shell and tighten
boltsor nuts to the specified torque. Do not rotate
crankshaft.
3. Remove bearing cap. The flattened Plastigage
will be found adhering to either the bearing shell
or crankshaft.
4. Compare flattened Plastigage with the graduations on Plastigageenvelopeto determineclearance.
The number within the matching graduation on
theenvelope indicates, total clearance in millimetres or thousandths of an inch.

CYLINDER BLOCK
The cylinder block is the main support for all other
basic engine parts. The block is a one piece casting
made from cast iron. Transverse end walls and center
webs are cast in the block to support the crankshaft
and camshaft, assuring alignment of crankshaft and
cylinders. Cylinder bores are completely surrounded
by water jackets which extend the full length of the
cylinder walls for maximum cooling.

Cleaning
After removing pistons, crankshaft, cylinder head,
etc., inspect block for cracks and extreme wear. If
block is still serviceable, prepare it for cleaning as
follows:
1. Scrape all old gasket material from block.
Remove all oil galley plugs to allow cleaning solution to contact inside of oil passages.
2. Remove grease and scale from cylinder block by
agitating in a bath of commercial cleaning solution or hot soapy washing solution.
3. Rinse block in clean hot water to remove cleaning
solution.
4. Be sure to clean and dry all water passages, oil
passages, and drilled holes.

5. Coat pipe threads with teflon pipe sealant.
Replace all pipe plugs removed for cleaning of oil
passages. Install new freeze plugs as required
using green Loctite RC/601 to seal plugs.

Inspection
When rebuilding the engine, thoroughly inspect
block for any condition that would make it unfit for
further use. This inspection must be made after all
parts have been removed and block has been thoroughly cleaned and dried.
1. Makea thorough check for cracks. Minutecracks

may be detected by coating the suspected area
with a mixture of 25 percent kerosene and 75
percent light motor oil. Wipe the part dry and
immediately apply a coating of zinc oxide (white
lead) dissolved in wood alcohol. If cracks are
present, the white coating will become discolored
at the defective area. Always replace a cracked
cylinder block.
2. Check all dowel pins, oil galley plugs, and freeze
plugs for wear or damageand replace as necessary.
3. Inspect all machined surfaces and threaded
holes. Carefully remove any nickqor burrs from
machined surfaces. Clean out tapped holes and
clean up any damaged threads.
4. Check top of block for flatness with a straight
edge and a feeler gauge (Figure 43). This surface
is the critical area for sealing oil, water and compression. If warped, a maximum of .05mm (.002
inch) may be machined from top of cylinder
block. If warpage exceeds .05mm (.002 inch)
replace block.

FIGURE 43. CHECKING TOP OF
CYLINDER BLOCK FOR FLATNESS

Cylinder Bore I n s ~ t l o n Inspect
:
cylinder bores for
scuffing, scratches, wear, and scoring. If cylinder
bores are scuffed, scratched, scored, or worn, they
must be rebored and honed for the next oversize
piston. Main bearing caps must be installed and
properly torqued, before measuring cylinder bore.
When the appearance of cylinder bores is good and
there are no scuff marks, check cylinder bore for wear
or out of roundness as follows:
1. Check cylinder bore for taper, out of round and

wear, with a cylinder bore gauge, telescope
gauge or inside micrometer. These measurements should be taken at four places, top and
bottom of piston ring travel, parallel and perpendicular to axis of crankshaft.
2. Record measurements taken lengthwise at top
and bottom of piston travel as follows (see Figure
44) :
A. Lengthwise of block, measure and record as
"A" the diameter of cylinder at the top of
cylinder where greatest ring wear occurs.
8. Also. lengthwise of block, measure and
record as "6" the cylinder diameter at the
bottom of piston travel.
C. Crosswise of block, measure and record as
"C" the diameter of the top of cylinder at the
greatest point of wear.
D. Measure and record as "D" the diameter at
bottom of cylinder bore and crosswise of
block.
E. Reading " A subtracted from reading "8"and
reading "C" subtracted from reading "D"
indicates cylinder taper.

F. If cylinder taper exceeds 0.076mm (0.003
inch) rebore and hone to accommodate the
next oversize piston. Reading "A" compared
to reading "C" and reading "8" compared to
reading "D" indicates whether or not cylinder
is out of round. If out of round exceeds
0.025mm (0.001 inch), the cylinders must be
rebored and honed for the next oversize piston. Oversize pistons and rings are available
in 0.25mm. O.5Omm. 0.75mm, and 1.00mm.

Reboring the Cyllnder
Before boring or honing cylinder bores, all main
bearing caps must be properly installed and torqued.
Rebore and hone engine whenever cylinder bore is
worn, damaged, out of round or if cylinder taper
exceeds specifications. A worn cylinder bore should
be resized to the smallest standard oversizediameter
at which it will clean up. The final finish and bore
diameters should then be obtained by honing.

I-[

Ilborlng lmrk op.ntod/ncomcfly,
It Wll l p r o 8 rough cylinder
8urhce tbat m y not c h n up even when honod.
Borlng 8houM k dorm only by qwlltled 8onlc.
personnel who am camfu/ In thelr work.

TOP END OF CYLINDER

After boring to the correct oversize cylinder bore
dimension piston and ring clearance should be
appropriate. There is no need to adjust or "fit" pistons
and rings.
When reboring cylinders, take the following precautions:

C-10S2

BOTTOM OF RING TRAVEL

1. Make sure cutting tool is properly ground before
using it.
2. Be sure top of engine block is smooth and deposit
free.
3. Clean base of boring bar before bar is set up.
Deposits under boring bar will cause it to tilt and
the cylinder will be distorted after boring.
4. Makean initial rough cut, followed by afinish cut.
Then hone cylinder bore to the specified
oversize.

Honing Cylinders (Using Precision Hones)
The L engine is a high speed, high output diesel which
requires a quality surface finish forthe engine's pistons
and rings. This finish can best be provided by using two
stage honingwith quality equipment intended for honing
engine cylinder bores.
The following honing procedure providesa good quality
finish that allows maximum engine life and good oil
control.
1. Honing Machine Tool Set Up:

A. Honing rotational speed 170 rpm.

8. Honing stroke length - 142mm45.6) with 3.5"
stones. This providesabout30mm of overstroke
a?BQththe top and bottom ofthe cylinder bore.
Watch for interference between the honing
head and, the main bearing bore bulkheads
during set up.

. -

FIGURE 44. ,METHODS OF MEASURING WE
DIAMETER OF A CYLINDER BORE

C. For first stage h-g,
or rough honing, use a
soft (fast cutting) 150 grit silicon carbide stone.

D. For second stage honing, or finish honing, use a
medium hardness400 grit silicon carbide stone.

2. Honing Procedure:

Deglazing Cylinder Bores

A. Hone the cylinders to their final size during the
rough honing stage. If the cylinder block is
bored to an oversize before honing, .05 to
.13mm (.002 to .005") of material should be left
after boring for clean up during the honing
operation.

Deglaze the cylinder bores ifthere are no scuff marks
and no wear or out of round beyond specifications
before installing new rings. Deglazing gives a fine
finish, but does not enlarge cylinder diameter, so the
original pistons with new rings may still be used.

B. Check diameter of the cylinder bore regularly
during honing. A dial bore gauge is the easiest
method but a telescoping gauge can be used.
Check size at six places in the bore, measuring
twice at the top, middle and bottom 90 degree
apart.

The reason for deglazing a cylinder is to provide
cavities to hold oil during piston ring break-in.

C. Finish hone by installing the finishing stones
into the cylinder and expanding until snug. Then
hone for 15 to 20 additional strokes at a medium
to low feed rate.
D. Clem the cylinder bores thoroughly with soap,
water and clean rags. A clean white rag should
not be soiled on the walls after cleaning is
complete. Do not use solvent or gasoline since
they wash oil from the walls and leave the metal
particles.

1. Wipe cylinder bores with a clean cloth which has
been dipped in clean, light engine oil.
2. Use a brush type deglazing tool with coated bristle tips to produce a crosshatch pattern in the
cylinder bore.
3. The deglazing tool should be driven by a slow
speed drill. Move deglazing tool up and down in
cylinder (10 to 12 complete strokes) rapidly
enough to obtain a crosshatch pattern as shown
in Figure 46.

E. Dry the crankcase and coat it with oil.
3. Honing Results:
A. The recommended honing cross hatch pattern
12 degrees
is an included angle of 56
(Figure 45) when measured perpendicular to
the cylinder bore axis.

8. Surface finish of the completed cylinder bores
should range from .4 to 1.0 um Ra.

PRODUCECROSSHATCHSCRATCHES
FOR FAST RING SEATING

AVOID THIS FINISH
C-1015

FIGURE 46. CROSS HATCHlNG

4. Clean cylinder bore thoroughly with soap, water
and clean rags. Keep on cleaning until a clean
white rag shows no discoloring when wiped
through cylinder bore.

Never we garollne or commer-

IPCAUTK)(3 1/81 cleaner8 to c l a n cylinder

bore8 after degMng or honlng. These solvents
will not mmove abrasive8 from the walls. Abra8Ive8 not removed from englne will rapidly wear
rlngs, cylinder mllr, and baatfng rurfsces of all
lubdcated pnrtr.
FIGURE 45. CROSS HATCH ANGLE (MAGNIFIED)

Turbocharger
SUBJECT

PAGE

Turbocharger ..........................................................14-1
Removal .............................................................14-1
Inspection ...........................................................14-2
Installation ...........................................................1 4 4

TURBOCHARGER,
A turbocharger is used to boost the power output of
an engine over that of a naturally aspirated engine by
increasingtheamount of air supplied to the cylinders.
The turbocharger uses engine exhaust gases to drive
a turbine wheel mounted on a common shaft with a
radial air compressor impeller.

REMOVAL
Chonextorlor oIen111, turbocharger
/
auembIyyair Intake plplng, and 011
/In08 to pnwonf the mttanco of fonlgn mterlal Into
engin0 8nd turbocharger durlng removal.

1. Remove air intake piping from turbocharger

compressor housing inlet and outlet.
The turbocharger feeds denser compressed air
directly into theengine intake. Thisallowstheengine
to burn fuel more efficiently and to deliver more
power per stroke from a given engine capacity.

On some turbochargers a turbine bypass valve or
wastegate is used to control boost. Wastegate
operation is controlled by an actuator that senses
compressor discharge pressure and balances it
against a preset spring load. The wastegate valve
located in the turbine inlet passage diverts a portion
of the exhaust gas away from the turbine wheel to
control shaft speed and compressor air output.

2. Remove exhaust pipe from turbocharger.
3. Disconnect oil lines from turbocharger. Cover all
openings to prevent the entrance of dirt and
foreign material.
4. Remove hex nuts that secure turbocharger to
exhaust manifold.

5. Remove turbocharger and gasket from exhaust
manifold.
6. After removal, using a vice, secure turbocharger
at turbine inlet flange.

INSPECTION

To check radial play compressor, housing must be
removed.

General inspection can be done without removing
turbocharger. Inspect turbine wheel and compressor
impeller for cracks, erosion, nicked or bent blade tips,
and broken or missing blades. Inspect housings for
rubbing, scoring, and erosion. If turbocharger damage
or wear is evident, replacement or further disassembly
and repair is necessary.
Check for oil in exhaust outlet and turbo-to-intake
manifold piping. If oil is present it indicates a
restriction in air intake system or a turbocharger seal
failure. Remove any restriciton found in intake system.
If no restriction is found remove turbocharger for
replacement or repair.
Check for free rotation of the turbine wheel and
compressor impeller. If wheel and impeller do not
rotate freely, parts may be damaged, or foreign
material may be causing friction, in which instance
replacement or further disassembly and inspection is
necessary.

1. Mark relative position of compressor diffuser and

compressor housing.

Urn care to prevent damage to
rotatlng part8 of the turbocharger;avold rough handling. A turbochargerh
a pmcl$lon built p l ~ of
e equipment. Do not pry
on rotaf/ng components or $et turbocharger on
turbine wheel or compreuor impelhr.
2. Remove capscrews and clamping plates that
secure compressor housing to compressor diffuser. Lift off compressor housing.
3. Mount dial indicator on compressor impeller hub.
4. Check shaft radial play by pushing impeller

towards and away from shaft centerline. Total
radial play should be within 0.30 mm to 0.46 mm
(0.012 inch to 0.018 inch).

If no damage or excessive friction is detected, check
end (axial) play and radial play with a dial indicator.

5. Install compressor housing, checking the scribe
marks for proper alignment.

Holret Bearing Clearance Inspection

6. Install clamping plates and capscrews. Torque
compressor housing capscrews to 5.7 Nm(4 Ft.-Lb.).

Mount dial indicator on end of turbocharger shaft.
Push shaft in one direction to take up end play. Set
dial indicator to zero and pull shaft in opposite
direction to obtain end play reaching. Total end-play
reading should'be0.10 mm to0.16 mm (0.004 inch to
0.006 inch).

If end play and radial play are within the limits
specified, turbocharger bearings and internal components are within limits.
Removeturbocharger for replacement or repair if end
play or radial play are not within the limits.

TURBOCHARGER
ASSEMBLY

BOLT

RING

Aimsearch Bearing Clearance Inspaction
With turbocharger removed from the engine, check
journal bearings for radial clearance as follows:

Check thrust bearingfor end play (axial) clearanceas
follows:

1. Remove retainingring (Figure 2) and slip actuator
rod eye off wastegate lever pin.

1. Position a dial indicator on turbocharger so that
the indicator arm rests on end of turbine wheel
assembly.

2. Remove capscrews, elbow assembly, and gasket
from turbocharger.

2. Manually move compressor wheel and turbine
wheel assembly as far away as it will go from the
dial indicator arm. Set dial indicator to zero.

3. Position a dial indicator on turbocharger so that
the indicator arm extends through oil outlet port
and contacts turbine wheel assembly shaft.

4. Manually apply pressure to the compressor and
turbine wheels to move the shaft as far away as it
will go from the dial indicator arm. Set dial
indicator to zero.

5. Manually push compressor and turbine wheels
toward dial indicator arm. Record the maximum
shaft movement shown on indicator dial.

To make sure the dial indicator reading is correct,
roll the wheels slightly in both directions while
applying pressure.

6. Manually apply pressure to the compressor and
turbine wheels to move the shaft as far away as it
will go from the dial indicator arm. The dial
indicator should return to zero.

7. Repeat Steps 4, 5, and 6 several times to verify
that the maximum bearing radial clearance has
been measured.

8. If the maximum bearing radial clearance is less
than 0.08 mm (0.003 inch) or greater than 0.15 mm
(0.006 inch), replace turbocharger or have it
repaired.

3. Manually move compressor wheel and turbine
wheel assembly as far as it will go toward the dial
indicator arm. Record the maximum shaft movement shown on indicator dial.

4. Manually move compressor wheel and turbine
wheel asembly away from dial indicator arm. The
dial indicator should return to zero.

5. Repeat Steps 2, 3, and 4 several times to verify
that the maximum bearing end play clearance has
been measured.

6. If the maximum bearing end play (axial) clearance
is less than 0.03 mm (0.001 inch) or greater than
0.08 mm (0.003 inch), replace turbocharger or
have it repaired.

INSTALLATION
Never replace a turbocharger without first establishing the reasons for any previous failure.
1. Inspect air intake system and exhaust manifold

8. Connect compressor inlet and outlet piping.
Connect exhaust piping. Check all joints for
possible leaks. Make certain that piping is not
placing any strain on torbocharger.

for foreign material and cleanliness.
2. lnspect oil drain line. Make certain line is not
blocked.

9. Crank engine without firing until a steady flow of
oil is coming out of oil drain line.
to. Stop cranking and connect oil drain line to

3. lnspect oil supply line for restrictions, deterioration, or leaks.
4. Clean turbocharger mounting flange surface and
mounting surface on exhaust manifold to make
certain that all of the old gasket has been removed.

5. Position new gasket on exhaust manifold. Gasket
should not protrude into manifold opening.
6. Install turbocharger on manifold. Secure with
flatwashers and hex nuts. Torque hex nuts to
52 Nm (39 Ft.-Lb.).
7. Connect oil supply line. Connect oil drain line to
turbocharger. Leave oil drain line disconnected
at cylinder block at this time.

cylinder block.

Contact with rotating machinery
AWARNING can
I
cause serious personal injury or death. Stay clear of rotating components
and ensure that air intake piping, air cleaner, and
exhaust pipe are in place and secured before
operating engine.

1-1

Fomlgn object8 may be drawn
Into turbocharger If air Intake
plplng and alr cleaner are not In place. Forelgn
oblectt entering the turbocharger can came
srlous turbocharger or engine damage.

Onan Corporation
1400 73rd Avenue N.E.
Minneapolis. MN 55432 (612) 574-5000

Telex 29 0476 (U.S.)
Telex 29 0856 (outside US.)
TWX 91o 576-2833
Cable ONAN

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Onan L Series L423 Engine Service Manual

934-0750 Onan L series (L317 L423 L634 L634T) Diesel Engine Service manual (06-1986) 934-0750 Onan L series (L317 L423 L634 L634T) Diesel Engine Service manual (06-1986)

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