Onan RDJC, RDJF Service Manual

Service

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Manual

Diesel

Engines

9-84

Printed

in

USA.

Safety

Redistribution or publication of this document, 

by any means, is strictly prohibited.

It

is recommended that you read your engine manual and

Precautions

become thoroughly acquainted with your equipment be-

fore you start the engine.

This symbolls used throughout this

of

manual to warn

posslble serious

personal Injury.

DO

NOT

smoke or use an open flame in the vicinity of
the engine or fuel tank. Internal combustion engine
fuels are highly flammable.

Fuel lines must be of steel piping, adequately secured,
and free from leaks. Piping at the engine should be

Do

approved flexible line.

not use copper piping for
flexible lines as copper will work harden and become
brittle enough to break.

.I

Thls symbol

refers

to posslble equip-

ment damage.

Fuels, electrical equipment, batteries, exhaust gases and
moving parts present potential hazards that could result in
serious, personal injury. Take care in following these
recommended procedures.

Safety Codes

0

All local, state and federal codes should be consulted
and complied with.

0

This engine is not designed or intended for use in
aircraft. Any such use is at the owner's sole risk.

General

Provide appropriate fire extinguishers and install them
in convenient locations. Use an extinguisher rated ABC
by NFPA.

Make sure that all fasteners on the engine are secure
and accurately torqued. Keep guards in position over
fans, driving belts,. etc.

it

is necessary to make adjustments while the engine is

If
running, use extreme caution when close to hot ex­hausts, moving parts, etc.

Protect Against Moving Parts

Do

not wear loose clothing in the vicinity of moving
parts, such as PTO shafts, flywheels, b'lowers, coup­lings, fans, belts, etc.

Keep your hands away from moving parts.

Batteries

0

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

DO

NOT SMOKE while servicing batteries. Lead acid

of

the engine.

batteriesgive offa highlyexplosive hydrogen gas which

can be ignited by flame, electrical arcing or bysmoking.
Verify battery polarity before connecting battery cables.

Connect negative cable last.

Fuel System

DO

NOT fill fuel tanks while engine is running.

Be sure all fuel supplies have a positive shutoff valve.

Exhaust System

Exhaust products of any internal combustion engine
are toxic andscan 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.

0

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 is Deadly!

Exhaust gases contain carbon monoxide, a poisonous gas
that might cause unconsciousness and death. It is an
odorless and colorless gas formed during combustion of
hydrocarbon fuels. Symptoms of carbon monoxide poi­soning are:

0

Dizziness
Headache
Weakness and Sleepiness

'Vomiting

0

Muscular Twitching

0

Throbbing in Temples

If you experience any 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

it

immediately and have

inspected and repaired at once bya

competent mechanic.

'Cooling System

Coolants under pressure have a higher boiling point

DO

than water.

NOT open a radiator pressure cap when
coolant temperature is above 212°F (100OC) or while
engine is running.

Keep

the Unit and Surrounding Area Clean

Make sure that oily rags are not left on or near the
engine.

Remove all unnecessary grease and oil from the unit.
Accumulated grease and oil can cause overheating and

a

subsequent engine damage and present

potential fire

hazard.

n

.

E-4

.

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Table

of

Contents

TITLE

General Information
Specifications

Dimensions and Clearances
Assembly Torques and Special Tools
Engine Troubleshooting

Service and Maintenance ...............................................

Exhaust System
Cooling System
Fuel System
Oil System
Governor System
Starting System
Engine Disassembly
Control System

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

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

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

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

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

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

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

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

....................................................... 16

..................................................... 39

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

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

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

PAGE

2

3

4.
6

7

8

14

22

36

41

48

59

INCORRECT SERVICE
SEVERE PERSONNAL INJURY AND/OR EQUIPMENT DAMAGE
PERSONNEL MUST BE QUALIFIED
MECHA NlCA L SERVICE

OR

REPLACEMENT OF PARTS MIGHT RESULT IN

.

SERVICE

TO

PERFORM ELECTRICAL AND/OR

.

1

General Information

Redistribution or publication of this document, 

by any means, is strictly prohibited.

INTRODUCTION

This manual deals with specific mechanical and elec­trical information needed by engine mechanics for
troubleshooting, servi,cing, repairing, or overhauling
the engine.

Use the table of contents for a quick reference to the

separate engine system sections.

Use the separate parts catalogs, available at the
dealer level, for parts identification and for establish­ing their proper location on assemblies.

The troubleshooting guide is provided as a quick

reference for locating and correcting engine trouble.

The illustrations and procedures presented in each
section apply to the engines listed on the cover. The
flywheel end of the engine is the front end,
and left sides are determined by viewing the engine
from the front.

The disassembly section contains major overhaul

procedures for step by step removal, disassembly,
inspection, repair, and assembly of the engine

components.

so

right

ENGINE

Identify your model by referring to the MODEL and

SPEC (specification)

nameplate. Always use this number and the engine

serial number when making reference to your engine.
How to interpret

set engines.

1.

Factory code for general identification purposes.

2.

Specific TYPE, as follows.

R

E

3.

Factory code for specific optional equipment

supplied.

4.

Specification (Spec Letter). Advances with fac­tory production modifications.

MODEL

-

REMOTE type. Electric starting. Optional
accessory equipment can be connected for
wire remote control of starting and stopping.
A two

(2)

is available for standby service.

-

ELECTRIC start type. Electric starting at the
plant only.

REFERENCE

NO.

as shown on the unit

MODEL

1

wire automatic line transfer control

and

2

SPEC

34

NO.

on generator

2

<

If a major repairpr an overhaul is necessary, a compe-

tent. mechanic should either do the job or supervise

and check the work of the mechanic assigned to
the job to ensure that all dimensions, clearances, and

torque values are within the specified tolerances.

The wiring diagram on the last page of the manual
shows how the electrical components are inter­connected.

A parts catalog (available at the dealer level) contains

detailed exploded views of each assembly, the indi­vidual piece part numbers, and their proper names,
for ordering replacement parts.

Use only Genuine Onan replacement parts to ensure

quality and the best possible repair and overhaul

results. When ordering parts, always use the com-

plete Model and Spec number as well as the Serial

number shown on the nameplate.

.

do

How to interpret

engines.

1.

Factory code for general identification purposes.

2.

Starter TYPE,
M-ELECTRIC start type.

S-MANUAL start type.

3.

PTO TYPE, as follows:

F

-

CLUTCH

A

-

STUB SHAFT

4.

Factory code for specific optional equipment
supplied.

5.

Specification (Spec Letter). Advances with fac­tory production modifications.

2

MODEL

1.

as

and

follows:

SPEC

NO.

on industrial

4.5

1

Specifications

Redistribution or publication of this document, 

by any means, is strictly prohibited.

~~ ~

All dimemsions in

~

SPECIFICATION MEASURE RDJC RDJF

Number

of

Cylinders 4 4

U.S.

customary units

of

measure (metric in parentheses) unless otherwise specified.

UNIT OF

SERIES

Diesel Fuel ASTM2-D ASTM2-D
Bore in 3.250 3.500

(82.55) (88.90)

3.625 3.625

Stroke

(mm)

in

(mm) (92.08) (92.08)

Displacement cu in 120 140

(litre) (2.0) (2.3)

Compression Ratio 19.0 to

1

19.0 to

1

Firing Order 1-2-4-3 1-2-4-3
Crankshaft Rotation

(viewed from flywheel) Clockwise Clockwise
Governor Adjustable Mechanical
Valve Clearance (Cold)

Intake in

(mm)

Exhaust

in

(mm)

0.01

1

0.01

7

(0.279) (0.432)

0.01 6 0.01

7

(0.406) (0.432)
Oil Filter Full Flow Full Flow
Crankcase Capacity Qt 6.5

with filter change

(litre) (6.15) (6.15)

6.5

Battery Requirements:.

Ambient Temp. Quantity

Range Required

32" F and

warmer 2

0"

F and

warmer

-25Oand
warmer

2

Voltage BCI Group Cranking Perf. Amp Hr Cap

Size (Amps) at 0°F

(20

Hr. Rate)

6 2 565 135

6 5D

800

1080

190

222

3

Dimensions and Clearances

Redistribution or publication of this document, 

by any means, is strictly prohibited.

All clearances given at room temperature

Ail dimensions in inches (mililmetres

CAMSHAFT

Bearing Journal Diameter. Front
Bearing Journal Diameter. Center
Bearing Journal Diameter. Rear
Bearing Clearance Limit
Bearing Clearance Limit (Replacement)

End Play
Cam Tappet.Diameter (RDJC Prior to Spec P)
Cam Tappet Hole Diameter (RDJC Prior to Spec P)
Cam Tappet Diameter (RDJF. RDJC Begin Spec P)
Cam Tappet Hole Diameter (RDJF. RDJC Begin Spec P)

CONNECTING

Large Bore Diameter
Small Bore Diameter
Large Bearing Bore to Small Bearing Bore

(Center-to-Center)

Connecting Rod End Play

CY

LlNDER

Bore Honed Diameter
Maximum Allowable Taper
Maximum Allowable Out-of-Round

CRANKSHAFT

Main Bearing Journal Diameter
Front and Rear Main Bearing Clearance (Original)

Center Main Bearing Clearance (Original)

Front and Rear Main Bearing Clearance (Replacement)
Center Main Bearing Clearance (Replacement)
Connecting Rod Journal Diameter
Rod Bearing Clearance
End Play

PISTONS AND RINGS

Clearance
Measure
Ring Groove Width

TOP

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

NO

.

2

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

NO

.

3

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

NO

.

4

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

Ring Gap

PISTON PIN

Clearance in Piston
Connecting Rod Bushing Clearance

STARTING MOTOR

Rotation
Pinion Clearance to Pinion Stop (Solenoid Plunger Bottomed)
Armature End Play

.

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

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

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

(0

rig i nal)

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

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

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

RODS

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

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

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

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

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

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

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

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

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

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

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

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

in

Cylinder

90"

to pin. just below oil ring

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

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

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

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

(Prestolite)

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

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

in

parentheses) unless otherwise specified .

..

.'

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

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

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

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

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

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

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

i

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

of

70' F (21'C)

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

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

.

2.2500-2.2505 (57.150-57.163)

I

.2580. 1.2582 (31.953-31.958)

1

.

1875-1 . I880 (30.1 63-30.1 75)

.0015-. 0030 (.038-.076)
.0012-. 0049 (.030-.123)

.007-. 039 (0.2-1.0)
.7475-. 7480 (18.987-18.999)
.7507.. 7515 (19.068-19.088)
.8725.. 8730 (22.162-22.174)
.8755-. 8765 (22.238-22.263)

2.1871-2.1876 (55.5523-55.5650)

1.043-1.045 (26.4922-26.543)

5.998-6.002 (1 52.3492-1 52.4508)
.002-. 016 (.05-.41)

3.2495-3.2505 (82.537-82.563)

:

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

2.2427-2.2435 (56.965-56.985)
.0030-. 0043 (.076-.109)
.0024-. 0052 (.061-.132)

.0024-. 0062 (.06-.16)

.0024-. 0052 (.061

2.0597-2.0605 (52.31 6-52.337)

.001-. 0033 (.025-.084)

.010-. 015 (.254-.381)

.0055-.

.0970.. 0980 (2.464-2.489)
.0965-. 0975 (2.451 -2.477)
.0965.. 0975 (2.451-2.477)
.1880-. 1897 (4.775-4.818)

.0002-. 0007 (.005-.Ol8)

.070-. 120 (1.78-3.05)

.005-.

1

0.005

(0.127)

0.001 (0.025)

-;I

32)

0075 (.140-.191)

.010-. 020 (.25-.51)

Thumb Push Fit

Counterclockwise

030 (.030-.760)

c

4

VALVE-I NTAKE

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Stem Diameter (Stem is tapered)
**Center
**Face

Valve Face..

Guide Clearance

VALVE-EXH AUST

Stem Diameter

Guide Clearance

Valve Face..

VALVE

Length
Outside Diameter
Inside Diameter (after reaming)

Exhaust
Intake

Cylinder Block Bore Diameter..

VALVE SEATS

Bore Diameter

Insert Outside Diameter
Seat Width..
Angle..
Available Insert Oversizes

VALVE SPRINGS

Load-Valve Closed
Load-Valve Open (RDJC Prior to Spec P)
Load-Valve Open (RDJF, RDJC Begin Spec P)

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

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

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

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

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

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

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

GUIDE

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

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

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

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

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

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

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

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

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

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

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

i

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

.4690-.4695 (1 1.9126-11.9253)

1.364-1.365 (34.6456-34.6710)

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

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

.3401--3411 (8.639-8.664)

-3386-.3396 (8.601 -8.626)
42"

.0015--0030 (.038-.076)

.3405-.3415 (8.649-8.674)

.0030-.0050

.3445-.3455 (8.750-8.776)
.3425-.3435 (8.700-8.725)

.467-.468 (11.8618-11.8872)

1.361-1.362 (34.570-34.595)
.047-.062 (1.19-1.57)

45-49 Ib (200-218
83-93 Ib (369-414
87-97 Ib (388-432

(.076--127)

45"

1.7812 (45.2424)

45'

.002 (.0508)

-005

(.127)
.010 (.254)
.025 (.635)

N*)

N*)
N*)

*N. Base unit, Newtons. Unit

**Measure intake valve stem at points indicated.

of

force.

Valve Stem Diameter

(Intake)

--

2.96 in

(75.2

mm)

1.18

in

FACE

CENTER

5

Assembly

Redistribution or publication of this document, 

by any means, is strictly prohibited.

The assembly torques given here will assure proper
tightness without danger of stripping threads. If a
torque wrench is not available, estimate thedegree
tightness necessary for the stud, nut, or screw. Be
careful not to strip threads. Use reasonable force only
and a wrench of normal length.

Specially designed place bolts do not require a
lockwasher or gasket. Do not attempt to use a
lockwasher with these bolts; it will defeat their
purpose. Check all studs, nuts and screws often, and
tighten as needed to keep them from working loose.

Torques

of

and

Special

Tools

S.PECIA.L

These tools are available from Onan to aid service
and repair work.

Diesel Nozzle Tester
Diesel Pintle Nozzle Cleaning

Set (includes injection nozzle
centering tool)

Driver, Center Camshaft Bearing

(RDJ F only)

Driver, Valve Seat

Oil

Seal Guide and Driver..

Wrench, Oil Filter (for Purolator

full flow filter).
Nozzle Centering Sleeve.
Delivery Valve Test Fixture

Combination Main and Cam

Bearing Driver
Diesel Compression Tester

Valve Spring Compressor
Valve Seat Remover

Flywheel Puller

Crankshaft Gear Puller
Crankshaft Gear Pulling Ring
Tool Catalog

TOOLS

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

Tool

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

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

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

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

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

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

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

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

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

Tool

...........

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

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

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

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

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

420-01 84

420-0208

420-0254
420-0270
420-0250

420-0268

420-0321
420-0322

420-0326
420-0283
420-01 19
420-031 1
420-0100
420-0072
420-0248
900-001 9

TO

RQ

U

E SPEC I F I CAT1 0 NS

Center main bolt
Connecting rod bolt
Rocker-Box cover
Cylinder head bolt.

Exhaust manifold nuts
Flywheel mounting screw

Fuel pump mounting screws
Gear case cover
Glow plug..

Injection nozzle mounting

screws

Injection pump mounting

screws
Intake manifold.
Oil base mounting screws..
Oil Filter

Oil

Rear bearing plate.
Rocker arm nut..
Rocker arm stud..

*

-

**

-

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

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

..........

pump mounting screws..

Exhaust nuts must be tightened evenly.

This torque is due

only and
arm nut to adjust valve lash.

(4

cylinder).

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

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

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

..........

.......

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

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

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

Hand tight plus

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

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

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

to

locks

friction between the threads

the nuts in place. Use the rocker

...

....

.....

....

Ft.-Lb.

97-102(131-138)

27-29 (37-39)

8-10 (11-14)

44-46 (60-62)

13-15* (18-20)

65-70 (88-95)

15-20 (20-27)
18-20 (24-27)
10-15 (18-20)

20-21 (27-28)

15-16 (20-22)

13-15 (1 8-20)

45-50

1/4

15-20 (20-27)

40-45 (54-61)

4-lo** (5-13)

35-40 (48-54)

to

Nom

(61-68)

1/2

turn

..

.5

.

I

6

Engine

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Troubleshooting

e

0

0

0
0

0

e

e

Incorrect

Timing

Restricted Air Intake -Dirty Air Filter
Pow Quality Fuel

Dirw Fuel Filters

Our

of

Fuel

or

Worn

Faulty Injection Pump.

Fuel Line Leaks
Wrcq Timing
Wrong Thickness Pump Mounting Gaskets

Run

Loose

Binding Linkage

Exccrrive

Incorrect

High Spring Sensitivity

Incorrectly

lnrufflclent Coolanl

FauIw

Warn

Water Passages Restrimed

Blawn Head Gasket

Ovcrhratinm

-

-

Restricted

Defective

Inadequate Air Circulation

Shut Off Closed

or

Damged

Transfer Pump. Leaking Diaphragm

Button

For

Long Periods of Tlmc

or

Disconnected Linkage

Wear

in Linkage

Governor Adjustment

Installed Governor Yoke

Thermosrat

,

..

~.

~~~ ~

Water Pump

or

.

01

Too Long

Expansion

Nozzles

or

Garters

in Injection Pump

at

NO

Defective

Seals

Water

Liner

Tank Pressure Cap

LOAD

01

Cup

7

Poor Compression
Loose Piston
Loose

Conncctmg

lncorreci

Valve

Broken

01

Weak

High

Exhaust

Not

Bearings

Cylinder

Valves

nr

Dwry

Back

Seating

Walls.

Valve

Valves

worn

Worn

Stickinz

Wwn

Rod

Clearance

Valve

Same
Pressure
Properly

Pistmr.

Guides

or

Crankshaft Bearing

.-

Rings

Service and Maintenance

Redistribution or publication of this document, 

by any means, is strictly prohibited.

PRE-STARTING

Preparations for the initial and each additional star-

ting operation should include careful checks of the

oil, fuel, cooling, and electrical systems.

Before engine is put in operation, check all com-

ponents for mechanical security. If an abnormal
condition, defective part, or operating difficulty is
detected, repair or service as required. The engine

should be kept free of dust, dirt, and spilled oil orfuel.

Be sure proper operating procedure is followed.

Crankcase

Multi-grade oils (such as 5W-30) are recommended
for service in ambient temperatures of 32OF. and
colder. On Onan

15W-40 or 20W-40 oils (CD/SE Service Designation)
may be used in an ambient temperature range of

(-10°C) through 90°F (32°C). Refer to the oil chart
below for recommended viscosity grades at various
temperature ambients.

Oil

J

Diesel liquid cooled engines, SAE

15"

F

Recommended Fuel

Use ASTM 2-D or 1-D fuel with a minimum Cetane
number of 45*. Number 2 diesel fuel gives the best
economy for most operating conditions; however,
use ASTM 1-D fuel during the following conditions:

1.

When ambient temperatures are below 32OF

(0"

C);

2. During long periods of light engine load; or no
load.

"NOTE: Fuels with Cetane numbers higher than
in higher altitudes or when extremely low ambient temperatures
are encountered to prevent misfires.

Use low sulfur content fuel having apourpoint (ability
to filter) of at least 10" below the lowest expected
temperature. Keep the fuel clean and protected from
adverse weather. Leave some room for expansion
when filling the fuel tank.

Due

to

the precise tolerances of die-

sei injection systems, it

important that the fuel be kept clean. Dirt in the

tem can cause severe damage

to

pump and the Injection nozzles.

WORK TRANSFER PUMP

PRIMING LEVER UNTIL

FUEL FLOWS FROM
RETURN LINE FITTING

OF INlECTlON PUMP.

45

may be needed

is

extremely

sys-

both the injection

I I

0

-2b

ERATURE RANGE YOU EXPECT BEFORE NEXT

20

-10

I

.

40

0

1

'

10

60

-20

80

Use oil with an API classification of CD/SE (all viscos­ity grades) or CC/SE (grades 1OW-30, 1OW-40, or

5W-30 only).

When adding oil between oil changes, it

is

to use the same brand, as various brands of oil may

not be compatible together. Refer to the Operator

and Service Maintenance Schedule on page

oil

recommended

WARNING

m

NOT

check oil while the engine is operating.

change intervals and procedures.

Crankcase pressure could blow

hot oil and cause serious burns. Do

I

30

OIL

I

100

40

CHANGE

preferable

11

for

out

FIGURE

If

the camshaft pump lobe is up, crank engine one revolution to
permit hand priming. When finished, return priming lever inward
(disengaged position) to permit normal pump operation.

1.

BLEED FUEL SYSTEM

8

Bleeding

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Fuel

System

Bleed air from fuel system as follows: Disconnect fuel
return line, Figure

1-

Operate

hand

priming lever on

fuel transfer pump until fuel flowing from fuel return

line is free of air bubbles. Then reconnect the fuel
return line.

PRE-HEATING AND STARTING

Preheating for

DJ-Series Diesels at
seconds for temperatures above
to Onan Dieselstarting Guide, for additional starting

guidelines.

-_

-

WARNING

i

death. Be sure deadly exhaust gas is piped outside
and away from windows, doors, or other inlets to

building.

severe personal injury and engine damage.
use ether as a starting aid; heat or compression or
heat from the glow plugs may cause a sudden ignition
of the ether vapor.

1.

Engage PREHEAT switch for the time period
recommended below:

30

seconds if above

60

seconds if below 55°F

2.

Engage START switch while continuing preheat.

Hold until engine comes up to speed.

3.

If engine fails to start in 15-20 seconds, repeat

60

seconds is recommended

55°F

(13°C)

or lower, and

55"

F

(13°C).

on

Refer

inhalation of exhaust gases might
resuit in serious personal injury or

Use of ether as a starting aid might
cause an explosion resulting in

Do

not

55OF

(13°C)

-

(13°C).

all

30

steps

1

&

2-

Absence of blue exhaust smoke dur-

ing

cranking indicates no fuel being delivered.

Determine cause.

4.

In

extreme cold

preheating up to

it

may be necessary to maintain

2

minutes after the engine starts
to obtain firing or to smooth out all cylinders,
especially at no load or light loads.

To

CAUT,ON

prevent heater burnout and

conserve baftery, do not exceed
the one minute preheat periods. Longer preheat­ing time prior to cranking the engine can ruin the
manifold heater and glow plugs because there is
no incoming air flow to cool them. Additional
operation of the preheaters for a few seconds
during cranking in cold weather may help to pre­heat the incoming combustion air and prevent
misfires as the engine starts running.

Verify that oil pressure gauge reads at least

5.

after engine reaches speed (pressure relief valve
is not adjustable).

Do

not apply overvoltage to the

starting circuit at any time.

Overvoltage will destroy the glow plugs and air

heater.

if

it becomes necessary to use an addi­tional source of power to start the set, use a
volt battery connected in parallel.

STOPPING

Push fuel solenoid switch to Stop position.

1.

Release switch when set stops. If stop circuit fails,

2.

close fuel valve.

20

psi

72

BEFORE

I

STARTING:

PRIME FUEL SYSTEM
SYSTEM WAS JUST INSTALLED. FUEL TANK RAN

IF

FUEL FILTERS WERE DRAINED

CHECK FUEL SUPPLY.

BE SURE SHUTOFF VALVES ARE OPEN.

I

DRY.

OR

CHANGED.

--

TO PRIME FUEL SYSTEM:
MOVE PRIMING LEVER UP

AND DOWN UNTIL FUEL
FLOWS STEADILY FROM

RETURN LINE (DISCON­NECTED).

FUEL TRANSFER

PUMP

PRIMING LEVER

FUEL RETURN LINE

To

START:

IF ENGINE FIRES BUT DOES NOTSTART. REPEATABOVEPROCEDURES. INCLUDING

PREHEAT. LIMIT CRANKING

ENGINE STILL DOES NOT START. SEE-IF ENGINE FAILS TO START INFORMATION.

<

PREHEAT COLD ENGINE PUSH PREHEAT SWITCH AND HOLD

TO

?*

-

30

SECONDS IF ABOVE 55-F

60

SECONDS IF BELOW 55.F (13°C).

NEVER PREHEAT MORE THAN

15

TO

20

SECONDS TO CONSERVE BATTERY. IF

FUEL FILTERS

(13

C):

60

SECONDS.

.

-

IF

Redistribution or publication of this document, 

by any means, is strictly prohibited.

ENGINE FAILS

TO

START:

KEEP ENTIRE FUEL SYSTEM CLEAN AND FREE FROM WATER

DIESEL INJECTION

INJECTION PUMPS AND NOZZLES ARE NOT FIELD REPAIRABLE

BLUE-WHITE EXHAUST SMOKE:

ENGINE

IS

GETTING FUEL

I

CHECK PREHEAT SYSTEM:

1.

OBSERVE AIR HEATER
THRU AIR INLET.

2.

ENGAGE PREHEAT.

3.

IF HEATER ELEMENT DOES

NOT GLOW RED WITHIN

30

SECONDS. CHECK AIR

HEATER AND GLOW PLUG

WIRING:

CONNECTIONS TIGHT?
FREE FROM CORROSION?

1

8-79

98-4006

PUMPS

WILL FAIL IF SYSTEM CLEANLINESS

LITTLE

OR

PRIME FUEL SYSTEM. OBSERVE FUEL FLOW FROM RETURN LINE.

NO EXHAUST SMOKE ENGINE

I

FUEL FLOWS STEADILY LITTLE

I

II

I

I

-THROTTLE

IF ENGINE

1.

CRANK ENGINE AND OBSERVE FUEL FLOW FROM RETURN LINE.

2.

IF FUEL DOES NOT SPURT OUT. PUMP MAY BE DEFECTIVE.

I

CHECK FUEL SOLENOID:

ON. IF NOT. CHECK FOR

BINDING LINKAGE

SOLENOID

IS

STILL NOT GElTlNG FUEL, CHECK TRANSFER PUMP

ROD

ARM

IS

NEGLECTED

IS

NOT GETTING FUEL.

I

CLOGGED FUEL FILTERS?

I

OR

.

1

NO FUEL FLOW

I

IF ENGINE STILL DOES NOT START. CONTACT AUTHORIZED ONAN SERVICE REPRESENTATIVE

AUTOMATIC STARTING AND STOPPING

Optional controls may be used for automatic start
and stop, but must provide engine preheating.

The automatic control should have

a

time delay relay

to preheat glow plugs and the manifold heater for at

least

20

seconds before cranking occurs. The time
delay relay prevents immediate engagement of the
starter in case the load is reapplied before the engine
stops.

APPLYING LOAD

If practicable, allow engine to warm up before con­necting a heavy load. Continuous overloading causes
high operating temperatures that can damage the
engine. The exhaust system may form carbon depos­its during operation at light loads; apply full load

occasionally before shut-down to prevent excessive
carbon accumulations.

Try to apply the load in steps instead of full load at

one time.

BREAK-IN PROCEDURE

The unit should be run in the following sequence:

1.

One half hour at

2.

One half hour at

3.

Full load.

l/2

3/4

load.
load.

Continuous running under one half load during the
first few hundred hours may result in poor piston ring
seating, causing higher than normal oil consumption
and blowby.

Drain and replace the crankcase oil after first

tion; drain while the engine

is

still hot.

50

hours of opera-

INSPECTION

Check for alignment of engine and load. Misalign­ment will cause excessivevibration and bearing wear.
Make a visual inspection of the entire installation.

Contact with rotating machinery

might cause serious personal injury
or death. Stay clear of rotating components and
ensure that protective shields andguards are in place

and secured before operating machinery.

10

VENT1 LATlO

Redistribution or publication of this document, 

by any means, is strictly prohibited.

N

Good ventilation is needed to cool the engine and to

support combustion. Avoid recirculation of ventilat-

ing

air.

Inhalation

of

exhaust gases might

result in serious personal injury or

death.

Do

not use exhaust heat to warm a room,,

compartment or storage area.

EXHAUST

Pipe exhaust gas outside any enclosure: exhaust gas
is poisonous. Exhaust pipes must not terminate near
inlet vents. Avoid sharp bends. Use sweeping, large-

radius elbows. Use a section of seamless, flexible
tubing between the engine and any rigid pipe to res­trict vibration.

LOW TEMPERATURES

1.

Use correct

tions. Change oil only when engine is warm. If an

unexpected temperature drop causes an emer­gency, move engine to a warm location or apply
heated air (never use open flame) externally
oil flows freely.

2. Use fresh fuel. Protect against moisture conden­sation.

3.

Keep fuel system clean, and batteries
charged condition.

4.

Use additional preheat cycles during cold starts.

out the heater elements.

OPERATOR AND SERVICE MAINTENANCE SCHEDULE

SAE

No.

oil for temperature condi-

until

in

a well

Do

not exceed one minute preheat

periods; longer periods can burn

BATTERIES

Check the condition of the starting batteries at least
every two weeks. See that connections are clean and
tight. A light coating of non-conductive grease will

retard corrosion at terminals. Keep the electrolyte at
the proper level above the plates by adding distilled
water. Check specific gravity; recharge if below

1.260.

DUST AND DIRT

1. Keep inlet screen free

2. Service air cleaner as frequently as necessary.

3. Change crankcase oil every

4.

Keep oil and fuel in dust-tight containers.

5.

Keep governor linkage clean.

of

dirt, etc.

50

operating hours.

HOURS

OPERATION

conditions)

OF

100

200

500

600

2000

3000

5000

MAINTENANCE TASK

1.

.

I

Clean governor linkage
Change crankcase oiT
Drain fuel condensation traps
in lines and filters,

I

seeNote1

I

Replace oil filter

rn

Check battery condition
Clean breather standpipes

rn

Check start-disconnect circuit
Check valve clearances

Change primary fuel filter
Grind valves

rn

Clean holes in rocker box
oil line orifices
Check nozzle spray pattern,
see Note

Change secondary fuel filter
General overhaul (if required)

see

Note

2

3

(if

required)

.

HIGH ALTITUDE

Maximum power will be reduced approximately
percent for each 1000 feet (310 m) above sea level,

after the first 1000 feet (310 m).

4

11

NOTE

1.

Water or foreign material in fuel can ruin the injection
system.

dirt in sediment bowl fuel, handling and storing facili-

ties should be checked and situation corrected. Prim-

ary and secondary fuel filters must be replaced follow­ing correction of fuel contamination problem.

2.

This service must be conducted by trained diesel injec­tion equipment personnel with suitable test facilities.
Omit this service until these conditions can be met.

3.

Tighten head bolts and adjust valve clearance after first

50

If

daily inspection shows water or excessive

hours on an overhauled engine.

OIL

Redistribution or publication of this document, 

by any means, is strictly prohibited.

FILTER

CHANGE

Place pan under old filter and remove by turning
counterclockwise. Clean filter mounting area. Lubri­cate gasket on new filter with oil and screw filter on
clockwise until gasket touches mounting base, then
tighten 1/2 turn.

OIL

DRAIN

For service convenience, install a short (less than

EXTENSION

10

inches [254 mm]) oil drain extension made from

standard pipe and fittings,

pipe-tapped oil drain hole

in

the1/2-inch (12.70 mm)

in

the base.

Crankcase pressure couid.biow

hot oil and cause serious

NOT

check oil while the engine is operating.

CAP AND OIL LEVEL

OPERATE ENGINE

ITH OIL BELOW

THIS LEVEL

HIS

LEVEL

burns.

out

Do

CRANKCASE

BREATHER

PIPE

INSERT A
WIRE
BREATHER PIPE
TO CLEAN

W

.BREATHER SYSTEM

SOFT

THROUGH

OILLEVEL

FUEL PUMP

i.

FUEL TRANSFER PUMP

INDICA'TOR'

,.-\

BALL

I

NL.ET OUTL.ET

FILTER FILTER

JOINT

ONDARY

DUAL FUEL FILTER SYSTEM

FIGURE

2.

MAINTENANCE PROCEDURES

12

OUT-OF-SERVICE PROTECTION

Redistribution or publication of this document, 

by any means, is strictly prohibited.

The natural lubricating qualities of
should protect a diesel engine for at least 30-days
when unit is not in service. To protect an engine that
will be out of service for more than 30 days, proceed
as follows:

1.

Run engine until thoroughly warm; under at least.

50

percent load.

2.

Shut down engine and drain oil base while still
warm. Refill and attach a warning tag indicating
viscosity of oil used.

3.

Remove glow plugs. Pour l-ounce of rust inhibi­tor (or SAE #10
glow plugs.

hand. Starter cranking is too fast; oil or inhibitor
fiuid will fire
room temperature.

4.

Service air cleaner per

5.

Clean throttle and governor linkage and protect
by wrapping with a clean cloth.

Plug exhaust outlets to prevent entrance of mois-

6.

ture, bugs, dirt, etc.
Clean and wipe entire unit. Coat parts susceptible

7.

to rust with a light coat of grease or oil.

Disconnect battery and follow standard battery

8.

storage procedure.

oil)

into each cylinder. Install

To

distribute oil in cylinder,

crank (or turn over) engine by

if

cranked with starter at normal

Maintenance Schedule.

No.

2

diesel fuel

Returning a Unit

1.

Remove cover and all protective wrapping.
move plug from exhaust outlet.

2.

Check warning tag on oil base and verify that
viscosity is still correct for existing ambient tem-

Deratu re.

3. Clean and check battery. Measure specific grav­ity (1

-260

ring. If specific gravity is low, charge until correct

value is obtained. If level is low, add distilled
water and charge until specific gravity is correct.

DO

NOT

sonal injury. Do not smoke while servicing batter­ies.

4.

Check that fuel injectors and fuel lines are secure

and correctly torqued.

5.

Clean heat exchanger.

6.

Connect batteries.

7.

Verify that no loads are connected to engine.

71

injury or death. Be sure deadiy exhaust gas is
piped outside and away from windows, doors, or
other inlets to building.

8.

Start engine.

After engine has started, excessive amount
be exhausted until the rust inhibitor or oil has burned away.

to

Service

at

77"

F

[25OC]) and verify level is at split

OVERCHARGE.

lgnition of explosive battery

gases might cause severe per-

lnhalation of exhaust gases
might result in serious personal

of

blue smoke will

Re-

oil

Accidental starting of the engine

might cause severe personal injury
or death. Disconnect the battery cable when repairs
are made to the engine, controls, or generator.

13

Exhaust

Redistribution or publication of this document, 

by any means, is strictly prohibited.

System

GENERAL

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.

Back pressure must not exceed 27 inches
of water column for the rated load when measured
with a manometer at the exhaust manifold, Figure

INCHES

OF

WATER
INCHES

OF

MERCURY
OUNCES

(686

mm)

3.

Inhalation

result in serious personal injury
death. Inspect exhaust system audibly and visually
for leaks daily. Repair any leaks immediately.

INSTALLATION

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 the engine as

possible. Mufflers which are too far from the
manifold remain cool and collect carbon residue.

Pitch exhaust pipe upward from exhaust outlets

to avoid entrapment of raw diesel fumes in muffler
at shutdown.

Avoid sharp bends by using large radius elbow.
Check back pressure with a mercury or water

column type manometer.
Position the exhaust outlet away from the engine

air intake.

TIPS

of

exhaust gases might

or

.Ill

.....

FIGURE

Exhaust

A

light gray or light blue smoke may be a 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.

Black smoke indicates overfueling (more fuel than
oxygen) and is usually caused by overloading. The
smoke or unburned fuel becomes carbon when
raised to a high temperature. Carbon contributes to
engine damage because

ing oil.

WARNING

LiIl

death.

compartment, or storage area.

Vent exhaust gases outside. Use flexible tubing only

between the engine exhaust outlet and rigid piping.

3.

BACK PRESSURE TEST WITH MANOMETER

Smoke

it

contaminates the lubricat-

Inhalation
result In serlous personal Injury or

Do

not use exhaust heat to warm a room,

of

exhaust gases might

Exhaust noise can be suppressed or reduced by:

Using a heavy duty exhaust system with a more
efficient muffler.

,

Avoiding use of flexible lines.
Installing a deflector at the exhaust outlet to

direct exhaust toward the ground, but away from

the operator.

Using a resonator in addition to a muffler.

The importance of exhaust systems (normally
supplied by the customer) cannot be over­emphasized.

power, overheating and engine damage. A poor

exhaust system increases back pressure which

reduces efficiency.

tions engineer must approve the installation for war-

ranty purposes.

A

poor or clogged system causes low

If the manufacturer tailors his own
exhaust system, an Onan applica-

INDOOR INSTALLATIONS

Locate exhaust outlet far from air inlet to avoid
recirculation. The engine exhaust is tapped for 1-1/2
inch thread. Use flexible tubing to connect theengine
exhaust to rigid pipe or muffler. Shield the line if
passes through a combustible wall (Figure
are necessary, use sweeping (large radius) elbows. If
pitched upward, install acondensation trap at point of
rise, Figure

5.

4).

it

lfturns

14

As

Redistribution or publication of this document, 

by any means, is strictly prohibited.

the exhaust pipe length and number

of

bends

increases, larger pipe is required to eliminate exces-

sive exhaust restriction and back pressure.
The chart below shows the maximum equivalent

exhaust pipe length for exhaust systems using
through 3 inch pipe.

lengths of various pipe fittings. The

Also

shown are the equivalent

TOTAL

1-1/2

exhaust

system equivalent length (including all fittings and

muffler) should not exceed the length shown in the
chart for the size of pipe used. Use a manometer to
verify that back pressure does not exceed

(686

rnm) H20.

27

inches

MAXIMUM EQUIVALENT EXHAUST PIPE

LENGTH-ONE CRITICAL MUFFLER INCLUDED

PIPESIZE (INCHES)

LENGTH IN FEET

AND METRES

(1.5-Inch

LENGTH IN FEET

AND METRES

(2-Inch

Muffler)

Muffler)

1.5 1.75 2.0 2.5

4 9 18 49 160

(1.2) (2.7)

17 35 70 188 614

(5.2)

(5.5) (15) (49)

(11)

(21) (57) (187)

3

SINGLE THIMBLE DIAMETER

I~"~OS

DOUBLE VENTILATED THIMBLE
DIAMETER

THAN EXHAUST LINE

mm)

LARGER

6"(

s

IN END

SLEEVE

I52

mm)

OR

LARGER

EXHAUST LINE PASSING THROUGH

II

WALL OR PARTITION

FIGURE

4.

EXHAUST SHIELD

EQUIVALENT LENGTHS OF PIPE FITTINGS

TYPE OF FITTING

(INCHES)

STANDARD ELBOW

Feet (Metres)

LONG RAD. ELBOW

Feet (Metres)

MED. RAD. ELBOW

Feet (Metres)

STANDARD TEE

Feet (Metres)

1.5

I

2

(1.34) (1.62)

(0.85) (1.07)

(1.10) (1.40)

9.3

(2.83) (3.96)

2.5

6.4

(1.95)

4.2

(1.28)

5.4

(1.64)

14

(4.27)

(2.47)

(1.58)

(2.07)

(5.18)

EXHAUST GAS

Exhaust gases contain carbon monoxide, a poisonous gas that might cause
unconsciousness and death. It is an odorless and colorless gas formed during
combustion of hydrocarbon fuels. Symptoms of carbon monoxide poisoning
are:

Dizziness Vomiting
Headache Muscular Twitching
Weakness and Sleepiness

\

IF

UPWARD CONSTRUCT A TRAP

3

8.1

5.2

6.8

17

FITTINGS AT POINT OF RISE

AG17

FIGURE 5. CONDENSATION TRAP

WARNING^

IS

DEADLY!

Throbbing in Temples

EXHAUST LINE MUST BE PITCHED

DRAIN CONDENSATION TRAP

PE RlODlCALLY

OF

PIPE

If you experience any of these symptoms, get out into fresh air immediately,
shut down the unit and

The best protection against carbon monoxide inhalation is proper installation
and regular, frequent inspections of the complete exhaust system.
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.

do

not use until it has been inspected.

15

If

you notice

Cooling

Redistribution or publication of this document, 

by any means, is strictly prohibited.

System

PURPOSE

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 sys-

tem must carry off the excess heat.

Regulating coolant temperature helps keep the engine
at the optimal heat level for each operating condition.
After starting, the engine must warm up quickly. Dur-

ing periods of peak output, it must be adequately
cooled.

OF

COOLING SYSTEM

ANTI-FREEZE AND CORROSION

Corrosion can shorten an engine's life by plugging up
radiator cores, building up around hot spots near the
exhaust valves, and settling in low areas of the block.
The corrosive sediment insulates against proper heat

transfer and holds heat in. Most of the metals used in

cooling systems are susceptible to corrosion damage

that causes coolant leaks and the temperature to rise

above safe, normal limits.

To prevent corrosion, a mixture of anti-freeze and
water should always be used as an engine coolant,
even when freezing temperatures are not expected.

Besides preventing coolant freeze up, anti-freeze

contains rust inhibitors that prevent corrosion. Most
an ti-f reeze manufacturers recommend a mini mum

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 avoid corrosion and

more expensive damage.

COOLING SYSTEM MAINTENANCE

The cooling system including the block and radiator
should be cleaned and flushed at least once a year.
This

is

especially true in cold weather conditions or

when preparing unit for extended storage (over

days or more)!

The cooling system can work efficiently only when it

is clean. Scale and rust in the cooling system slow
down heat absorption and restrict water flow.

The thermostat is calibrated to open at 150°F

should be checked also.
An appropriate anti-freeze mixture should be used in

colder climates as necessary.

Check the fan belt tension periodically. For proper
operation of the water pump, the fan belt should be
tight enough to prevent slipping.

Check the water pump for wear periodically. Loosen
the fan belt and move the fan and water pump pulley

back and forth. If wear is excessive, replace the
bearing.

Cleaning and Flushing Cooling System

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

Contact with hot coolant might

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

30

*

2OF.

It

I

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 the circuit 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.

Cleaning solutions typically contain

strong chemicals that can cause
burns or other injury if used improperly. Read all
warning labels carefully before using.

When cleaning is complete, drain cleaning solution

and flush system. For best results engine 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 wafer into a hot

so

engine. Doing
head or the cylinder block. Do not operate engine
without coolant for even a few minutes.

Flush system if engine operation indicates clogged
passages or overheating.

may crack the

16

Engine Water Jacket and Cylinder Head

Redistribution or publication of this document, 

by any means, is strictly prohibited.

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 accumulations 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.

Draining Cooling System

Whenever draining the cooling system for changing

anti-freeze solution or for out-of-service protection

when only water is used, be sure to open all drains

and hose connections where water could be trapped.

Contact with hot coolant might

result in serious burns.

hot, pressurized coolant from

system.

The following drain plugs must be removed to allow

complete flushing of the cooling system.

Radiator:
Engine

One petcock lower right front corner.

Block

One drain plug left front near water

Pump.

Water

Pumps:

One drain plug under cover or by

ening cover.

If

an optional water jacket tank heater

and flushed also. The lower hose must be disconnected at the tank

heater. There is no drain plug.

is

used it should be drained

Do

not bleed

a

closed cooling

loos-

Thermostat

Replace thermostat if
in the open or closed position. If engine overheats or
does not reach and maintain a minimum operating
temperature, the thermostat should be removed and
tested as a possible cause.

1. Remove thermostat from cylinder head.

2. Heat a pan of water to approximately 150°F.
Check temperature using a thermometer im­mersed in water.

3. With thermostat suspended in water at tempera-

ture of 150°F, thermostat should start to open.

4.

After thermostat has opened completely, remove

it

from hot water and allow it to cool in surround-

ing air. The thermostat should close within a

short time.

5.

If the thermostat sticks or does not operate prop-

erly, replace

6.

Always install a new gasket when replacing the
thermostat.

it

is broken, corroded, or sticks

it

with'a new one.

After making repairs on the cooling system, tighten
all connections thoroughly. Use Permatex or thread
sealing compound on all threaded connections to
prevent leaks or the entry of air into the system.

Read instructions on Permatex Sealer can before applying sealer
to engine parts.

Pressure Cap

The pressure cap increases the boiling point of the
coolant by allowing pressure to build up in the cool-

ing system. The increase in boiling point reduces the

chances for coolant loss due to boil over. A 15 psi

(103.5 kPa) pressurecap will raise the boiling point of

water to 250°F (122°C) and the boiling point of a

50/50

(132°C). Pressure caps should be inspected periodi­cally for freedom of operation and the gasket should
be checked for proper sealing. Replace the pressure
cap if it malfunctions.

mixture of water and anti-freeze to 265°F

17

RADIATOR COOLED

Redistribution or publication of this document, 

by any means, is strictly prohibited.

SYSTEM

On radiator cooled models (Figure 6), the water

pump draws cooled water from the radiator through

the bottom hose and forces it into the cylinder water
jacket at the front of the engine. The water circulates
through the cylinder water jacket up through the

cylinder heads to the thermostat and flows through
the outlet hose into the top of the radiator.

It

circu­lates down through the radiator while the fan blows
cooling air across the radiator. The water is drawn

from the bottom of the radiator by the pump to be

recirculated.

Water Pump

A

centrifugal type water pump (Figure 6a) circulates
coolant through cooling system. The water pump is
secured to cylinder block with 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.
assures a leakproof connection.

A

gasket on water pump outlet

WATER

PUM,P

LEGEND

-

-

WATER FLOW, ENGINE COOLING

-AIR FLOW. ENGINE VENTllATlON

FIGURE

6.

RADIATOR

COOLING SYSTEM

During engine, warmup, when the thermostat is

closed, the water bypasses the radiator.

It

flows
through a bypass line from the water outlet housing
to the pump and recirculates through the engine.

When water in the e.ngine block reaches normal

operating temperature, the thermostat opens. This
permits heated water to flow into the radiator to be
cooled.

Recirculation ensures both rapid and even tempera-

ture increase of all engine parts during warmup.
Ventilation for radiator cooled models requires an

inlet opening for fresh air and an outlet opening for
hated air to prevent recirculation

of

heated air. The

openings should be at least the size of the radiator.

An expansion area in fhe closed

cooling system maintains proper

coolant level

by

prevenfing overflow and loss of cool-

ant when engine heats up.

FIGURE

PUMP

6a.

WATER PUMP-EXPLODED VIEW

BY-PASS

I

LINE

HOUSING

GASKET

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 is especially harmful to pump
parts.

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.

Removal and Installation

1.

Drain cooling system at radiator and engine
block.

Remove housing from radiator as necessary.

2.

Disconnect both hoses from radiator.

3.
Remove radiator.

4.

Loosen fan belt.

5.

Remove fan and water pump pulley.

6.
Disconnect by-pass line and radiator lower hose

7.
from pump.

Remove water pump from water pump housing.

8.

Installation is the reverse

9.

of

removal.

18

CITY WATER COOLED

Redistribution or publication of this document, 

by any means, is strictly prohibited.

On citywater cooled models (Figure7) the lockshield
valve is manually adjusted with a key forthe required
minimum rate of water flow for cooling. Wheneverthe
ignition is turned on, the solenoid valve opens the
pressurized water inlet line.

During operation, water from the pressurized source
flows through the lockshield valve and solenoid valve

and the inlet line and enters at the bottom of the

cylinderwater jacket at two places, one entry for each
pair of cylinders. The water circulates around

the cylinder jacket through the cylinder heads where

it

leaves the engine through a thermostat and cover at

each

of

the two cylinder heads. From the thermostat

covers, the water passes through the exhaust mani-

fold and is drained from the engine cooling system.

During engine warmup, when the thermostats are
closed, a water by-pass line controls the amount of
water through the cylinder water jacket until the
thermostats open. The by-pass line also continues to
function during operation because

it

high water temperature cut-off switch and the water
temperature sender unit.

Ventilation for these models is necessary for suffi­cient fresh air movement

to

cool the generator and

support combustion for the engine.

and

up

contains the

Check the thermostat opening and closing with the

thermostat immersed in a water bath. The thermostat

should start to open when the water temperature

reaches

Take the thermostat out of the water and

close in approximately 60 seconds. If
operate properly, replace

HEAT EXCHANGER COOLING

145°F

and should be fully open at 165°F.

it

should

it

does not

it.

(Optional)

ONAN heat exchanger cooling is available eitherfac­tory installed or as a kit for customer installation. A

complete heat exchanger installation (Figure 7a)
contains two independent water systems:

1.

A closed water system

2.

An open (raw) water system

In

the closed water system, a centrifugal pump draws
the water from an expansion tank and pumps it
through cooling tubes in a heat exchanger and into
the engine water jacket where

it

circulates out through
a thermostat back into the expansion tank for recircu­lation. In the open water system, pressurized water is

forced around the cooling tubes through the heat
exchanger and through the exhaust manifold from
where it is discharged.

+

-

--*--*

./\N-

HIGH

WATER

TEMPERATURE

CUT-OFF SWITCH WATER BY-PASS

LENOID VALVE

LEG END

WATER INLET
CIRCULATION
WATER

OUTLET

WATER TEMPERATURE

SENDERUNIT

AW WATER INLET LINE

\',

FIGURE

7.

CITY

WATER COOLING SYSTEM

19

ABOZi

Redistribution or publication of this document, 

by any means, is strictly prohibited.

RAW COOLING WATER

FROM SOURCE

CENTRIFUGAL

PUMP

++

--f

RAW WATER

--

WATER

IN

CLOSED SYSTEM

FIGURE

7a.

HEAT EXCHANGER COOLING SYSTEM

Maintenance of the closed water system is the same
as a radiator cooled system. Clean and flush it once a

year and use an anti-freeze if there is danger of freez-

ing. Usea rust inhibitor

in

theexpansion tank (closed

water system).

In the open water system, check periodically for air
leaks, wear or damage, or restricted lines.

The open water portion of the heat exchanger is pro­tected from corrosion by a zinc pencil mounted on a
pipe plug

in

one end of the heat exchanger. Inspect
the pencil at least every two months and replace if
deteriorated to less than one half original size
(Figure 7b.).

FRESH

ZINC

PENCIL

RAW

WATER

IN IN

WATER

Clean and flush the cooling system if conditions war-

.

rant. To clean the closed water system, drain and
refill with radiator cleaner. When chemical cleaning is

completed, according to the cleaner manufacturer’s

instructions, flush the cooling system to wash out

deposits loosened by the chemical cleaning.

Flush the engine water jacket. The hose from engine
water jacket to heat exchanger should be removed
from the water outlet. Flush both closed water portion
and raw water poriton of the heat exchanger. Remove

the lockshield valve and solenoid valve to flush the

raw water portion.

Also

flush the water cooled
exhaust manifold. When flushing is completed, check
the system thoroughly for any leaks uncovered by the
cleaning operations.

I

A801

FIGURE

7b.

HEAT EXCHANGER AND ZINC PENCIL

Repair .and test raw water system for air leaks and
insufficient water flow.

it

Heat exchanger repair, if

should become clogged,
consists of removing the ends and cleaning out the
tubes:

20

Water

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Pump repair is necessary if pump

Pump

is

leaking or bear­ings are worn. Disassemble pump and replace worn
components (Figure 7c.).

1.

Remove the water inlet fitting, drive belt pulley,
cover screws, and pump cover gasket.

2.

Unscrew the threaded impeller from the pump
shaft by turning the impeller in a counterclock­wise direction when facing impeller.

3.

Slide the seal seat, wear face, and bellows
assembly off the shaft. Loosen the clamp screw
and slide the pump body off the pedestal.

4.

Remove the bearing lock ring, and drive the shaft

and bearing assembly out of the pedestal. The

bearing is press fit on the shaft and comes off

one integral part. The bearing

is

packed with a

in

lifelong lubricant and is sealed at each end.

FIGURE

..

..

7d.

WATER PUMP CLEARANCES

.

i

Replace all worn components such as bearings,
seals, wear face, and impeller and use a new cover
gasket. Assembly sequence is the reverse of the dis­assembly procedure.

After the pump has been assembled (see Figure 7d.),

the impeller

(B)

must be centered

in

the body cover
space (C-C). Adjustment is made by moving the
pump body fore and aft until the shaft can be rotated

freely by hand without binding. The pump must be

LOCKING

PEDESTAL

adjusted with the drive belt off. If not centered prop­erly, the impeller will rub on the body or cover and
quickly overheat. Clearance (A-A) may vary from
zero to

1/16

inch

(1.6

mm). Tighten the lock screw
when the adjustment is correct being careful not to
alter the setting.

When the pump is reinstalled on theengine, check to

see that the pump pulley is aligned with the crank­shaft pulley and adjust as required.

FIGURE

7c.

WATER PUMP ASSEMBLY

21

Fuel

Redistribution or publication of this document, 

by any means, is strictly prohibited.

System

DIESEL FUEL

Diesel fuel, like gasoline and most gaseous fuels, is a
product of crude oil refining. Its heat content is

somewhat higher than that of gasoline.

In a diesel engine, fuel is sprayed into the combustion

chamber as the piston approaches the top of its com-

pression stroke. The fuel is ignited by the intense heat
that develops as the air within the engine cylinder is
compressed.

necessary.

Diesel fuel requirements vary with engine size, speed
and load, and with ambient temperature. Factors
which must be considered include the fuel's cetane
number, pour point, viscosity, volatility, and the
amount of sediment, residues, and sulfur in the fuel.

The American Society for Testing Materials (ASTM)

has used these and other characteristics to define
three basic diesel fuel grades. Refer to the Service
and Maintenance section for the recommended grade
of fuel to use in the engine.

Cetane Rating

Cetane number is a measure of how quickly diesel
fuel will ignite under heat and pressure. For proper
engine operation, diesel fuel should ignite almost

immediately after entering the engine combustion
chamber. If ignition is delayed, too much fuel will

ignite at once, causing sudden explosions. These
explosions produce the familiar cackle heard when a
diesel engine is'cold or at idle. If the cackle does not
disappear as the engine is warmed or placed under
load,

it

is a sign that the cetane rating of the fuel may
be too low, which could cause serious engine
damage.

No

electrical ignition system is

Pour

The temperature at which a diesel fuel will cease to
flow is known as its pour point. As diesel fuels
approach their pour point, waxes form and plug fuel

filters causing fuel starvation. For this reason, if low

ambient temperatures are possible, diesel fuel with a
pour point at least
lowest expected temperature should be specified.

Poi

n

t

10

degrees F (6°C) below the

Keeping Diesel Fuel Clean

and

Free From Water

It is essential that diesel fuel be kept clean and free

from water. Diesel injection pumps and nozzles are

precision-made units requiring extremely close tol-

erances. They are very sensitive to any abrasive

materials and are easily damaged by corrosion result-

ing from the introduction of water into the system.

To keep fuel contamination
storage and system maintenance procedures out­lined below must be followed.

1.

Do not use zinc or galvanized storage tanks as
harmful compounds may form as a result of reac­tions with diesel fuel impurities.

2.

Pitch fuel tanks away from the fuel outlet and
provide a drain cock to drain off water and sedi­ment. The fuel outlet should be located several

inches above the bottom of the tank, Figure

3.

Keep fuel tanks as near full as possible to minim­ize condensation within the tank.

4.

Drain sediment traps and change fuel filters on a
regular basis as recommended by the engine
manufacturer.

to

a minimum, the fuel

8.

KEEP

FUEL

CLEAN!

0

DIRTY FUEL

REMEMBER- EVEN A TINY PARTICAL

THE INJECTION SYSTEM MAY STOP YOUR ENGINE!

IS

ONE OF THE MAJOR CAUSES OF

ENGINE FAILURE

0

0

OF

DIRT

IN

22

FIGURE

8.

FUEL

STORAGE

FUEL SYSTEM

Redistribution or publication of this document, 

by any means, is strictly prohibited.

The fuel system (Figure

ment bowl, fuel transfer pump, primary filter, secon-

daryfilter, injection pump, injectors, and the connect-

ing fuel lines.

The fuel system, located on the service side of the
engine, uses a transfer pump to deliver fuel from the
tank to a

14

the injectors at high pressure and act as fuel distribu­tors to the injectors. The time interval between indi­vidual injectors is varied
speed. From the injection pump, metered fuel is
forced through a delivery valve to the injector lines at
about

heated on the compression stroke, the injector

sprays fuel into the hot compressed air where it

ignites. The delivery valve
pintle valve in the injector assists the precision timed
injection of fuel into the cylinder.

Nozzle leak-off fuel is returned to the tank after each
injection cycle by a fuel return line from the nozzle.
An adapter combines the leak-off fuel with the flow­through fuel from the injection pump. A return line
connected at this point returns the combined fuel
back to the fuel supply tank.

of the major causes of diesel engine failure.

piece of dirt in the injection system may stop your

unit. When opening any part of the fuel system
beyond the secondary fuel filter, place all parts in a

pan of clean diesel fuel as they are removed. Before

installing new or used parts, flush them thoroughly,

and install while still wet.

psi

1900

high

(83-97

psi

pressure injection pump at about

kPa). The injection lines deliver fuel to

(13,110

A

or water in the fuel system. It is one

9)

consists of a glass sedi-

12

to

in

the pump by engine

kPa). When the cylinder air is

in

the injection pump and a

diesel engine cannot tolerate dirt

A

tiny

When replacing filter, tighten screw until gaskets

touch base, then tighten screw

1

to

1-1/2

turns.

FUEL TANK AND LINES

Where a separate fuel tank is used, install
vertical distance from bottom of the tank to the fuel
pump does not exceed six feet. Auxiliary fuel pumps
are available to provide an additional eight-foot lift.

Avoid gravity feed of fuel to the engine. Provide a
siphon break if tank is above pump. When sharing a
fuel tank, do not connect to an existing line at a point
above the fuel supply level.

These diesel engines require a fuel supply line and a
separate return line. Install the fuel supply line from
tank to the
nect fuel return line to fitting at injection pump. See

Figure
engine to absorb vibration. Be sure there are no air
leaks

Install a shut-off valve

venience.

WARNING

m

.

sonal injury or death.
Ilnes, fittings, and fuel tanks In the fuel system. Elec­trolytic corrosion mlght cause hazardous fuel leaks.

7/16-24

IO.

Use approved flexible fuel lines at the

in

the suction line.

NPTF inlet in the fuel pump. Con-

in

the tank for service con-

Fuel leakage mlght cause an explo-

sion

or

fire resulting In severe per-

Do

not use dissimilar metal

so

the

FILTER SYSTEM

The sediment bowl has a fine mesh screen which

keeps water and some of the coarse dirt from entering

the transfer pump, Figure

remain in the sediment bowl which should be re-

moved for cleaning as required. The primary and
secondary fuel filters are replaceable units that clean
the fuel of extremely fine particles before it goes to
the injection pump.

These filters are mounted on a common casting
which bolts to the oil fill tube. Positive filtration is
assured because the engine will not run when either
filter is loose or missing.

Average pore size of the secondary filter is

(0.0127

means most particles escaping the primary filter are
trapped

Water in Fuel Filters:

required from both filters. Replace primary filter every

600

mm) smaller than the primary filter. This

in

the secondary filter.

hours and secondary filter every

9.

The dirt and water

0.0005

Drain water periodically as

3000

hours.

FUEL

FILTER

WU

8435

FIGURE

9.

FUEL

SYSTEM

FUEL TRANSFER PUMP

The fuel transfer pump (Figure
and check valve type pump operated by a cam lobe
on the engine camshaft. The pump cam follower has
a wide surface to prevent wear as

10)

is a diaphragm

it

rides on the

23

camshaft lobe. The priming lever is manually oper-

Redistribution or publication of this document, 

by any means, is strictly prohibited.

ated to prime and bleed the system.

The diaphrgam spring maintains required fuel

pressure to the injection pump. Fuel pressure should
be 12-14 psi (83-97 kPa) when operating at 1800 rpm.

Fuel pump pressure may be checked'by connecting a

pressure gauge and tee at the fuel outlet. A vacuum
gauge connected at the fuel inlet will show whether
the pump has enough capacity to lift fuel about

(1.83 m). The fuel pump should produce

15

6

feet

to 18

inches (381 to 457 mm) of vacuum at sea level.

ROCKER ARM

SPRING

.,

DlAPHRAGl

SPRINT.

COVER

PRIMING LiFlK

Assembly:

1.

When installing a new diaphragm, soak it in fuel
before assembling. Insert diaphragm spring and
soaked diaphragm into pump body.

Insert link and rocker arm into body and hook it

2.

'over diaphragm pull rod. Align rocker arm with

rocker arm pin hole and drive

in

lever must be

position shown in Figure

in

pin. The priming

10

when

installing rocker arm.

Compress rocker spring and install between the

3.

body and rocker arm.

4.

Assemble cover to body with notch marks lined
up. Install screws, but do not tighten.

Push rocker arm

5.

in

full stroke and hold in this

position to flex diaphragm.
Tighten cover screws alternately and securely,

6.

then release rocker arm.

Install pump on the engine and repeat pressure

7.

test.

INJECTION NOZZLES

Onan diesel engines use hydraulically-operated,

11.

pintle-type injection nozzles, Figure

tory adjusted to open at 1900 to 1950 psi

13,455 kPa). However, after several hundred hours of

operation the nozzle pressure will decrease to about

1750

psi

(1

2,075

k Pa).

They arefac-

(13,110

to

FIGURE

10.

FUEL TRANSFER PUMP

Fuel Pump Removal Disassembly

1.

Remove pump inlet and outlet lines. Remove two

'

cap screws holding pump to engine and lift it off.

2: Notch the pump cover and body with afileso they

can be reassembled in same-relative positions
and remove six screws holding them together.

3.

Tap body with a screwdriver to separate two

parts. Do not pry them apart; this would damage

h

rag m.

d ia p

Drive out rocker arm hinge pin.

4.

5.

Remove rocker arm, spring and link.
Lift out diaphragm assembly and diaphragm

6.

spring.

Repair:'A kit is available for replacement of the dia­phragm and spring. If the diaphragm is leaking or
broken, check for diluted crankcase oil and replace if
necessary. Occasionally, a worn rocker arm pin will
cause crankcase oil leakage.

If

this is the case, the

pump should be replaced.

COVER

SPINDLE ASSEM

NOZZLE GASKET

OZZLE

NOZZLE CA

FUEL CUP GASKET

CYLINDER HEAD

FIGURE

,-

A880-1

11.

INJECTOR NOZZLE ASSEMBLY
INSTALLATION

SHIELDS

OZZLE ASSEMBLY SHIELD CASK

Operating Principle

Nozzle operation is as follows:

1.

High pressure fuel from the injection pump enters

the fuel inlet stud and flows down drilled

passages

in

the body

of

nozzle holder, Figure 12.

24

2

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Fuel enters fuel duct and pressure chamber of
nozzle assembly. When fuel pressure overcomes

preset pressure of the adjusting spring, the pintle

is

forced upward off itsseat and a fine mist of fuel

is injected
where

into

it

atomizes and mixes with the hot com-

the pre-combustion chamber

pressed air.

3.

If compression temperatures are high enough,
the fuel-air mixture ignites. Injection continues
until the spill port clears the top of the metering
sleeve

in

the injection pump and dumps the high
pressure fuel into the sump allowing the pressure
spring to close the injector and cut off fuel
injection to the cylinder.

Do

not disturb the injector pressure

adjusting screw; it cannot be reset

without proper equipment.

7

GOOD

SPRA~TERN

.bO7

FIGURE

If streamers are visible, the pattern is badly distorted
or the nozzle drips before
pressure, it is defective and must be cleaned or
replaced.

j5:l:

::$!>

:.

,

;,!

i':..

..!

.

.I

.

;I..

,.

w.+

.._

%-

13.

NOZZLE SPRAY PATTERN

it

POOR

SPRAY

PATTERN

reaches opening

Bypass fuel is returned to the tank after each injection

A

cycle by a return line from the nozzle.

fuel return
fitting combines the return fuel from the injectors
with the flow-through fuel from the injection pump
bleed valve.

A

return line connected at this point

returns the combined fuel back to the fuel supply

tank.

PRESSURE

ADAPl

ASSEMBLY

-ER

FUEL INLET

VALVE^\^'

SEAT

PINTLE

Ty

Z

FIGURE

12.

INJECTOR NOZZLE AND
HOLDER ASSEMBLY

Nozzle Spray Pattern

A

suspected nozzle can be checked in the field by
removing
high pressure line. The spray pattern (Figure
be observed as the engine is cranked.

WARN,NG

let the nozzle high-pressure fuel spray against skin
surfaces.

it

from theengineand reconnecting

Fuel penetrafion of the skin might
causesevere personalinjury.

it

to the

13)

Do

can

not

Cleaning

sure the work area and equipment are exceptionally clean.

A

is

the most important part

of

nozzle maintenance. Make

second method for determining a misfiring nozzle
is to remove'the exhaust manifold, run the engine,
and observe the exhaust ports for the following
conditions:

Heavy Load

-

Black smokey exhaust from any one

cylinder could indicate poor nozzle condition.

Light

or

No

Load

-

Blue/white smoke from any one

cylinder could indicate poor nozzle condition.

Adjustment:

To adjust the opening pressure, remove
each nozzle from the engine. Remove the plug from
the center of the cap nut and loosen the cap nut.

Install the nozzle to be tested on a static fuel nozzle
testing fixture (may be purchased from Onan). Fol­lowing the instructions on the tester, adjust the open­ing pressure to

1750

psi

(12,075

kPa) by turning the
adjusting screw. Clockwise increases the pressure
and counterclockwise decreases

it.

Do

not try to

adjust the pressure without a testing fixture.

Disassembly:

When removing and disassembling
nozzles, separate and label all components of each
nozzle. Never interchange components between
nozzles.

1.

Remove each nozzle assembly from engine and
remove fuel inlet and return lines.

2.

Clamp nozzle holder body

in

a vise and remove

nozzle cap nut and nozzle.

3.

Install nozzle cap nut loosely to protect lapped

surface for the holder body.

4.

If necessary to disassemble the nozzle further,
reverse pressure adjusting screw and lift out

spring and spindle assembly.

Do

not attempt to disassemble the

nozzles or adjust nozzle pressure

without the proper test equipment.

A

nozzle pressure

tester is essential to do a satlsfactorylob.

*

25

The cleaning procedure (Figure

Redistribution or publication of this document, 

by any means, is strictly prohibited.

disassembling injection equipment. Always rinse
before reassembling.

14)

is extremely Important when

in

clean fuel

Injection Nozzle Tester

Testing and adjustment can be performed only with a

15.

Do

nozzle tester, Figure
ble the nozzles or adjust nozzle pressure without the
proper test equipment.

Opening pressure, leakage and spray pattern can be
checked using the tester. If any of the above malfunc­tions appear (except opening pressure), the nozzle
valve and seat can be inspected with a magnifying
glass for erosion, scoring, etc. If cleaning with solvent
does not correct the malfunctions, a new nozzle tip
will be required. Theopening pressure can then beset
and spray pattern checked.

1.

Use a brass type scraper tool to remove hard carbon

deposits from nozzle body valve seat.

not attempt to disassem-

4.

Clean nozzle valve and polish with tallow and a
wooden polishing fixture. Take care to remove all
traces of tallow when finished.

5.

Examine nozzle valve and body with a magnifying

If

glass.
renew the valve and body.

erosion and scoring conditions are found,

2.

After scraping the carbon, polish the valve seat by
using a round pointed stick dipped in tallow.
Polishing should restore seat to its original finish

unless it’s scored.

3.

Use a special hooked type scraper to clean the
nozzle pressure chamber gallery. The hooked end
of scraper is inserted into the gallery and then
carefully rotated.

FIGURE

14.

NOZZLE CLEANING

26

6.

Use a lapping plate and compound for flat lapping
of nozzle parts which depend on a lapped surface
for sealing. A figure

7.

It is essential that the nozzle body is perfectly

centered in the cap nut when reassembling nozzle.

A

centering sleere, as shown, is used for !his

purpose.

“8”

motion is used.

FIGURE

Redistribution or publication of this document, 

by any means, is strictly prohibited.

15.

INJECTION NOZZLE TESTER

NOZZLE INSTALLATION

Before installing the injection nozzles in the engine,

thoroughly clean each mounting recess.

A

dirty mounting surface could permit blow-by,

causing nozzle failure and a resulting power

1.

Install a new heat shield to head gasket in cylinder
head recess.

2. Install heat shield, heat shield gasket, second
heat shield, and nozzle gasket.

3.

Insert nozzle assembly into recess.

tip against any hard surface.

4.

Install nozzle flange and two cap screws. Tighten
cap screws alternately to avoid cocking nozzle
assembly. Tighten each to 20-21 foot-pounds (27­28

Nom).

Do

not strike

loss.

Never use hard or sharp tools, emery
paper, grinding powder, or abrasives

of

any kind or the nozzles may be damaged beyond

use.

Soak each nozzle in fuel to loosen dirt. Then clean the
inside with a small strip of wood soaked in oil and the
spray hole with a wood splinter. If necessary, clean
the outer surfaces of the nozzle body with a brass

brush but do not attempt to scrape carbon from the
nozzle surfaces. This can severely damage the spray
hole. Use a soft oil-soaked rag or mutton tallow and

felt to clean the nozzle valve.

NOZZLE REPAIR

If cleaning will not eliminate a nozzle defect, replace
the nozzle or take it to an authorized diesel service
station.

Do

not attempt to replace parts of the nozzle

except for nozzle and pintle assembly.

Assembly

Rinse both valve and nozzle thoroughly before

assembly and coat with diesel fuel. The valve must be

free in the nozzle. Lift

should slide back to its seat without aid when the

assembly is held at a 45-degree angle.

work the valve into its body with clean mutton tallow.

it

about

1/3

out of the body.

If

necessary,

FUEL SOLENOID

The fuel shutoff solenoid (Figure 16) is also referred

it

to as a governor solenoid, as
nor during shutdown. The solenoid
bracket and controls the injection pump operating
lever. When energized, the plunger pulls into the
solenoid body. When de-energized, the solenoid
spring forces the plunger out against the operating
lever to hold

it

in the fuel-shutoff position.

The solenoid has two coils. Both are energized for

pulling the plunger up. When the plunger reaches the

top,

it

opens a set of contacts, de-energizing the pull-

in coil. The other coil holds the plunger up while the

engine is running and de-energizes when the engine

shuts down.

SOLENOID

FUEL
RETURN

FITTING

-

It

over-rides the gover-

is

mounted on a

WIRE TO CONTROL

D

TO GROUND

NGER AND SPRING

GOVERNOR LINKAGE

1.

Clamp nozzle holder body in a vise.
Set valve in body and set nozzle over

2.

3.

Install nozzle cap nut loosely.
Place centering sleeve over nozzle for initial

4.
tightening. Then remove centering sleeve to

prevent

it

from binding between nozzle and cap

nut.

5.

Tighten nozzle cap nut to
Nom).

50-55

it.

ft.-lb. (68-75

21

ADJUSTMENT SCREW

AND JAM NUT

INJECTION PUMP

0

N IECTION PUMP

DELIVERY

FIGURE

16.

VALVE

CAPSCREW

FUEL SOLENOID

To

Redistribution or publication of this document, 

by any means, is strictly prohibited.

test the solenoid, check plunger operation and
current draw with 12-volt input. Current draw with
plunger up should be about 1 amp.

If

it

the

is much

greater, the contacts did not open.
The solenoid plunger should be adjusted

so

it

fully
stops injection when in the de-energized position. To
adjust the plunger length, turn the screw and jam nut
on the plunger bottom in or out. If the plunger sticks,
remove the solenoid from its mounting plate and

clean the plunger and recess in the solenoid.

PREHEATING CIRCUIT

This 12 volt battery circuit consists partly of manifold

heaters that heat the combustion air at the intake
manifold and a glow plug in each cylinder that heats

the precombustion chamber for engine starting,
Figure

wired in parallel and are controlled by a preheat
switch on the control box.

17.

The manifold heater and glow plugs are

GLOW

MANIFOLD

HEATER

.

PLUG

INJECTION PUMP REPAIR

Internal repairs on the
special tools and step-by-step procedures for dis­assembly and reassembly.

1

CAUT,ON

m

Replace with new pumps injection

pumps that troubleshooting proce­dures prove to be malfunctioning.
unauthorized repair procedures on the injection

pumps.

Refer to Diesel Starting Guide, page

Fuel injection pumps must pass stringent quality
inspections and tests with precise settings and
adjustments in order to meet Onan’s performance
and reliability requirements. Therefore,
clearly understood by the owners and by Onan ser­vicemen that tampering or inept repair attempts can
cause irrepairable damage to the pumps that will not
be covered by the manufacturer’s warranties or
exchange agreements. Contact an authorized Amer­ican Bosch Service station or Distributor for expert
repair service on the injection pumps.

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 specifications.

PSU

injection pumps require

Do

not attempt

9.

it

must be

FIGURE

17.

GLOW PLUG AND MANIFOLD HEATER

Check each heater by removing its lead, operating
the preheat switch, and touching the lead to its
terminal.

If

it

sparks, there is continuity and the heater
is working. If any components of this circuit fail,
replace them.

Do

not attempt repairs on individual
components. If there is still a question, check the
component for heating.

FUEL

The diesel is equipped with the model

INJECTION PUMPS

PSU

fuel injec-

tion pumps.
The fuel injection pumps are constant stroke, lapped

plunger type and operated by the engine camshaft.
They deliver an accurately measured quantity of fuel
under high pressure to the injection nozzles.

A constant bleed check valve is furnished with all PSU pumps. The
bleed valve automatically bleeds off a restricted amount of fuel,
fuel vapors, and small quantities of air to prevent air accumulation
In the fuel sump area of the pumps. This valve should open at
pressures between

0.9

and

3.0

psi

(6.2

and

20.7

kPa).

PSU INJECTION PUMP

The PSU injection pump (Figure 18)
4-cylinder water-cooled diesels.

FIGURE

18.

PSU INJECTION PUMP

is

used on Onan

28

OPERATING

Redistribution or publication of this document, 

by any means, is strictly prohibited.

LEVER

I

PSU

Pump Operation

The pump face gear mates with and is rotated by a
drive gear on the engine camshaft, Figure

19.

The
face gear, pilot ring, and the reciprocating plunger in
the pump are rotated continually to assure positive
fuel distribution. The plunger is reciprocated up and
down by a multi-lobed cam on the camshaft which
bears against a tappet assembly on the pump.

Pump Cutaway View

The cutawayview in Figure 20shows the control unit
operating lever, metering sleeve, delivery valve, plun­ger and drilled passages to the plunger and injection
lines.

PUMP TAPP

FIGURE

CAM GEAR

19.

INJECTION PUMP TO
CAMSHAFT RELATIONSHIP

HYD RAULlC

A

timing button of very precise thickness transmits
motion from the tappet to the plunger and adjusts
plunger timing for the fuel pumped to each injector
during operation. Plunger reciprocation and rotation
are

so

phased that only one fuel injector is served
during theaffective portion of each plunger up stroke.
The high hydraulic pressure developed is required to
open the pressure operated fuel injector nozzles
which inject the fuel in afine mist into the combustion
chamber. Fuel delivery control, full load, and shutoff
are regulated by

the

up-and-down movement of the
fuel metering sleeve. The sleeve is controlled by the
operating lever on the outside

of

the pump. Fuel is
injected only during the high velocity portion of each
plunger up stroke.

OUTLET

0

PE

L

HY

FIGURE

20.

PSU PUMP (CUTAWAY

29

1

i

TIMING BUTTON

VIEW)

PLUNGER

METERING

\

-EEVE

SI

When the tappet slips off each lobe of the camshaft,

Redistribution or publication of this document, 

by any means, is strictly prohibited.

the spring loaded plunger is forced down opening the
fuel supply port to the fuel sump. This allows fuel

under low pressure from the transfer pump and fuel
sump to fill the cavity between the top end of the
plunger and the delivery valve. The plunger is then
ready for the up stroke.

Metering Sleeve Operation

The metering sleeve is positioned by the operating

lever

of

the governor control
eccentric pin on the end of the control shaft engages
a slot in the metering sleeveso that aslight rotation of
the control shaft causes the sleeve to ride up or down
on the plunger. As the camshaft and face gear rotate,
the drive key and a vertical slot in the face gear
transmit rotation to the plunger. Rotating the plunger
aligns the plunger outlet groove with the proper
injection line outlet for the injector to be fired on each
pump stroke.

unit,

Figure

21.

An

Preservative oil applied to the new

injection pump during assembly may
cause the pump to stick. Forcing the plunger or gear
will damage the pump. Dissolve preservative by soak­ing pump in clean filtered diesel fuel for

75

to

30

minutes.

TIMING BUTTON CODE

The timing button has a code number or letter

it

stamped on
thousandths of an inch. See Table

that corresponds to its dimension

I.

Figure

22

the timing button. One button will provide the correct

port closing.

in

shows

F

FIGURE

21.

METERING CONTROL

ECCENTRIC PIN

SLEEVE

-

TABLE

1.

FACE
GEAR

TIMING

FIGURE

CODE LETTER

STAMPED ON SIDE

22.

TIMING BUTTON CODE

OR

NUMBER

TIMING BUTTON THICKNESS

Injection pump kits include a pump and four buttons
which will time most of the engines. The button and
retainer ring are not assembled.

The injection pump on each engine must be timed to
that engine by using a timing button of specific thick-

ness. Each new pump has its port closing dimension

stamped on the pump mounting flange. The port clos-

ing dimension is measured at the factory using a
number

17

or standard button.

Pump timing is critical. use one of the two timing
methods to determine correct new button thickness.

If the correct button

ment pump refer to Table

is

not supplied with the replace-

1

and order the correct one

from your Onan dealer.

L

BUTTONS

I

NO.

I

I

C

Inch

Code

16

or

15

or

14

or

13

or

12

or

Part

S

R

P

147-01
147-01 89 .125

N

M

147-01 90

88

e

rnrn

I

Code

I

Part No.

I

147-01 51

30

Inch

Size

I

rnm

2.794

2.71

2.642

Code

~

6orF

or

7

8

or

9orK

8

10

or

H

L

I

Part

No.

147-01 52
147-01 53
147-01 54

55

147-01
147-01 56

-

.lo1

.098
.095
,092

-089

2.565

2.489

2.413

2.337

2.261

I

TIMING

Redistribution or publication of this document, 

by any means, is strictly prohibited.

INJECTION

PSU

OR

MODEL

PUMPS

50

One of two methods can be used to determine the
proper timing button to time the fuel injection pump
correctly to the engine.

Method 1 Timing

by

Calculation

This procedure is used, when all dimensions are
available for replacing an old pump, before the pump
is installed. Timing by calculation requires the port
closing dimension and button thickness from the
pump being replaced.

It

also requires the port closing
dimension of the new pump. Put the dimensions in
the PORT CLOSING FORMULA, and calculate the

new button thickness. After determining the timing
button thickness, find the button code in Table

If

injection pump is removed from the engine, make

1.

sure the steel shims between pump and cylinder

block mounting remain the same. These shims main-

tain proper gear backlash.

Do

CAUT,ON

LZx

not change the pump mounting

shim’s total thickness or the proper

pump gear to camshaft gear mesh will be affected.

The shim’s thickness is established at the factory
during engine assembly and does not change unless
a new cylinder block is installed.

Port Closing Formula:

The formula for determining
the proper port closing (PC) timing button for a new
or replacement pump is as follows:

1.

Remove old pump.

Add dimension on

3.

old

pump flange to timing but-

ton dimension. See example.

Example:

Port

closing dimension

Button thickness

Port

closing dimension

Required button thickness

Subtract port closing dimension given on new

4.

of

of

old pump 1.109 (28.169)

old

pump

of

Total 1.216 (30.887)

new pump -1.094 (27.788)

of

new pump .122 (3.099)

Inches

+

-107 (2.719)

pump flange from total dimension for old pump.
Use dimension calculated to select new timing

5.

button that is nearest the calculated dimension.
Install new timing button in pump and install
tappet on pump.

Install injection pump. Refer to

6.

lNJECT1ON

INSTAL LA TION.

MAXIMUM

THROTTLE

STOP SCREW

CODE STAMPED

ON THIS FLANGE

O-RING KEEPS

IN DURING HA

II

----+

BUTTON

(mm)

PUMP

2.

Determine port closing dimensions and original
button thickness from old pump.

A. Write down port closing dimension given on

old pump flange and port closing dimension
given on new pump flange. See example.

B.

Use a pair of channel lock pliers or screw­driver to remove tappet, retaining ring, and

timing button from old injection pump (Figure

23).

Use number or letter code on timing but­ton to obtain dimension of old timing button
from Table

1.

This code should be the same as

the code number stamped on injection pump

(Figure

rn

23).

CAUT,ON

OnallPSUpumpsbesureto

hold the pump drive gear
securely to the pump body when removing
the tappet.

If

not, the pump will come apart
and be difficult to assemble. The metering
sleeve will drop off the plunger if the gear and
plunger are removed. If the plungerport is not
enclosed by the sleeve, there will be no fuel
delivery and the pump will not operate.

TAPPET

23.

TAPPET REMOVAL

Method

GROOVE

FIGURE

2

Flow

/

Timing Injection Pump

This procedure is used when dimensions from old

pump are lost or a new cylinder block is installed.
Clean diesel fuel is used when flow timing to deter­mine if the proper timing button has been installed.

If the pump is removed from the engine, be sure the
steel shims between the pump and the cylinder block
mounting are the same. These shims maintain proper

gear backlash. The number stamped on the cylinder

block injection pump mounting pad indicates the
proper shim thickness. This thickness does not
change when a new pump is installed. It changes only

when a new cylinder block is installed.

31

1.

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Install

No.

12

timing button in new injection

pump. Remove delivery valve cap nut and holder,

take

out

spring, and replace valve holder and cap

nut (Figure 24 and 25).

DELIVERY VALVE

I

CAPNUTGASKET

\

RETURN LINES

(SHADED)

,3’f

‘f’

/

-

----=

PZSLN FLEXIBLE LINE)

CONNECT

FUEL RETURN

HERE

LINE

PUMP

CAP NUT

FIGURE

GASKET

24.

LATE MODEL DELIVERY VALVE ASSEMBLY

VALVE SPRING

CAP SCREW

u

5.

Rotate flywheel clockwise (when facing front of

Ab42--1

FIGURE

26.

FUEL LINE

TO

INJECTORS

engine [Figure 271 to point where PC mark on
flywheel is about

15

degrees (1.25 to

1.50

before timing pointer on gear cover (compres-

sion stroke of

No.

1

cylinder).

Make sure that both rocker arms on number one
cylinder are free to move indicating thevalves are
c

I

osed.

If fuel tank is disconnected, use a separate con­tainer of fuel and connect a short fuel line
between the transfer pump inlet and the fuel con­tainer. The pump has enough suction to pull fuel

out of the container.

Ignition of fuel might cause

by fire

or

cigarette,

I

serious personal injury

explosion.

or

other igniter near the fuel system.

Do

not permit any flame,

or

inch)

death

FIGURE

2. Install new injection pump. Refer to

PUMP

3.

Remove

25.

EARLY MODEL DELIVERY VALVE HOLDER

INJECTION

INSTALLATION.

No.

1

injection line. Install

No.

line with top end of line in pump outlet. Place an
open container under open end of
line (Figure

26).

No.

4. Disconnect governor linkage at ball joint and
hold control arm up at maximum fuel position.

1

injection

1

injection

32

P.C. (PORT CLOSING)

A079-5

FIGURE

27.

REAR

PORT

VIEW

CLOSING

POSITION

6. Manually operate fuel transfer pump (Figure 28)

Redistribution or publication of this document, 

by any means, is strictly prohibited.

until fuel, free of air, flows from open end of

No.

injection line into container (Figure 26)-

1

B.

Measure distance

in

tenths (or mm) from PC

mark on flywheel to point of actual port clos-

ing found in Step

7.

WORK TRANSFER PUMP

PRIMING LEVER UNTIL

FUEL FLOWS INTO

CONTAINER

ALWAYS RETURN

PRIMER LEVER TO

AUJU

Rev

FIGURE

7

28.

OPERATING TRANSFER PUMP MANUALLY

Continue operating transfer pump while assistant

LOWEST POSITION

rotates flywheel slowly in clockwise direction.
Stop flywheel rotation at exact point that fuel
stops flowing from No.
in 2 to

5

seconds is allowed). This point is the

I

injection line (one drop

injection pump plunger port closing, regardless
of flywheel position.

Timing is correct

if

port closing occurs when PC
mark on flywheel aligns with timing pointer (Fig­ure27).

If

the marks do not line up, timing is either
early or late and the timing button must be
changed.

If Step

7

indicates port closing is incorrect (lateor

early) proceed as follows (See Examples):

Multiply distance measured times

C.

.003

(-076 mm) to determine the difference in

thickness required for new button.

One degree of crankshaft rotation equals the 0.1-inch
graduation or .OO&inch button thickness for timing.

1.

Example

(7.6 mm) measurement (3
.229 mm]).

Since

button thickness, the installed button is too
inch (0.229 mm). This means a button

mm) thickerthan the one installed is required
closing
er when fuel flow stops.

Example

(10.2 mm), multiply

0.305 mm). In this case, a button .012 inch (0.305 mm)
thinner than the one installed is required.

D.

After determining which timing button is

The port closing time is /ate by 0.3-inch

0.1

inch (2.54 mm) equals .003 inch (.076 mm)

so

PC

mark on flywheel alignsat the timing point-

2.

If

PC

x

.003" = .009"

timing is too ear/y by 0.4-inch

4

x

.003 = .012 inch (4 x .076 mm

[3 x .076

thin

.009

inch (0.229

to

time port

required, remove injection pump and install
the correct button.

Install new injection pump with No.

8.

1

injection

line connected to injection nozzle.
On early model (Figure 25) injection pumps,

9.
remove capscrew and install valve spring and
capscrew with gasket. Torque capscrew to
89 ft.-lb. (102 to 120 Nm).

inch

in

by -009

75

to

=

=

A.

Mark flywheel in

tions (about five marks each direction) from

PC mark for calculating required change in
button thickness, Figure 29.

POINTER

EXAMPLE

1

FIGURE

FLYWHEEL

FRONT SIDE

29.

0.1

inch (2.54 mm) gradua-

?OINTER

TIMING

EXAMPLE

MARKS

2

33

10.

On late model (Figure 24) injection pumps
remove delivery valve capnut and holder to install
spring. Before installing delivery valve spring
push delivery valve back onto its seat using your
little finger. Install spring and valve holder.

If the spring is not seated prop-

erly the valve holder can be
tightened on/y about one-fourth of the way down.
When the spring

is

properly seated the valve
holder can be tightened about three-fourfhs of
the way down by hand. Make cerfain that the
spring is seated properly in the valve holder and
on the delivery valve before torquing.

Torque valve holder to

70

to 75 ft.-lb. (95 to 102

Nm). Loosen valve holder and retorque to

(88

ft.-lb.
with gasket to
Loosen capnut and retorque to
to

88

to 95 Nm). Install and torque capnut

50

to

55

it.-lb.

60

(70

to

to

65

Nm).

75

ft.-lb.

65

to 70

Nm).

(81

INJECTION

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Be sure the steel shims between the pump and the

cylinder block mounting are the same. These shims

maintain proper gear backlash. The number stamped

on the cylinder block injection pump mounting pad

indicates the proper shim thickness. This thickness
does not change when a new pump is installed. It only
changes when a new cylinder block is installed.

1.

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

pointer on gearcase (Figure 27). Rotation clock­wise also takes out all gear backlash in that
direction.

PUMP

PC

mark on flywheel lines up with timing

INSTALLATION

3. With injection pump drive gear locked, place
pump in mounting hole. Hold pump firmly against

cylinder block.
that the pump and camshaft gears are meshed

(Figure 31).

A

slight spring pressure indicates

Look into injection pump mounting hole to verify
that one intake lobe points outward and down
degrees.

2.

Remove screw (Figure
pump. Rotate drive gear until a 0.125 inch (3.175
mrn) brass rod can be inserted into drive gearslot.

This locks the gear in position, when installing

injection pump on engine.

ROTATE GEAR UNTIL BRASS
SLIPS INTO PLACE, LOCKING GEAR

ROD

30)

on side of injection

45

MOUNTING

m

ENGINE

CAMSHAFT

4.

If gears mesh, secure pump using a flat washer,
lock washer, and nut on each stud. Torque nuts
evenly to

/

FIGURE

15

1

Lf'

..I I,

7,

IVlUL

I

I-LUPC

CAM GEAR

31.

PUMP

to 16 ft.-lb.

I

nnr

INSTALLED

(20

to 22 Nm).

PUMP

FIGURE

30.

LOCKING THE DRIVE GEAR

ROD

34

5.

Remove brass rod and install timing hole washer
and screw.

DELIVERY VALVE FUNCTION

Redistribution or publication of this document, 

by any means, is strictly prohibited.

BLEEDING FUEL SYSTEM

The delivery valve maintains 300 to

4140

kPa) line pressure in the injector lines with the

600

psi

(2070

to

engine running, Figure 32.This pressure increasesto
about 1900 psi (13110 kPa) on each stroke of the
injection pump plunger. The trapped fuel is held

in

the lines at all times, even though the pressure bleeds
off during shutdown periods. When the lines are full of
fuel, onlyacoupleturnsof thecrankshaft are required
to build up enough line pressure for firing the

injectors.

SPRING

\

DELIVERY VALVE

.

SEAT

Bleed fuel system wheneverthe filters are changed

when there is air

in

the lines.

or

Procedure:
Manually actuate fuel transfer pump until air bubbles

are all out and clear fuel flows from the bleed valve
automatically, Figure 33.

If

the transfer pump
will not operate the pump. Rotate the flywheel one revolution
before operating the priming lever.

cam

lobe

is

on the high side, the priming lever

BLEED VALVE

CONNECT

FUEL RETURN

FIGURE

-INE PRESSURE

DELIVERY VALVE CLOSED - PLUNGER DOWN

32.

LINE

FIGURE

11

33.

BLEEDING FUEL SYSTEM

35

Oil

Redistribution or publication of this document, 

by any means, is strictly prohibited.

'Onan diesel engines have pressure lubrication to alp

working parts of the engine. The oil system includes
an oil intake cup,
valve, a full-flow oil filter and passages and drillings
through the block for oil delivery.

;

Figure

A

thin film of oil from the crankcase IubricateS the
cylinder walls and the rings wipe the excess oil off to
prevent passage of oil to the combustion chamber.

The upper portion of the cylinders are partially

lubricated by the fuel. The connecting rod bearings
are critically
high pressures and high rotating speeds. Bearing
lubrication and cooling are very important to the life
of an engine.

Normal
higher when the engine is at operating temperature. If
pressure drops below 20 psi
speed, inspect the oil system for faulty components.

System

a

gear-type oil pump, a by-pass

36

shows the pressure oil system.

in

need of lubrication because of the

oil

pressure should be 25.psi (172.5 kPa) or

(138

kPa) at governed

BY-PA
VALVE

FIGURE

36.

OIL

PRESSURE

-FILTER

LS-1013

SYSTEM

OIL

PUMP

The oil pump is mounted on thefront of the crankcase

behind the

gear.

The pump draws oil from the crankcase and delivers it
through the
through the crankcase to the crankshaft bearings,

camshaft front bearing, crankshaft passages to con-

necting rod bearings and connecting rod passages to

piston pin bushings.

gear

'Over

and

is

driven

oil

filter to the rocker housing, drillings

by

the

crankshaft

Rem oval

1.

Remove gear cover and oil base. (See

DISASSEMBLY.

2. Unscrew intake cup from pump.

3.

hemove crankshaft lock ring and gear-retaining
was her.

4.

Loosen two cap screws holding pump and the intake cup on the pump
remove pump.

ENGINE

Repair

Except for the gaskets, component parts of the pump
are not individuallv available. If the Dump is defective
or excessively worn, replace
pump by removing the two cap screws holding the
pump cover to the body. Inspect forexcessive wear
gears and shafts.

adjust the gear end clearance by changing the gasket
thickness between the pump body and cover. Use the
thinnest gasket that permits free movement of the

pump shafts. Oil all parts when assembling the pump.

To

improve pump performance,

it.

'Disassemble the

Installation

Before installing, fill the pump intake and outlet with

oil to be sure it is primed. Mount the pump on the

engine and adjust the 0.005-inch (0.127 mm) lash

between the pump gear and crankshaft gear. Mount

so

it

bottom of the crankcase.

is parallel to the

36

in

I

BYPASSVALVE

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Located on the outside of the rear bearing plate, the

37)

bypass valve (Figure

controls oil pressure
allowing excess oil to flow directly back to the crank­case. Normally the valve begins to open at about 25

psi (172.5 kPa).

It

is

non-adjustable, and normally

needs no maintenance.

To

determine

plunger sticking closed,

if

high oil pressure is caused

or

low oil pressure

plunger sticking open, clean and inspect the valve.

To

remove the valve, unscrew the recessed plug
rear bearing plate and lift out the spring and plunger
assembly. Determine proper valve operation by
checking the spring and plunger against the given
values:

by

by

in

by

the
the

the

REAR

BEARING

OIL BYPASS

OIL BYPASS

Plunger Diameter..

....

0.3365 inch to 0.3380 inch

Spring (8.5471 to 8.5852

Free Length

2.225 Ib. 0.11

(1.01 kg)

.........

(0.05

AREA

(See Note

2-5/16 inches, + 1/16 inch

(74.613,

Ib.

at 1-3/16 inches (compressed)

+

1.588

kg) at (30.163 mm) (compressed)

CYL. HEAD

3

AND

4

I

1)

4

CYLINDER

mm)

mm)

CYL. HEAD

I

AND

2

(See Note

-

FIGURE

I)

37.

BYPASS

Note1 -Usea#70drill bit (.028in. [1.17
mrn]) for cleaning being careful not to
enlarge hole. These are restricted flow
fittings.
will receive excess oil. If holes are plug­ged, valve train will run dry and wear out.

Note 2
being careful not to enlarge hole. It is
critical that fittings be kept open.
restriction is plugged, injection pump
tappet, bottom, and plunger will wear
out.

VALVE

If

holes are enlarged, valve deck

-

Use a

#56

drill bit for cleaning

If

FLUSH ROCKER BOX OIL LINE

WITH FUEL AND CLEAN HOLES

WITH FINE WIRE.

FIGURE

38.

CLEANING ROCKER

INJECTION

PUMP PAD

BOX

OIL LINE AND RESTRICTION ORIFICES

37

OIL LINES

Redistribution or publication of this document, 

by any means, is strictly prohibited.

At overhaul time the rocker box oil line should be

flushed with fuel, and a fine wire used to clean the

small holes, Figure

four cylinder engines.

Clean out all other oil lines and drillings with com­pressed air whenever the engine is disassembled or

overhauled. Reach the oil gauge passsage by re-

moving the oil filter mounting plate.
External oil lines, the rocker box oil line, and the

internal oil line to the rear bearing are replaceable. If

damaged they should be replaced.
Restriction orifices are placed

to regulate the quantity of oil delivered to the injec­tion pump gearing and tappet and to the rocker arm
and valve train areas. Two orifices are located
Tee fitting at the injection pump, and one orifice is
located

tion, ensure that all restriction orifices are kept open.
Cleaning can be done using a fine wire or drill bit and

compressed air.

in

the inlet fitting to each cylinder head.

0.028

0.046 inch size at Tee (1.17 mm)

38.

Clean standpipe breather on

in

the external oil lines

in

inch size at heads (0.71 mm)

To

prevent injection pump

train damage from lack of lubrlca-

or

valve

the

CRANKCASEBREATHER

Late model ‘engines are equipped with a crankcase
breather pipe that vents crankcase fumes directly
from the rocker box coverto the cylinder head intake
port. The crankcase breather pipe must be cleaned
after every500 hours of engine operation by inserting
a soft wire (Figure 40).

RDJC Spec

breather pulsation damper that serves two major
functions.
the intake manifold and contribute to oil carryover. It
also acts as an oil separator to condense oil vapor and
small oil droplets to prevent them from getting into
the intake manifold and combustion chamber and
causing excessive coke deposits in the valve ports.

To

disassemble, remove the breather cap from the
breather tube. At the same time, pull the baffle out of
the breather tube and clean

S

engines use a breather system with a

It

dampens pulsations which originate

it.

ROCKER COVER

in

fi

M’/

OIL FILTER (Full

The oil filter is mounted on the filter plate at the left
side of crankcase (Figure39).
every200 hoursof normal operation. Remove filter by
turning. counterclockwise, using a filter wrench.

Install new filter finger-tight plus 1/4 to 1/2 turn.

rW=)

Keep fingers and hands clear when removing the
filter and wear protective clothing.

Flow)

It

requires replacement

Hot crankcase oil can cause burns if

’

it is spilled

or

splashed on skin.

011

/

CYLINDER HEAD

FILTER

RDJC

SPECIFICATION

S

ONLY

OVERFLOW

BREATHER TUBE

TUBE BAFFLE

OIL DRAIN

FIGURE

39.

FULL FLOW OIL FILTER

38

FIGURE

40.

CRANKCASE

BREATHER

Governor

Redistribution or publication of this document, 

by any means, is strictly prohibited.

System

.The purpose of the engine governor is to maintain a
constant engine speed during changes in
demands. A governor responds to changes in power
demands by varying the throttle position. A constant­speed governor is standard on industrial engines.

GOVERNORS

-

I

he constant-speed governor (Figure 41) maintains
engine speed up to 2400-rpm. The speed-sensing
device is a ball and cup mechanism on the camshaft
gear. A yoke, resting on the cup, is connected to the
governor arm which, in turn, is connected to the
Ihrottle lever. Any change in engine speed is
transmitted from the cup to the yoke, and on to the
throttle.

'Tension on the governor spring determines thespeed

A

at which the engine is governed.
the spring is used to varythenumberof effective coils
for getting the desired sensitivity-the speed drop
from

no

load

to full load.

stud screwed into

power

Maintenance:

freely through its entire travel. Periodically lubricate
the ball joints with graphite. Also, inspect the linkage
for binding, excessive slack, and wear.

Testing and Repair:

access to the governor cup and other internal gover-

nor parts is covered
section. External service and repair is limited to
testing spring tension and checking ball joints.

To

test spring rates, use aspring-type scale. Compare

the measured rates with those in Table 2.

TABLE

Engine Governor Spring Spring

Model

RDJF

The linkage must be able to move

Removing the gear cover for

in

the

2.

GOVERNOR SPRING

1

Type

Constant

1

ENGlNE

Number

150-1084

DISASSEMBLY

DATA

1

L:zh

3.0

(76.2

I

in.
mm)

69

(12.09

Rare

4

Ibs/in

N/mm)

8435

FIGURE

DECREASE

SENS ITlVlTY

41.

GOVERNOR ASSEMBLY AND ADJUSTMENTS

39

ADJUSTMENTS

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Speed Adjustment:

change the spring tension by turning the governor
spring nut (Figure
spring tension) to increase
counterclockwise to reduce governed speed. Hold a
tachometer against flywheel cap screw.

Sensitivity Adjustment:

(no load to full load speed droop) turn the sensitivity

adjusting ratchet accessible through a covered
access hole on the side of the blower housing.

Counterclockwise gives more sensitivity (less speed
drop when full load is applied), clockwise gives less
sensitivity (more speed drop). If the governor is too

sensitive, a rapid hunting condition occurs (alternate

increasing and decreasing speed). Adjust for max-

imum sensitivity without hunting. After sensitivity

adjustment, the speed will require readjustment.

After adjusting the governor, secure speed stud lock

nut.

Excessive droop may be caused by engine misfiring. Correct this

condition before adjusting governor.

To

change the governor speed,

42).

Turn the nut clockwise (more

RPM

To adjust governor sensitivity

and

TURN NUT

COUNTERCLOCKWISE

TO DECREASE SPEED

GOVERNOR SPRING

NUT

GOVE

SHA

TURN RATCHET CLOCKWISE

To

DECREASE

t347'J

SENSITIVITY

TURN RATCHET COUNTER­CLOCKWISE TO INCREASE
SENSITIVITY

WARN,NG.

a

Contact with rotating machinery

might cause serious personal injury
or death. Stay clear of rotating components and
ensure that protective shields and guards are in place
and secured before operating machinery.

FIGURE

42.

GOVERNOR ADJUSTMENTS

40

Starting System

Redistribution or publication of this document, 

by any means, is strictly prohibited.

These models use a separate 12 volt starting motor

mounted on the

the flywheel.

motor with a solenoid for engaging the pinion and an
over-running clutch. When the solenoid is energized,
its core pulls
with the flywheel ring gear. At the same time, contacts
in the solenoid close to provide a circuit for the starter
motor. The starting motor remains engaged until the
starting switch is released.

If

engine is equipped with a start-disconnect switch, the starter
motor will automatically disengage flywheel gear when engine
speed reaches about

The starter is protected from over-speed by an over­running clutch which permits the engine to run faster
than the starter before the pinion is disengaged. Fig­ure

43

shows the starting circuit.

MAINTENANCE

Periodically check the starting circuit wiring for loose
or dirty connections. Inspect the starter commutator

and if it is dirty, clean with number

not use emery cloth or emery paper). Check the
brushes for poor seating on the commutator and for
excessive wear.

right

hand side of the engine to drive

It

is a standard automotive starting

in,

shifting the pinion into engagement

900

rpm.

00

sandpaper (do

If

starting motortests are required, remove the motor

from the engine and test

it

on a bench. Test the free-

running voltage and current.

TESTING

Poor cranking performance can be caused by afaulty
starting motor, defective battery, or high resistance in
the starting circuit.

Check the charge condition of the battery with a

hydrometer.

Ignition
might cause severe personal injury.

Do

not smoke while servicing batteries.

Specific gravity should be between 1.290 and 1.225

75

when

percent charged. If not, recharge the battery.
Check electrolyte level. If battery will not recharge,
replace it. Keep battery connections tight and clean.

With the starting motor operating, check the voltage
drops

(1)

from the battery ground terminal post (not

the cable clamp) to the cylinder block, (2) from the

cylinder block to the starting motor frame and

from the battery positive post to the battery terminal

stud on the solenoid. Normally, the voltage drops at

(1)

and

(3)

should never exceed

under the most severe conditions (extreme cold). The
voltage drop at (2) should never be permitted to
exceed

0.3

V

under the same severe conditions. Tho­roughly clean all connections
showing excessively high voltage drops.

of

explosive baftery gases

0.6 V each, even

in

any part

of

the circuit

(3)

A712

I

FIGURE

43.

STARTING SYSTEM

Using a spring scale and torque arm, test the stall

44.

torque, Figure

Multiply the spring scale reading

by the arm length for the torque value.
If free running speed is low, and starter has a high

current draw with

low

stall torque, check for tight,

dirty or worn bushings, bent armature shaft, or loose

field pole screws, allowing armature to drag. Check

also for shorted or grounded armature and field.

A low free speed with low torque and low current
draw indicates an open field winding, high internal
resistance due to poor connections, defective leads,
broken or worn brushes, or scored, worn, or dirty
commutator.

41

I_

Redistribution or publication of this document, 

by any means, is strictly prohibited.

I2

#,.-4

FIGURE

44.

TESTING

High free speed with low developed torque and high

current draw indicates shorted fields. Since there is

no easy way to detect shorted field coils, replace and

check for improved performance.
The voltage drop across the solenoid on the starting

motor should be less than

0.3

volts. If not, remove it

for repair.

BATTERY

Engines with a separate cranking motor normally use
a single 12 volt battery of at least 62 amp-hour
capacity.

The battery charging system maintains the batteries
at or near full charge at all times. Inspect the battery
charging system and adjust the charge rate if batteries
appear to be continually discharged.

Adding accessories that draw battery current requires an adjust-

ment

of

the charge rate.

If discharge or failure to charge cannot be traced to

the battery charging system, thoroughly inspect and
test the battery,’and replace

it

as necessary.

REPAIR

Armature:

defects before checking for grounds or shorted coils.
To test for grounds, use a 12 volt test lamp and check

between each segment of the commutator and the
shaft. Do not touch probes to the commutator brush

surfaces, as this will burn the smooth surfaces.

A

growler is necessary to test for shorted coils. With
the armature
armature surfaces. If a coil is shorted, the steel strip
will become magnetized and vibrate. Rotate the
armature slightly and repeat the test. Do this for one
complete revolution of the armature. If the armature
has a short or ground, replace

If the commutator is only dirty or discolored, clean

with

00

motor after cleaning. If, however,

or

worn, turn

Inspect the armature for mechanical

in

the growler, run a steel strip over the

it.

or

000

sandpaper. Blow the sand out of the

it

is

scored, rough

it

down

in

a

lathe.

it

STALL

TORQUE

Field Coils:

Using a test lamp and probes, check the

field coils for grounding to the motor frame or open

circuit. Inspect all connections to be sure they are

properly clinched and soldered. Inspect the insula­tion for evidences of damage. The only way to check
for field coil shorts is to use the starting motor test.

Bearings:

If either the front or rear bearings show
excessive wear, replace them. Drive the old bearings
out, and using an arbor press and the proper arbor,
press new bearings into place.

Brushes:

Check the brushes for wear or improper

seating. They should slide freely in their holders.

Check the brush spring tension with a spring scale.

To change spring tension, twist the spring at the

holder with long nosed pliers.
Replace Prestolite brushes when excessively worn,

or when worn to

5/8

inch in length. Replace Mitsubishi,
brushes when excessively worn or when worn to 7/16
inch in length. Some brushes are soldered to the field

coil. To remove these brushes, unsolder the lead and
open the loop in the field coil lead. Insert the new
brush pigtail completely into the loop and clinch
before resoldering.

A

good soldering job is necessary
to ensure good contact and low voltage drop across
the connection.

Over-running Clutch:

but do not dip in solvent.

Clean the clutch thoroughly

It

cannot be repacked with

grease.

It

should slide easily on the armature shaft with no
binding. Turn the pinion, it should rotate smoothly,
but not necessarilyfreely. Reverse the direction afew

times and

it

should instantly lock and unlock. Replace

the clutch if operation is defective or pinion is worn or

damaged.

Shifting Solenoid:

in

the coil. Check pull-in coil continuity between the

See that the plunger moves freely

solenoid control terminal and the solenoid connection
to the motor. Check the hold-in coil continuity

between the solenoid control terminal and ground on

the motor.

42

SHIFTING

Redistribution or publication of this document, 

by any means, is strictly prohibited.

SOLENOID

/

SOLENOID

PLUNGER

FIGURE

PRESTOLITE STARTER REMOVAL

AND

10.

DISASEMBLY

1.

Remove connections to controls and battery at
shifting solenoid. See Figure

2. Remove nut-holding rear mounting bracket to
engine.

3.

Remove three cap screws holding starting motor
flange to engine and pull out motor.

4.

Remove link

pin

holding the shift levertosolenoid

plunger and.remove shift lever center pin.

5.

Remove through bolts from commutator end of
motor. Pull off end cover and lift brushes off their
seats.

6. Pull pinion housing from front end of motor and
lift armature and clutch out of motor frame.

7.

To

remove over-running clutch from armature,

drive retainer away from lock ring near front end

of shaft, remove lock ring and pull assembly off.

Do

not attempt to disassemble clutch assembly.

8.

If necessary to service solenoid, remove four cap

screws and electrical connection holding

motor frame. Remove two screws on rear of

solenoid to reach switch contacts.

9.

Mount starter motor to engine by adirect reversal

of the removal procedure (Figure

battery cable and wires to starter.
Connect battery cables to battery. Connect

ground cable last.

45.

46).

it

Connect

45.

to

STARTING

MOTOR

FIGURE

46.

STARTING MOTOR FLANGE

PRESTOLITE STARTER ASSEMBLY

Before assembling, soak the bronze bearings in oil.
They are absorbent bearings, designed to hold up to
25 percent of their own weight in oil. Be sure the felt
oil

pad is

bearing.
When the motor is assembled, check the armature

end play. It should be between 0.005-inch (0.127 mm)
and 0.030-inch (0.762 mm). Adjust end play by
adding or removing washers on the commutator end
of the armature.

in

the outer end of the commutator end

43

Before installing, check the pinion clearance. Proper

Redistribution or publication of this document, 

by any means, is strictly prohibited.

clearance is important to ensure starter engagement.
Press on solenoid core to shift the pinion into full
mesh and measure the clearance between pinion and
pinion stop, Figure 47. This should be between 0.07­inch and 0.12-inch

(3.05

mm) (as near to 0.070-inch

[1.78 mml as possible.) Adjust the link screw on the

end of the solenoid plunger for proper clearance.

PUSH

PLUNGER

STOP

i

STARTING MOTOR NEED

NOT BE REMOVED FROM

ENGINE TO MAKE

MEASUREMENT

THIS

FIGURE 47. PINION CLEARANCE

'

(0.07"-0.19"

CLEARANCE.

SEE TEXT)

THROUGH

BOLTS

%

FIGURE 47a. REMOVING REAR BRACKET

4.

Remove frame assembly, and brush holderassem­bly while pulling the brushes upward. Then re­move armature assembly.

5.

Remove cover assembly, (snap ring and washer)

from the pinion shaft (Figure 47b).

ES-1186

MlTSUBlSHl STARTER REMOVAL

AND INSTALLATION

1.

Remove both battery cables from battery. Dis­connect ground cable first.

2.

Disconnect battery cable and electrical lead wires

from starter.

3.

Remove capscrews and flat washers that attach
starter to mounting bracket.

4.

Remove starter.

5.

Mount starter motor to engine by a direct reversal

of

the removal procedure. Connect battery cable

and wires to starter..

6.

Connect battery cables to battery. Connect

ground cable last.

MlTSUBlSHl STARTER DISASSEMBLY

1.

Remove M terminal nut and wire lead from

solenoid.

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

47a).

d

ES-1195

SNAP

FIGURE 47b. REMOVING SNAP RING 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 47c).

CAPSCREW

FIGURE 47c. REMOVING CENTER BRACKET

WASHERS

COVER

RING

CENTER

BRACKET

ES-1187

44

7-

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Remove gear, spring set and leverassembly 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

not replaceable and must be replaced with the
bracket.

is

FRONT

FIGURE

WASHER

47d.

MlTSUBlSHl

SOLENOID

FRAME

ASSEMBLY

STARTER

TERMINAL

ASSEMBLY

M

BEARING

THROUGH

HOLDER

XES-1255

MlTSUBlSHl STARTER ASSEMBLY

For assembly reverse the disassembly procedure, but

note the following items. See Figure 47d.
Whenever starter motor is disassem bled apply grease

of

to each
grade; Multemp

Armature shaft gear

Reduction gear

Ball bearing (Both ends
Stopper on pinion shaft
Sleeve bearing
Pinion gear
Sliding portion of lever

Pinion Shaft End Play Adjustment

Adjust end play

0.0315

between center bracket and reduction gear (Figure

47e).

the following points. (Recommended

PS

No.

2.)

of

armature

so

that

it

is

0.1 to

0.8

mm

(0.0039

inch) with the adjusting washers placed

to

PINION

GEAR

/

FIGURE

oVERRUNNING

CLUTCH

PINION

\

47e.

ADJUSTING PINION SHAFT END

SHAFT

1

SNAP

RING

I

ES-1191

PLAY

45

With pinion gear removed, install reduction gear onto

Redistribution or publication of this document, 

by any means, is strictly prohibited.

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 Installation

Place spring and pinion gear onto pinion shaft. Slide

stop ring onto pinion shaft and install retaining ring
groove. Pull stop ring over retaining ring (Figure 47f).

I

STOP

RING

STOP

RING

in

PACKING

CENTER

BRACKET

I

I

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
47h).

LEVER

SPRING

ES-1185

FIGURE 479. LEVER INSTALLATION

,

/

SNAP

RING

ES-1194

FIGURE 471. PINION GEAR INSTALLATION

Lever Assembly Installation

Figure 479 shows the correct method of installing the
lever assembly, spring, and packing. Pay close atten­tion to direction of lever.

AMOUN

T

OF I TRAVEL

FIGURE 47h. PINION GAP ADJUSTMENT

4. The pinion gap should be

0.0787 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
washers increases clearance.

46

PINION

I

-+I

(PINION

GAP)

I

0.3

to

1

ES-1192

2.0

mm

(0.01

18

to

of

BELT DRIVEN

Redistribution or publication of this document, 

by any means, is strictly prohibited.

ING

ALTERNATOR (Optional)

(35

AMP) BATTERY CHARG-

This information is presented for field useonly. Major

repair should be done in the shop.

Brush Assembly Removal

Remove brushes as follows:

1.

Remove three screws which fasten voltage
regulator to alternator.

2.

Disconnect regulator leads and remove regulator.

3.

Remove two screws on phenolic coverand lift out
cover and gasket.

4.

Pull

brush assembly straight

5.

Reverse procedure for assembly (Figure

up

and lift out.

48).

Brush Assembly Tests

Test brush assembly as follows:

1.

Connect an ohmmeter or test lamp

(12

volts) to

the field terminal and to the bracket. The test

lamp should not light or resistance reading 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

(con

ti

nu ity).

FIGURE

VOLTAGE REGULATOR

MOUNTS

48.

OPTIONAL, BATTERY CHARGING,
EXTERNAL ALTERNATOR

HERE

47

Engine Disassembly

Redistribution or publication of this document, 

by any means, is strictly prohibited.

ENGINE REBUILDING

When engine disassembly is necessary, remove com­plete assemblies (tear down individual components

like fuel pump, breaker mechanism, etc., as bench

jobs).

Use special tools available'.

Disassembly:

1. Common sense will dictate proper order of dis­assembly. As disassembly progresses, the order

may be changed, as will become self-evident.

2.

A suggested procedure would be as follows:
a. Radiator, water pump.

b.

Flywheel-using puller or pry-bar method.

c. Gear Cover-protect oil seal from keyway

damage.

d.

Crank Gear-use puller and gear puller ring.

e. Loosen accessories such as fuel pumpsand oil

f

i

I

ter.

f. Starter motor.

g. Drain oil

h. Cylinder head.

i.

Valves, springs, rocker arms.

j.

Camshaft and gear, -rear bearing plate, oil
pump.

k. Piston, connecting rod bearings.

I.

Crankshaft.

m. Try to analyze reasons for any parts failure and

necessity of the repair.

n. Cleanliness and neat, orderly work area makes

job easier to do.

0.

Use.proper meters and gauges. Observe if

cy1

i

grinding, or if other major shop work is

necessary.

-

discard oil removed.

nder req u i res boring , cranks haft needs

Assembly (Use Genuine Onan Parts):

Engine assembly procedure is normally the

1.

reverse of disassembly
clearances of bearings, connecting rod, proper
fitting and sizing of piston, rings, etc.

Follow proper recommended procedure for fit of

2.

valves, adjusting clearances, and torque of all
special items., Use a torque wrench to assure
proper tightness without danger of stripping
threads.

As each internal engine part is assembled, use a

3.

wrench to rotate crankshaft, making certain
turns freely.
tion you then know your last step is responsible.

If

tightness is noted after any opera-

-

observing proper

it

4. As each internal engine part is assembled, coat it

6.

'

7.

8.

ASSEMBLY SUGGESTIONS ' (Things
keep in mind during engine assembly)

1.

2.

3.

4. Select proper length of any screw or bolt and

5.

heavily with oil (same grade used in crankcase).
During first few critical momentsof operation, the

engine will depend on this lubrication.

5.

After you have internal engine parts reassembled,

If

the engine should turn freely.
and attention have been given, the engine will
operate efficiently.

At this point,

outside accessory items to the block assembly.

Order

When engine is complete, install controls. Check
the tagged wires. Using wiring diagram to con-

nect leads to control, and from control to engine.
All wires are marked for correct identification. If
the unit is to work properly, wires must be

connected correctly.
The engine is now ready for testing. Follow

suggestions given on

Engines.

the engine about

reach normal operating temperature.

See Onan

require a

Some of these tools are:
a. Oil seal driver and guide, bearing driver.
b. Valve spring compressor, valve lock replacer,

c. Gear puller and gear puller rings.
d. Piston ring spreader and compressor.
e. Flywheel puller, pry.bar, armature puller.

f. Torque wrench, plastigauge (for correct bear-

g. Armature growler, gas pressure gauge

Wet holes in crankcase (holes through
crankcase) -always use copper (gasket) washers.

Nuts, bolts and screws that do not require exact
torque should be tightened snugly, then 1/4extra
turn.

position in hole. Make sure they do not
Gasket kits sometimes cover more than one

engine. Therefore, select gasket of correct size
and shape for part being used. Always use new
gaskets.

of

valve guide driver, and valve seat remover.

ing clearance).
manometer).

it

is a matter of mechanically adding

assembly is reverse

Testing and Adjusting

:Before final test and adjustments, run

15

minutes'under light load to

Tool

Catalog (900-0019) - many items

special tool

for correct installation.

reasonable care

of

disassembly.

bottom.

to

(or

$

6.

Redistribution or publication of this document, 

by any means, is strictly prohibited.

When disassembling engine,

mike

bearing plate
gasket thickness. Then select proper shim
thickness for correct end play.

Shims establish end play. Only one thickness gasket
included in kit.

7.

When assembling crankshaft, make sure bearing

thrust washers are in proper position supported
by bearing stop pins. Use cup grease to hold in
place.

8.

When adjusting valve lash, tap rocker arm
straight when checking with feeler gauge.

9.

Crank gears are easier to remove and install if
heated a slight amount.

Do

not overheat

or

temper may

be lost and shaft may expand.

so

it

is

is

Maintenance:

Check the valve clearances at regular intervals (see

SERVICEAND MAlNTENANCEsection).

In

addition,

clean the combustion chambers and valve seats as

required if engine loses power or has

low

compres-

sion.

VALVE CLEARANCE ADJUSTMENTS

The valves are adjusted cold. Afterthecooling period,

adjust
order.

To adjust valve clearance, proceed as follows:

No.

1

cylinder first and the rest

1.

Rotate flywheel clockwise until cylinder number

in

the firing

is up on acompression stroke and theTC mark on
the flywheel lines up with the timing pointer on
the gear cover, thenturn 10-45degreespastTCto

be sure lifter moves off ramp of cam.

1

.

10.

See FUEL SYSTEM section for correct engine
timing.

11.

Allow some gear lash (approximately 0.005-inch)
in oil pump. Do

not install gears tightly against

each other!

TESTING AND ADJUSTING ENGINES
Preparation

Check the following:

1.

Put proper oil

2.

Service air cleaner.

3.

Connect fuel line.

in

crankcase.

4. Connect load.

5.

Connect fully charged battery.

6.

Check ventilation for proper cooling.

OPERATION

1.

Start engine - (see

2.

Check oil pressure.

3.

Run unit

15

ternperatu re.

4. Check for oil leaks, loose electrical connections,
tight fuel lines and tight exhaust connections.

Diesel Starting Guide).

minutes to bring up to operating

In this position, both valves will be closed and the rockeranns
are free to move slightly indicating maximum clearance.

2.

Using a feeler gauge, check clearance between
rocker arm and valve (see Figure

49).

Increase or

reduce clearance until proper gap is established;
adjust with lock nut which secures rocker arm to
cy1

i

nder head.

RETAINER

-\

d

EXHAUST

ADJUSTMENTS

Adjust governor for speed and sensitivity.

IMPORTANT For complete customer satisfaction, repaint unit
(Onan Green, spray can 525-0137, or Onan White, spray can 525-

0216) and apply instructions from Kit 98-11OOC or Marine Kit 98-

1807.

CYLINDER HEADS, VALVES

Each cast iron cylinder head assembly has alloy
hard en ed -f aced valves, re
hardened inserts, guides, rocker arms, injection
nozzles and glow plugs.

I

ease-ty p e rotators, al I oy

FIGURE 49. SETTING VALVE CLEARANCES

49

To adjust valve clearance for number 2 cylinder,

Redistribution or publication of this document, 

by any means, is strictly prohibited.

3.
turn flywheel

(1/2 revolution) from position used in Step

in

a clockwisedirection 180degrees

1.

The
flywheel position should be between 10 degrees
and 45 degrees past the bottom center (BC).

IMPORTANT:

on the flywheel.

4.

After timing number 2 cylinder, adjust valve
clearance according

5.

To adjust valve clearance for number 4 cylinder,
turn flywheel

Four-cylinder engines

ta

in

a clockwisedirection 180degrees

step 2.

do

not have a

BC

mark

(1/2 revolution). The flywheel should be between
lodegreesand 45degrees past flywheel TC mark.

After timing number 4 cylinder, adjust valve

6.
clearance according to Step 2.

To adjust valve clearance for number 3 cylinder,

7.
turn flywheel in a clockwise direction

1

80 degrees
(1/2 revolution). The flywheel should be between
10 degrees and 45 degrees past BC.

After timing number 3 cylinder, adjust valve

8.
clearance according to Step 2.

Testing:

The cylinder compression test can be used to deter­mine the condition of valves, pistons, piston rings,
and cylinders.

Repair:

Thoroughly clean all components of the cylinder
head assemblies. Remove all the carbon deposits
from the intake and exhaust ports and clean all gasket
surfaces.

Valves:

burning, pitting, or a warped stem. Refinish valves
that are slightly pitted or burned on an accurate valve
grinder. Refinish intake valves to a 42 degree angle
and exhaust valves to a 45 degree angle. If they are
badly pitted or have a thin edge when refacing,
replace them.

Check refinished valves for a tight seat to the valve
seat with an air-pressure-type testing tool or by
applying Prussian Blue on the valve face and rotating

it against the seat.

Valve Guides:

See the

the proper clearances cannot be obtained by replac-

ing the valves, replace the valve auides. Drive the old

valve guides into the valve chambers. Drive new
guides in until they protrude 11/32 inch (8.731 mm)

from the rocker box side of the head. Ream the new

valve guide to obtain the proper clearance.

Remove all carbon and check each valve for

Check valve guide to valve clearance.

DIMENSIONSAND CLEARANCES

-

-

section.

If

To check compression, run the engine until thor-

oughly warm. Stop engine and remove all injection
nozzles. Insert the compression gauge in one nozzle
hole. Crank the engine and note the reading.

Compression of a standard new engine cranking at
about 300 rpm is about 350-400 psi (2415 to
2760 kPa). RDJC prior to Spec P300-350 psi (2068 to
241 3 kPa). Compression should be fairly uniform,
normally with less than 30 psi (207 kPa) difference
between the highest and lowest cylinder, taken at the

same cranking rpm.

Compression readings may deviate from the above
readings because

of

differences in cranking speed,
altitude and ambient temperature conditions. There­fore the specification is given only as a guide. The

best indication of leakage is the pressure difference

between cylinders.

Disassembly:

Keep rocker arms, rocker arm nuts, push rods and tappets in order,

so

they

go

back in the same valve train position.

1. Remove rocker box cover, fuel nozzles and
connecting oil lines to cylinder heads.

2. Remove intake and exhaust manifold.

3. Remove cap screws holding each cylinder head
to cylinder block.

4. Remove each head. If it sticks, rap it sharply with a

soft hammer.

5.

Remove rocker arms and push rods.

6. Using a valve spring compressor, disassemble the
valve assemblies.

Do

not use a pry.

Valve Seats:

If the valve seats are pitted, refinish

them. Using conventional seat-grinding equipment,

reface each seat to a 45 degree angle and a seat width
of 0.047 inch to 0.062 inch (1.19 to

1.57

mm). You

should be able to reface each seat several times

before

it

becomes necessary to replace

it.

If the valve seats are loose or cannot be refaced,
replace them.

1

Use Onan tool number 420-031

50)

ure

to remove each valve seat. Adjust the tool to

in a drill press (Fig-

cut 1/64inch (0.397mm)from theedgeoftheseat. Oil
the pilot to prevent it from seizing in the valve guide.

Cut each seat down

to

a narrow rind on edges and
bottom and break it out with a sharp tool. Be careful
not to cut into the counterbore bottom.

FROM

EDGE OF

FIGURE

50.

REMOVING VALVE

SEATS

50

Thoroughly clean the valve seat counterbore and

Redistribution or publication of this document, 

by any means, is strictly prohibited.

remove any burrs from the edges. If the counterbore

is

damaged,

seat. Oversize seats are available

inch,

0.010

0.09

mm). Otherwise, install new standard size seat

inserts.
Drive the new valve seat inserts into place. Be certain

that each seat rests solidly on the bottom of the

counterbore at all points. To make installation easier,
heat the cylinder head in an oven at 325" F (162" C) for

<

about 1/2 hour and cool the valve seats in dry ice.
Face each new seat to a 45 degree angle and a width

of approximately 3/64 inch
seat face should contact the approximate center of
the valve face. Use Prussian
check this. Make any corrections on the seat, not the

valve face.

When the new seats are installed and faced, insert the

valve into each, and check the clearance from the
valve head to the face of the cylinder head. This must
be at least

the seat.

it

will have to be machined foran oversize

in

0.002 inch,

inch and 0.025 inch (0.58,0.056,0.068. and

(1.191

BI

0.030

inch (0.762 mm). If it is not, regrind

mm). The finished

ue on each valve face to

0.005

FIGURE

Installing manifold now aligns all four exhaust ports with
the exhaust manifold before the heads are torqued down.

51.

HEAD BOLT TORQUE SEQUENCE

.

Valve

Springs:

compression scale. Valve spring data is given

DIMENSIONS AND CLEARANCES

any spring that is weak, cracked or pitted, or has ends
out-of-square.

Check thevalve springson an accurate

in

the

section. Replace

VALVE AND HEAD ASSEMBLY

Installation

Push a valve seat stem oil seal onto each intake

1.

valve guide and clamp in place. Then oil inside

surface of each seal using SAE

Oil stem of each valve lightly (SAE

2.
insert each in its own guide.

Check each valve for a tight seat with an air-

3.
Dressure tvDe tester. If a tester is not available,
make peniil marks at intervals on valve face;
observe if marks rub off uniformly when valve is

rotated part of a turn
regrind valves. After seal has been installed, do
not remove valve stem without protecting seal

from sharp edges on keeper area of valve stem.

Using a valve spring compressor, compress each

4.

valve spring and insert valve spring retainer and
retainer locks.

Install head assembly and gasket to cylinder

5.

block. Tighten head bolts to 44 to 46foot-pounds

(60-62 Nom). Follow sequence in Figure

Steps a. through

a. Tighten cylinder head bolts finger-tight.
b. Install exhaust manifold and tighten

c.

in

seat. If seat is not tight,

50

engine oil.

50

oil) and

51

and

c.

Tighten cylinder head bolts

shown

41

d. Tighten cylinder head bolts in same sequence

to 44-46 foot-pounds (60-62 Nom).

e. After 60 seconds, retighten cylinder head bolts

in

Nom). This step compensates for the com­press of the cylinder gasket.

6. Install intake manifold, nozzles, glow plugs and
oil lines.

7. Install valve stem cap.

8. Install push rods, rocker arms and rocker arm

nuts.

9.

Set valve clearance. See Figure

CAUT'oN

in

Figure

Nom).

sequence to 44-46 foot-pounds (60-62

Cylinder head bolfs

affer

ened and valve clearance

the hours

51

to 25-30 foot-pounds (34-

in

49.

must

50

sequence

be refighf-

musf

hours

be

of

INTERNAL DISASSEMBLY

If engine disassembly is necessary, observe the

following order (i.e. Flywheel, Gear Cover..

disassembly progresses, the order may be changed
somewhat as will be self-evident. The engine
assembly procedure is the reverse of disassembly.
Any special assembly instructions for a particular

group are included

reassembling, check each section for these special

assembly instructions or procedures.

in

the applicable section. When

.).

As

51

FLYWHEEL

Redistribution or publication of this document, 

by any means, is strictly prohibited.

The flywheel is a tapered fit on the crankshaft. Use a
flywheel puller (Onan tool number 420-0100) to

remove the flywheel.

part way through, then break

and heavy hammer.
To install a new ring gear, place

380°F

-

400°F (192" to 204°C) for

it

using a cold chisel

it

in

an oven heated to

30

to

40

minutes.

Loosen the flywheel mounting screw a few turns.
Place bar against the flywheel screw and attach bar,
using two 3/8-16 thread screws in the holes provided
in flywheel. Alternately tighten the screws until fly-

wheel is free.

FLYWHEEL REPLACEMENT

Replacement flywheels are supplied without the tim­ing markings because each flywheel must befitted to
its engine. The only accurate method of determining

the top dead center (TDC) and port closing (PC)

.

points is to measure the piston travel. This is a critical
measurement and should be attempted only with
accurate, dependable equipment.

Use the following procedure to locate the TDC and
PC marks on the flywheel:

With the flywheel mounted, remove the head and
install a depth gauge over the front piston. Rotate the
flywheel to find theTDC position on thecompression
stroke and mark this point on the flywheel. Next, turn
the flywheel counterclockwise until the piston drops
exactly 0.128 inch (3.25 mm). RDJC prior to Spec

0.155

inch (3.94 mm). Mark both TDC and piston

drop to PC point on the flywheel.

Ring

Gear:

To remove the ring gear, if damaged, saw

P,

Do

not heat with a torch or ring gear

may be warped.

When heated properly, the ring will fall into place on

the flywheel. If

it

does not go on all the way by itself,
drive it into place with a hammer. Do it fast and do not
damage the gear teeth. The ring will contract rapidly
and may shrink to the flywheel before it is in place. If

this occurs, a new ring gear may be required.

GEAR COVER

To

remove the gear cover, detach the uppergovernor

ball joint. Remove the

governor speed-adjustment

and governor spring bracket.
Remove the screws holding the gear cover to the

crankcase.

To

loosen the gear cover, tap it with a soft

hammer.

Governor

two sets

Shaft:

of

The governor shaft is supported by

needle bearings. To remove the shaft,

remove the yoke and pull the shaft from the gear

cover. If the shaft is binding, clean the bearings. If

loose, replace the bearings.

To

remove the larger
bearing, drive both bearing and oil seal out from the
outside of the gear cover. Remove the smaller bearing

with an Easy-Out or similar tool. Press new bearings

and oil seal into place. See Figure 52.

nut

GOVERNOR

CUP

GOVERNOR SHAFT YOKE

(Smooth side toward

'

GOVERNOR

cup)

C

FIGURE

52.

GEAR

BE SURE THAT

COVER

52

GOVERNOR ARM

OIL

ASSEMBLY

Gear Cover

Redistribution or publication of this document, 

by any means, is strictly prohibited.

or worn. Drive the
cover. Lay the cover on a board

Oil

Seal:

Replace the oil seal if damaged

oil

seal out from inside the gear

so

the seal boss

is
supported. Using an oil seal driver, insert the newseal
from the inside with rubber lip toward outside of gear
cover (open side of seal inward) and driveit flush with
the outside surface. During gear cover installation,

use the driver to protect the

oil

seal. See Figure 53.

1

WHEN GOVERNOR
PROPERLY ASSEMBLED
THE DIMENSION SHOWN

ON

DRAWING WILL BE

AS

INDICATED.-

IS

CENTER

Assembly, Gear Cover:

I

1.

Work governorshaft to check for binding and see

GOVERNOR

P

SNAP

that the governor shaft end-thrust ball is in place,

Figure 52.

2.

Turn governor yoke

so

smooth side is toward

governor cup.

3. Turn governor cup

so

stop pin

in

gear cover will fit

into one of the holes in the cup surface (Figure

52). Measure distance from end of stop pin to
mounting face of cover. It should be

(1

9.844 mm). If it is not, replace pin. Pin should be

25/32

inch

positioned with open end facing crankshaft seal.

4. Coat oil seal lip with oil or grease. Apply a piece of
masking tape over the crankshaft keyway to pro-

tect seal and install gear cover.Tighten mounting
screws to

15

to

20

foot-pounds

(20

to

27

Nm).
Before tightening screws, be sure the stop pin is
in governor hole. See Figure 53.

Repair:

FIGURE

Replace any flyballs that have flat spots or

54.

grooves. The flyball spacer is attached to the cam­shaft gear with three flathead screws. Check to see
that the spacer screws are tight. Replace the cup if the

race surface is grooved or rough. The governor cup
must be afree spinning fit on the camshaft center pin,
but should be replaced

U

GOVERNOR

if

excessively loose or wobbly.

CUP

Thecamshaft center pin extends out 3/4 inch (19 mm)

from the end of the camshaft. This distance provides

GEAR

COVER

an in-and-out travel distance of 7/32 inch
for the governor cup, as illustrated. Hold the cup
against the flyballs when measuring. The camshaft

(5.6

mm)

center pin cannot be pulled outward or removed

INSTALLOIL SEAL

FLUSH

SURFACE

WITH

THIS

without damage. If the center pin extends out too far,
the cup will not hold the flyballs properly.
tance is less than 7/32 inch

(5.6

mm), (the engine will

If

the dis-

race, especially at no load) remove the center pin and

OIL SEAL

press in a new pin.

Installation:

To install the governor assembly, tip the

front of the unit upward. Set the flyballs in their

recesses (space five balls in every other slot) and
position the governor cup on its shaft. Finally, brush

with heavy grease and install the snap ring on the

THIS SURFACE MUST

BE

CLEAN

INSTALLING SEAL

BEFORE

center pin.

PISTONS, RINGS, CONNECTING RODS

Onan diesel engines use cam-ground aluminum

pistons. Each piston is tapered and fitted with three

compression rings and an oil control ring. Full-

FIGURE

53.

GEAR COVER

OIL

SEAL

floating piston pins connect the piston

to

its connec­ting rod. The pins are held in place with a snap ring at
each end. The lower end of each connecting rod
contains half-shell precision bearings and the upper

GOVERNOR CUP

n ish ed bush

i

n

g

s.

end

,

s

e

m

i

-f

i

To remove the governor cup, remove the snap ring
from the camshaft center pin and slide the cup off. Be
sure to catch the five (some models have ten) flyballs
that will fall out when the cup is removed. Figure

54

shows the governor cup.

Some engines are fitted with
pistons at the factory. These engines are marked with an E
following the engine serial number. Use
oversize rings for these pistons.

0.005

inch

(0.127

0.005

mm) oversize

inch

(0.127

mm)

53

Removal and Disassembly

Redistribution or publication of this document, 

by any means, is strictly prohibited.

On 4-cylinder engines, the connecting rod and cap
are stamped for installation in the proper cylinder.
When removing piston assemblies, check the mark­ing

so

each can be installed in the proper cylinder.

1.

Drain crankcase oil and remove oil base.

2. Remove cylinder heads.

3. Before pushing pistons out, remove ridge at top
of cylinder bore.

4. Remove cap from each connecting rod and push

of

assembly through top

cylinder bore. Replace

cap and bearing inserts in proper assembly.

5.

Using a ring expander, remove rings from each
piston.

6. Remove two retaining rings and push piston pin
from each piston.

Cylinders

ThecylinderwalIsshouId be freeof scratches, pitting

and scuffing. Check each with an inside reading
micrometer for out-of-round and wear. RDJF bore
should measure between 3.4995 inches (88.8873 mm)
and 3.5005 inches (88.9127 mm) and be less than

0.001

inch (0.0243 mm) out-of-round. RDJC bore

should measure between 3.2495 inches (82.537 mm)

and 3.2505 inches (82.563 mm) and be less than

0.001

inch (0.0243 mm) out-of-round.

If necessary, rebore the cylinderto fit the next availa­ble oversize piston. Pistons and rings are available in

0.005

inch (0.127 mm),

0.010

inch (2.540 mm),

0.020 inch (0.508 mm) 0.030 inch (0.762 mm) and

0.040 inch (1.016 mm) oversize. If the cylinders do
not need refinishing, remove any existing ridges from

the top of the walls with a fine stone.

Pistons:

Clean thoroughly and inspect each piston. Clean the
carbon from the ring grooves and be sure all oil holes
are open. If any piston is badly scored or burred,
loose in the cylinder, has badly worn ring grooves or
otherwise is not in good condition, replace it. See
Figure

to match valve positions.

Check the clearances 90 degrees from the axis of the
piston pin and just below the oil control ring. Clear­ance should be

0.191 mm). If not, replace the piston and check the
cylinder for possible reconditioning.

55.

Ins fall pistons with valve relief recess
facing the camshaft side of engine

0.0055

inch to 0.0075 inch (0.140 to

CAST !RON

OIL CONTROL

INSTALL

VENTS

(AWAY

END

RINGS PISTON

OIL

CONTROL-^^^^^^^^^

'

'

FIGURE

AT

FROM

OF

VENTS

55.

PISTON

WITH

BOTTOM

CLOSED

PISTON)

-I

RINGS

RINGS

Inspect each ring carefully for fit in the piston

grooves and seating on thecylinderwall. Fit each ring

to the cylinder wall at the bottom of its travel, using a

piston to square the ring in the bore. Check the gap
with a feeler gauge. It should be
inch (0.25 to
butt ends of the rings.

0.51

mm). If the gap is too small, file the

Do

not use rings that need a lot
of filing. They will not seat right on the cylinder walls.
If oversize pistons are used, use the correct oversize
rings.

CONNECTING

RODS

Clean the connecting rods and check each for
defects. Check the connecting rod bushings for
proper clearance with the piston pin. Clearance
should be 0.0002 inch to 0.0007 inch

0.018 mm).
If the bushings are excessively worn, press them out

and install one new bushing from each side of the
bushing bore. Press the new bushingsonly until flush
with the sides

of

the rod to leave 1/16 inch to 7/64inch

(1.588 to 2.776lmm) oil groove in the center. See

Figure 56.

0.010

inch to 0.020

(0.0051

to

PISTON PINS CONNECTING ROD BEARINGS

Each piston pin should be a thumb push fit into its

pin

piston at room temperatures. If the

is excessively
loose, install a new one. If the condition is not cor­rected, install the next oversize pin. If the piston is
worn enough
replace

it.

so

that the oversize pin will not fit,

Inspect the connecting rod bearings for burrs,
breaks, pitts and wear. Measure the clearance between
bearings and the crankshaft journal. The clearance

should be 0.0010 inch to 0.0033 inch (0.025 to 0.084
mm). If necessary, replace with new standard or
oversize precision bearings.

54

CONNECTING

Redistribution or publication of this document, 

by any means, is strictly prohibited.

BUSHINGS

ROD

SIDES

TO PERMIT

GROOVE

ARROW

Rev.

ROD

CROSS-S

BUSHINGS

ECTl ON

)I

1;

\\

FIGURE

BE FLUSH WITH

OF

ROD

1/16"OIL

BEARING

MEASURE CLEARANCE IN

DIRECTION INDICATED BY

A881

56.

CONNECTING

ASSEMBLY AND INSTALLATION

1. Install connecting rods on each piston with pins
and retaining rings. If new bushings were in­stalled, check to see that ends are flush with
connecting rod to provide foroil recess in center.

2. Install all rings on each piston. All compression
rings will be marked

top

or identified in some
other manner. Place this mark toward closed end
of piston. Space ring gaps 1/4 of way around
piston from one another. No gap should be in line
with the piston pin.

3.

Position a bearing half in each connecting rod. Be
sure there is no dirt under bearing. This could
cause high spots and early bearing failure.

4. Oil cylinder walls. Install each piston in proper
,cylinder using a suitable installer. Each assembly

should be installed with stamp on piston facing
same direction as when removed.

5.

Position each connecting rod on crankshaft, oil
the journal, and install its rod cap with bearing

half. When installing rod cap, position

'

witness mark on forging matches mark on con-

necting rod. See Figure 57.

6.

Tighten cap screws to specjfied torque.

7.

Crank engine over by hand to see that all bearings

i

so

raised

are free.

8.

Install oil base with a new gasket.

9.

Install cylinder heads using proper bolt tighten-

ing sequence.

10.

Replace

oil.

CAMSHAFT

The camshaft is a one-piece machine casting, driven

through gears by the crankshaft. It rides on sleeve
bearings pressed into the crankcase.

In addition to providing a means of opening and
closing the valves, the camshaft operates the injec­tion pump and fuel transfer pump.

FIGURE

57.

CONNECTING ROD CAP

Removal:

1.

Remove rocker arms and push rods from valve

chambers.

2. Remove injection pump and fuel transfer pump
from engine.

3.

Remove crankshaft gear retaining washer by
removing lock ring on crankshaft.

4. Lay engine on its side to avoid dropping tappets
and remove camshaft assembly as a group.
necessary, pry

it

out with a screwdriver between

camshaft gear and crankcase.

5.

Remove valve tappets. These can be removed
only from the camshaft end of the push rod holes.

Repair:

smooth with

If

a lobe has become slightly scored, dress it

a

fine stone. If the camshaft is badly

worn orscored, replace it. After installing a new cam-

shaft, retime the injection pump to the engine. Never

install a new camshaft with old tappets.

Camshaft Gear.

This gear is a pressed fit on the

camshaft and drives it at 1/2 the crankshaft speed. To

remove the gear, use a hollow tool or pipe that will

inside the gear bore and overthe center pin. Press the
camshaft out of the gear bore. Be careful not to
damage the center pin.

Camshaft Bearings:

The camshaft bearings should

be replaced if the clearance to the camshaft is greater'

than specified, the bearings show cracks, breaks,

burrs, excessive wear, or other defects.

To

check the

rear bearing, remove the expansion plug at the rear of
the crankcase.

If

fit

.

?i5

PRESS

Redistribution or publication of this document, 

by any means, is strictly prohibited.

BEARING

FLUSH WITH

BOTTOM

RECESS

REAR

EARING

OF

BEAR

BEAR

I

I

NG

NG

PRESS

BEARING

PRESS

BEARING

FLUSH WITH

FLUSH WITH

FRONT CRANK-

FRONT CRANK­CASE SURFACE

CASE SURFACE

OIL

ALIGN

HOLES

FRONT

BEAR1 NG

FIGURE

59.

CAMSHAFT ENDPLAY

FIGURE

58.

CAMSHAFT BEARINGS

Press new bearings into place, Figure
rear bearing flush with the bottom of the expansion

plug recess. Press the front bearing in flush with the
crankcase front surface
aligned.
are a precision type. Afterthe rear bearing is installed,

insert a new expansion plug
sealing compound, and expand
sharp blows at its center.

Installation, Camshaft

1.

Install key and press camshaft gear on camshaft
until it bottoms on flange with no clearance.

2.

Install governor components.

3.

Slide thrust washer onto shaft. Measurecamshaft

end play; it should be

(0.178

4.

Lay engine on its side or end and insert push rod
tappets.

5.

Install camshaft assembly
marks

Figure

6.

Replace push rods and fuel transfer pump.

7.

When engine is reassembled, install injection

pump following the steps for lnjecfion

installation

step is critical.

58.

Press the

so

the oil passages are

Do

not attempt to ream the bearings as they

in

the recess, using

it

into place with

Assembly:

0.007

inch to

to

0.991

mm). See Figure

in

engine. Align timing

on

camshaft gear and crankshaft gear. See

60.

in the

FUEL

SYSTEM

0.039

59.

section. This

inch

Pump

WHEN INSTALLING

TIMING GEARS

-v-!

FIGURE

60.

TIMING

.

MARKS

CRANKSHAFT

Onan diesel engines use a counter-balanced, ductile

To

iron crankshaft.

increasetheshaftfatiguedurabili-

ty, all crankpin fillets are shot-peened during

manufacture. The four-cylinder model uses an ad-

ditional split-center main bearing.

56

CRANKSHAFT

Redistribution or publication of this document, 

by any means, is strictly prohibited.

A585

7

-

3/16"

(4.763

mrn)

II

FIGURE

61.

REMOVING CRANKSHAFT GEAR

Removal

Remove lock ring and retaining washer

1.

crankshaft gear.
Pull off crankshaft gear. It has two 1/4-20 UNC

2.
tapped holes for attaching a gear pulling ring.

in

front of

THIS AREATO

DURING

DURING

OPERATION

OPERATION

FIGURE

1.

Almen gauge reading 0.012-A (0.305).

62.

2. Peen with 0.019 inch (0.482 mm) diameter cast
steel shot.

3. Peen for 30 seconds on each crankpin fillet.

4. Mask off connecting rod bearing areas.

BE

SHOT- PEENINti

SHOT- PEENINti

SHOT-PEENING THE CRANKSHAFT

MASKED

Use care not to damage teeth if the gear is to be
reused. See Figure 61.

Remove oil pan, pistons and connecting rods.

3.

4.

Remove bearing cap from center main bearing.
Remove rear bearing plate from crankcase.

5.

Remove crankshaft through rear opening

6.
crankcase. Catch upper half of center main
bearing support as it slides off its mounting
surface.

Inspection:

Clean the crankshaft and blow out all oil

in

Undersize bearings and connecting rods are available

to rework the shaft to 0.010inch (0.254 mm),

inch

(0.508

mm), and 0.030 inch (0.762 mm) under-

0.020

size.

Main Bearings:

Replace main bearings if clearances
are greater than limits or if the bearings are worn,
grooved, or broken.

Precision replacement inserts and thrust washers are
available for all main bearings.

Do

not ream the.

bearings.

passages. Check journals for out-of-round, taper,
grooving or ridges. Pay particular attention to ridges
or grooveson eitherside of theoil holeareas. Unusual
conditions here often point to previous neglect of oil
changes.

If journal dimensions are not within limits, or the

journals are scored, regrind the crankshaft.

b

trained, experienced operator working with precision

Crankshaft Grinding:

Crankshaft grinding requires a

equipment. Procedures which may besatisfactoryfor
some spark-ignition engines may well be unsatisfac-

<

tory for diesel applications, resulting in expensive

Align the oil holes and press the new bearings into the
front and rear housings. Insert the center bearing

when the crankshaft is reinstalled.

Rear

Oil

Seal:

The rear oil seal is in the rear bearing
plate. If damaged, drive
plate. Using the oil seal installing tool (Onan

it

out from the inside of the

No.

420-0250), install a new seal with the rubber lip facing
outward (open side of seal inward). See Figure 63.

Drive the new seal flush with the rear surface of the
bearing plate. Leave the seal installer on during bear­ing plate installation to protect the oil seal.

'

failures. Onan emphasizes that if facilities or trained

personnel are not available, the crankshaft may be
sent to the factory.

Special procedures must be observed when rework­ing diesel crankshafts.

In

addition to machining, the

crankshaft must be shot-peened and super-finished.

I

Failure to

shot-peen

the crankpin fillets is likely to
cause early failure. When the shaft is machined,
follow this data and Figure 62 to shotpeen each crank
pin fillet.

Installation:

crankshaft to be sure

1.

Press front and rear main bearings into place,

After each installation step, check the

it

is not frozen into place.

align bearing and bearing housing oil holes.
not attempt to drive a bearing into a cold block or
rear bearing plate.

2. Install thrust washers and locking pins.

3. Oil bearing surfaces and install crankshaft from
rear

of

crankcase through rear bearing plate hole.

Do

57

8.

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Mount and secure rear bearing plate.

4.

5.

Heat timing gear on an electric burner or oven to

Install piston assemblies.

CRANKCASE

about 350" F (175°C). Install key on crankshaft, If the crankcase requires replacement, a new set of
then drivegear into place. Install retaining washer injection

and lock ring.

6.

Set upper half of center main housing on crank- injection pump must be retimed to the engine. If, on
shaft and rotate it into place. See Figure
Be sure it is installed with the side marked

.

64.

front

crankcase. These must be used and, in addition, the

the four cylinder models, the center main bearing

support requires replacement, the whole crankcase

pump

shims

will

be furnished with the

toward crankshaft gear. Set the two positioning must be replaced or returned to the factory to have a
dowels on the upper bearing mount. Install center new housing fitted.
main bearing cap and torque bolts to 97-102foot­pounds (131-138 Nom).

Check crankshaft end play.

7.

Use

enough rear Whenever new rings or pistons are installed or the
bearing plate shims and gaskets to provide
inch (0.254

mm)

to

0.015

inch (0.381

play. If gaskets of more than

mm)

0.015

0.010

end regular operation can be resumed. Run the engine for

inch

BREAK-IN PERIOD

cylinder refinished, the engine must be run-in before

15

to 20 minutes at no load, about 30 minutes at

(0.381 mm) total thickness are required, use a load, and 2 to 3 hours at 2/3 load. Regular operation
steel shim of proper thickness and a thin gasket can then be resumed. Avoid light load operation

on each side of shim. This avoids excessive during the following several hours for best ring
gasket compression and maintains bolt torque. seating to prevent oil consumption,

REAR BEARING PLATE

new

1/3

F

RONT

TALL FLUSH

"

THRUST WASHER

ALIGN OIL HOLES

IN BEARING CLIP FACING

DE SURFACE

FIGURE

CRANKSHAFT BROKEN LINE. ROTATE INTO

63.

MAIN BEARING INSTALLATION

SIDE MAR KED

TOWARD CRANKSHAFT

PLACE UPPER BEARING HOUSING

HALF IN POSITION INDICATED BY

''

POSITION

BEARING HALF CENTER MAIN BEARING

FIGURE

64.

CENTER MAIN BEARING HOUSING

58

HOUSING (UPPER HALF)

BE

SURE

TO

ALIGN OIL

Control

Redistribution or publication of this document, 

by any means, is strictly prohibited.

System

Due to the widevarietyof uses
are adapted, operating controls are not supplied,

the engines. In most cases, the engines are used for

prime power to operate other manufacturers equip­ment. Installation nearly always differs. Therefore,

F

the manufacturer or fabricator generally provides a
control for the complete unit.

to

which theseengi

r

ith

MAINTENANCE

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

PRE-HEAT SWITCH

SWITCH

I

L*

SI

NO.

12

WIRE

*

sz

in

the

FUEL SOLENOID

MANIFOLD

/

HEATER

BT

I

I

s2

+

111-

BI

-I

STARTER

FUEL SOLENOID

SWITCH

WIRING

I

I

DIAGRAM

"YPICAL

I

+CUSTOMER SUPPLIED

mANDARD

f

SCHEMATIC

ENGINE

99

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Redistribution or publication of this document, 

by any means, is strictly prohibited.

t'

Redistribution or publication of this document, 

by any means, is strictly prohibited.

Onan Corporation

1400

73rd Avenue N.E.
Minneapolis, MN 55432
1-800-888-ONAN

61 2-574-5000 International

Telex:

275477

Fax:

61

2-574-8087

Onan

is

a

registered trademark

Use

of

Onan

Corporation