Onan BGM Series User manual

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Printed in U.S.A.
Service Manual
0
BGM, NHM
965-0531
2-96

Safety Precautions
Thoroughly read the OPERATOR'S MANUAL before
operating the genset. Safe operation and top perfor-
mance can be obtained only with proper operation
and maintenance.
The following symbols in this Manual alert you to poten-
tial hazards to the operator, service person and equip-
ment.
M•M~®#!;I Alerts you to an immediate hazard
which will result in severe personal injury
or death.
IAWARNINGI Alerts you to a hazard or unsafe
practice which can resultin severepersonalinjury
or
death.
lA CAUTION I Alerts you to a hazard or unsafe
practice which can resultin personalinjury
or equip-
ment damage.
Electricity, fuel, exhaust, moving parts and batteries
present hazardswhich can result
in severe personal inju-
ry or death. GENERAL PRECAUTIONS
• Keep ABC fire extinguishers handy.
• Make sure all fasteners are secure and torqued
properly.
• Keepthe gensetand itscompartmentclean. Excess
oil and oily rags can catch fire. Dirt and gearstowed
in the compartment can restrict cooling air.
• Before working on the genset, disconnectthe nega-
tive
(-) battery cable at the battery to prevent start-
ing.
• Use caution when making adjustments while the
genset
is running-hot, moving or electrically live
parts can cause severe personal injury or death.
• Used engine oil has been identified by some state
and federal agencies as causing cancer or
reproductive toxicity. Do not ingest, inhale, or
contact used oil or its vapors.
• Benzene and lead
in some gasolines have been
identified by some state and federal agencies as
causing cancer or reproductive toxicity.
Do not to
ingest, inhale or contact gasoline or its vapors.
• Do not work
on the genset when mentally or physi-
cally fatigued or after consuming alcohol or drugs.
• Carefully follow all applicable local, state and
federal codes.
GENERATOR VOLTAGE IS DEADLY!
• Generator output connections must be made by a
qualified electrician
in accordance with applicable
codes.
• The genset must not be connected to the public util-
ity or any other source of electrical power. Connec-
tion could lead to electrocution of utility workers,
damageto equipment and fire.
An approved switch-
ing device must
be used to prevent interconnec-
tions.
• Use caution when working
on live electrical equip-
ment. Remove jewelry, make sure clothing and
shoes are dry and stand
on a dry wooden platform
on the ground or floor.
FUEL IS FLAMMABLE AND EXPLOSIVE
• Keep flames, cigarettes, sparks, pilot lights, electri-
cal arc-producing equipment and switches and all
other sources of ignition well away from areas
where fuel fumes are present and areas sharing
ventilation.
• Fuel lines must
be secured, free of leaks and sepa-
rated or shielded from electrical wiring.
• Use approved non-conductive flexible fuel hose for
fuel connections at the genset.
ENGINE EXHAUST IS DEADLY!
• Learn the symptoms of carbon monoxide poisoning
in this Manual.
• Never sleep
in the vehicle while the genset is run- ·~
ning unless the vehicle has a working carbon mon-
oxide detector.
• The exhaust system must
be installed in accor-
dance with the genset Installation Manual.
•
Do not use engine cooling air to heat the vehicle in-
terior.
• Make sure there
is ample fresh air when operating
the genset
in a confined area.
MOVING PARTS CAN CAUSE SEVERE PERSONAL
INJURY OR DEATH
• Do not wear loose clothing or jewelry near moving
parts such as PTO shafts, fans, belts and pulleys.
• Keep hands away from moving parts.
• Keep guards
in place over fans, belts, pulleys, etc.
BATTERY GAS IS EXPLOSIVE
• WEAR SAFETY GLASSES and DO NOT SMOKE
while servicing batteries.
• When disconnecting or reconnecting battery
cables, always disconnect the negative
(-) battery
cable first and reconnect it last to reduce arcing.
MBL-1

Table of Contents
SECTION TITLE PAGE
SAFETY PRECAUTIONS Inside Front Cover
1 INTRODUCTION .................................................. 1-1
2 GENERAL SPECIFICATIONS ...................................... 2-1
3 DIMENSIONS AND CLEARANCES ................................. 3-1
4 TORQUE SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . .. . . 4-1
5 PREPARING FOR SERVICE ....................................... 5-1
Troubleshooting ................................................. 5-1
Safety .......................................................... 5-1
Special Tools .................................................... 5-2
Removing the Genset
............................................ 5-2
6 ENGINE -PRIMARY SYSTEMS .................................... 6-1
Troubleshooting Engine Primary Systems ........................... 6-2
Exhaust System
................................................. 6-6
Cooling System ................................................. 6-7
Ignition System
................................................. 6-1 0
Cylinder Compression Test
...................................... 6-13
Crankcase Breather Assembly
................................... 6-13
Governor and Carburetor Adjustments ............................ 6-14
Fuel System
................................................... 6-19
Electric Starter ................................................. 6-35
7. CONTROL ....................................................... 7-1
Introduction . . . . .. . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . 7-1
Control Description {Mechanical-governor generator sets) ............ 7-2
Control Operation
............................................... 7-3
Control Description {Electronic-governor generator sets)
.............. 7-8
Control Operation
.............................................. 7-1 0
Control Troubleshooting
......................................... 7-15
A. WARNING: A.
The engine exhaust from this product
contains chemicals known to the State
of California to cause cancer, birth
defects or other reproductive harm.

SECTION TITLE PAGE
8. GENERATOR ..................................................... 8-1
Generator/Control Component Descriptions ......................... 8-1
Generator Operation ............................................. 8-2
Generator Troubleshooting
....................................... 8-5
Generator/Ignition Component Service
............................. 8-8
Brushes and Slip Rings
.......................................... 8-13
Generator Testing
.............................................. 8-15
9 ENGINE BLOCK ASSEMBLY
...................................... 9-1
General . . . . . . . . . .. . . . .. .. . . . . . . . . . . . .. . . .. .. . . . . . . . . . . . . . . . . . . . 9-1
Oil Filter and Adapter . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1
Cylinder Heads .................................................. 9-1
Valve System ................................................... 9-4
Gear Cover
..................................................... 9-9
Governor Cup (Mechanical} ...................................... 9-1 0
Timing Gears and Camshaft
..................................... 9-1 0
Lubrication System . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .. .
9-11
Piston Assembly ................................................ 9-13
Crankshaft
..................................................... 9-1 7
Cylinder Block
....... · ........................................... 9-18
Bearings
...................................................... 9-21
Oil Seals ...................................................... 9-22
10 SERVICE CHECKLIST
............................................ 1 0-1
Mounting ...................................................... 1 0-1
Lubrication ..................................................... 1 0-1
Wiring ......................................................... 1 0-1
Initial Start and Adjustments ..................................... 1 0-1
Output Check .................................................. 1 0-1
Exhaust System ................................................ 1 0-1
Fuel System ................................................... 1 0-1
Control ........................................................ 10-2
Mechanical
.................................................... 10-2
11 WIRING DIAGRAMS ............................................ 11-1
Appendix A TROUBLESHOOTING CHARTS . . . . . . .. . . . . .. . . . . .. . .. . . . . . . . . . .. . A-1
ii

Section 1. Introduction
This is the service manual for the Series BGM and
NHM generator sets (gensets). Read and carefully
observe all
of the instructions and precautions in
this manual.
IAWARNINGllmproper service or parts replace-
ment can lead to severe personal injury or death
and to damage to equipment and property. Ser-
vice
personnel must be qualified to perform
electrical and mechanicalservice.
IAWARNINGI Unauthorized modifications or re-
placement of fuel, exhaust, air intake or speed
control system components that affect engine
emissions are prohibited by law in the State of
California.
IAWARNINGI LPG (liquified petroleum gas) is
flammable and explosive and can cause as-
phyxiation. NFPA 58, Section 1.6 requires
all
persons handling LPG to be trained in proper
handling and operating procedures.
See the Operator's Manual for instructions con-
cerning operation, maintenance and storage and
for recommendations concerning engine lubricat-
ing oil and fuel.
See the Installation Manual for important recom-
mendationsconcerning the installation andfora list
of the installation codes and standards for safety
which
may be applicable.
See the Parts Manual for parts identification num-
bersand requiredquantitiesandforexploded
views
of the genset subassemblies. Genuine Onan® re-
placement parts are recommended forbestresults.
When contacting Onan forparts, service or product
information, be ready
to provide the model number
and the serial number, both ofwhich appear on the
genset nameplate. See Table 1-1 for the signifi-
cance of each character
of the model number and
Figure
1-1 for how the model and serial numbers
are displayed on the nameplate.
1-1
TABLE 1-1. MODEL NUMBER
z
I
1
NHM
I
2
E
I
3
1. Rated Power in Kilowatts
2. Genset Family
3. Starting Method Code
A
I
4
4. Voltage and Frequency Code
26105
I
5
5. Options and Special Features Code
6. Spec Letter designating modifications
NAMEPLATE WITH TYPICAL MODELAND
SERIAL NUMBER DATA
IMPORTANT ENGINE INFORMATION
E
I
6
~
ONAN CORPORATION
1400 73rd Ave. NE
Minneapolis, MN 55432
Model No.: 7NHM-FA/26105F Made in U.S.A.
SIN: A953123456
ACVoHs: Ph: kW:
Amps:
PI:
RPM:
Fuel: Hz:
Bat:
12V
Insulation -NEMA Class Ambient: 400 C INI3461 URC
REFER TO OPERATOR'S MANUAL FOR MAINTENANCE
SPECIFICATIONS AND ADJUSTMENTS.
THIS ENGINE MEETS 1995-1998 CALIFORNIA
EMISSIONS REGULATIONS FOR ULGE ENGINES. EM
SN5980U1G2RA 980cc
FIGURE 1-1. TYPICAL NAMEPLATE

Section 2. General Specifications
GASOLINE MODELS
BGM NHM
GENERATOR: 4-Pole Revolving Field, Self-Excited, Electronically Regulated, 1-Phase
Power (watts) 5000 6800
Frequency (Hertz) 60 60
Voltage 120 120
Current (amperes) 41.7 56.7
Speed (RPM) 1800 1800
FUEL CONSUMPTION:
No load gph
(1/h)
0.3 (1.3) 0.4 {1.5)
Half load gph
(1/h)
0.5 (1.9) 0.7 (2.6)
Full load gph
(1/h)
0.9 (3.4) 1.3 (4.9)
ENGINE: 2-Cylinder Opposed, 4-Cycle, Spark-Ignited, Side-Valve, Air Cooled
Bore 3.250 inch (83 mm) 3.563 inch (90 mm}
Stroke 2.875 inch (73 mm) 3.000 inch (76 mm)
Displacement 48 inch3 (782 cc) 60 inch3 (980 cc}
Compression Ratio
7.0: 1 7.0: 1
Minimum Cylinder Compression 75 psi (517 kPa) 75 psi (517 kPa)
Test Pressure
Oil Capacity (with filter)* 3.5 quart (3.3
I) 3.5 quart (3.3 I)
Intake Valve Clearance (Cold) 0.005 inch (0.13 mm) 0.005 inch (0.13 mm)
Exhaust Valve Clearance (Cold) 0.013 inch (0.33 mm) 0.013 inch (0.33 mm)
Spark Plug Gap 0.025 inch (0.64 mm) 0.025 inch (0.64 mm)
Spark Plug Tightening Torque 8 !bs-ft
(1 0 N-m) 8 lbs-ft
(1 0 N-m)
Ignition Timing (Begin Spec
F)
12° BTDC non-adjustable 12° BTDC non-adjustable
Ignition Timing (Prior to Spec
F)
14°-18° BTDC non-adjustable 14°-18° BTDC non-adjustable
Maximum Fuel Supply Pressure 6 psi
(41 kPa) 6 psi
(41 kPa)
at Carburetor
Maximum Fuel Pump
lift 3 feet (0.9 m) 3 feet (0.9 m)
Fuel Fitting 5/16 inch OD Hose Barb 5/16 inch OD Hose Barb
Exhaust Tailpipe Requirements 1-3/8 inch
ID 18 Ga Steel Tubing 1-3/8 inch ID 18 Ga Steel Tubing
CONTROL AND CRANKING SYSTEM: 12 VDC
Nominal Battery Voltage 12 volts
Minimum Battery Cold Cranking 360/450 amperes
Capacity: Above/Below Freezing
Fuse
F1 (Control Board, Spec A only) 5 amperes slow-blow
Fuse
F2 (Fuel, Spec A only) 5 amperes slow-blow
Fuse
F1 (Control Board, Begin Spec B) 10 amperes
Fuse
F2 (Choke/Fuel, Begin Spec D) 10 amperes mini-bayonet
*
-See Periodic Maintenance for oil filling instructions.
-----~~ ---

LPG MODELS
NHM
GENERATOR: 4-Pole Revolving Field, Self-Excited, Electronically Regulated, 1-Phase
Power (watts) 6500
Frequency (Hertz) 60
Voltage 120
Current (amperes) 54.2
Speed (RPM) 1800
FUEL CONSUMPTION:
No load lbs/h (kg/h) 2.2 (1.0}
Half load lbs/h (kg/h) 3.6 (1.7}
Full load lbs/h (kg/h) 6.2 (2.8}
ENGINE: 2-Cylinder Opposed, 4-Cycle, Spark-Ignited, Side-Valve, Air Cooled
Bore 3.563 inch (90 mm)
Stroke
Displacement
Compression Ratio
Minimum Cylinder Compression
Test Pressure
Oil Capacity (with filter)*
Intake Valve Clearance (Cold}
Exhaust Valve Clearance (Cold)
Spark Plug Gap
Spark Plug Tightening Torque
Ignition Timing (Begin Spec F)
Ignition Timing (Prior to Spec F)
LPG Vapor Supply Pressure Range
(Vapor-Withdrawal Only)
LPG Connection for Vapor Withdrawal
LPG Connection for Liquid Withdrawal
Exhaust Tailpipe Requirements
CONTROL AND CRANKING SYSTEM: 12 VDC
!---------"'
Nominal Battery Voltage
3.000 inch (76 mm)
60 inch3 (980 cc)
7.0: 1
75 psi (517 kPa)
3.5 quart (3.3
I)
0.005 inch (0.13 mm)
0.013 inch (0.33 mm)
0.025 inch (0.64 mm)
8 lbs-ft
{1 0 N-m)
12° BTDC non-adjustable
14
o-18° BTDC non-adjustable
9 to 13 inch (229 to 330 mm) W. C. (water column)
3/4 inch
NPT Tapping
1/4 inch
NPTF Tapping
1-3/8 inch iD 18
Ga Steel Tubing
12 volts
Minimum Battery Cold Cranking I 3601450 amperes
Capacity: Above/Below Freezing
~--- tl -------------~-~--,~- ~-----------;
Fuse F1 (Control Board) 10 amperes
~die Mainte;;;~;~-roroil filling ~~.struction""'~s=. =""'-"""" =""'=""-~===--·

Section 3. Dimensions and Clearances
MODELS
BGM NHM
CYLINDERS AND All clearances listed at 70° F
(21 o C) room temperature.
PISTON ASSEMBLY Values are in inches (millimeters) unless specified
otherwise. Dimensions apply to Specs A, B and C
gensets except as indicated.
Cylinder Bore 3.2490-3.2500 3.5625-3.5635
(Std size honed) (82.525-82.550 mm) (90.488-90.513 mm}
Cylinder Taper 0.005 0.005
(Max} (0.13 mm) (0.13 mm)
Cylinder Out
Of 0.003 0.003
Round (Max) (0.076 mm) (0.076 mm)
Clearance In 0.0044-0.0066 0.0070-0.0090
Cylinder (0.112-0.168 mm) {0.178-0.229 mm)
Ring Gap (top and 0.008-0.018 0.009-0.019
second rings) {0.20-0.46 mm) (0.23-0.48 mm)
Piston Ring
#1 (top) Spec A, B sets: 0.080-0.081 0.080-0.081
Groove Width (2.03-2.06 mm) (2.03-2.06 mm)
Spec C sets: 0.0602-0.0612 0.0602-0.0612
(1 .53-1.55 mm) (1.53-1.55 mm)
Piston Ring
#2
Spec A, B sets: 0.080-0.081 0.080-0.081
Groove Width (2.03-2.06 mm) (2.03-2.06 mm)
Spec C sets: 0.0602-0.0612 0.0602-0.0612
(1.53-1 .55 mm) (1.53-1.55 mm)
Piston Ring
#3
Spec A, B sets: 0.188-0.189 0.188-0.189
Groove Width (4.78-4.80 mm) (4.78-4.80 mm)
Spec C sets: 0.1193-0.1203 0.1193-0.1203
(3.03-3.06 mm) (3.03-3.06 mm)
Piston Pin 0.6875-0.6877 0.7500-0.7502
Diameter (17.46-17.47 mm) (19.05-19.06 mm)
Piston Pin Clearance 0.0002-0.0007 0.00005-0.00055
In Rod (0.005-0.018 mm) (0.001-0.014 mm)
Connecting Rod 0.0020-0.032 0.0020-0.0160
Side Clearance (0.051-0.813 mm) (0.051-0.406 mm)
Connecting Rod 0.0020-0.0033 0.0005-0.0028
Bearing Clearance (0.051-0.084 mm) (0.013-0.071 mm)
--
3-1

-------- ---------'--------
--------- ---- --------
MODELS BGM NHM
CRANKSHAFTAND
CAMSHAFT
Crankshaft Main Bearing 1.9992-2.0000 1.9992-2.0000
Journal Diameter (50.780-50.800 mm) (50.780-50.800 mm)
Crankshaft Rod Journal 1.6252-1.6260 1.6252-1 .6260
Bearing Diameter (41.280-41.300 mm} (41.280-41.300 mm)
Crankshaft Main 2.0024-2.0034 2.0024-2.0034
Bearing Diameter (50.860-50.886 mm) (50.860-50.886 mm)
Crankshaft Main 0.0024-0.0042 0.0025-0.0038
Bearing Clearance (0.064-0.107 mm) (0.064-0.097 mm)
Crankshaft End 0.006-0.012 0.005-0.009
Play (0.15-0.30 mm) (0.13-0.23 mm)
Camshaft Journal 1.3740-1.3745 1.3740-1.3745
Diameter (34.900-34.912 mm) (34.900-34.912 mm)
Camshaft Bearing 1.376-1.377 1.376-1.377
Diameter (34.950-34.976 mm) (34.950-34.976 mm)
Camshaft Bearing 0.0015-0.0030 0.0015-0.0030
Clearance (0.038-0.076 mm) (0.038-0.076 mm)
Camshaft End Play 0.011 0-0.0480 .0.0030-0.0120
(0.280-1.22 mm) (0.076-0.305 mm)
VALVE AND LIFTERS
Valve Spring Free 1.600 1.6620
Length {approx.) (40.640 mm) (42.214 mm)
Valve Spring Compressed 1.3750 1.3750
Length (Valve Closed) (34.925 mm) {34.925 mm)
Valve Spring Tension 71-79 lbs 71-791bs
I Open (9.8-1 0.9 N} (9.8-10.9 N)
Valve Spring Tension 38-421bs 38-421bs
Closed (5.3-5.8 N) (5.3-5.8 N)
3-2

MODELS BGM NHM
Valve Face Angle 440 44°
Valve Seat Angle
45°
45°
Valve Stem 0.2795-0.2800 0.3425-0.3430
Diameter (Intake) (7.0993-7.1120 mm) (8.700-8.712 mm)
Valve Stem 0.2780-0.2785 0.341 0-0.3415
Diameter (Exhaust) (7.0612-7.0739 mm) (8.661-8.674 mm)
Valve Guide Intake Exhaust Intake and Exhaust
Inside Diameter 0.2810-0.2820 0.2805-0.2815 0.344-0.346
(7.1374-7.0739 mm) (7.1200-7.1501 mm (8.738-8.788 mm)
Valve Stem 0.001 0-0.0025 0.0010-0.0025
Clearance (Intake) (0.025-0.064 mm) (0.025-Q.064 mm)
Valve Stem 0.0020-0.0035 0.0025-0.0050
Clearance (Exhaust) (0.0508-0.0889 mm) (0.064-0.127 mm)
Valve Lifter 0.7475-0.7480 0.7475-0.7480
Diameter (18.987-18.999 mm) (18.987-18.999 mm)
Valve Lifter Bore 0.7500-0.7515 0.7500-0.7515
Diameter (19.050-19.088 mm) (19.050-19.088 mm}
Valve Lifter To 0.0020-0.0040 0.0020-0.0040
Block Clearance (0.0508-0.1016 mm) (0.0508-0.1 016 mm)
Valve Seat 1.4425-1.4435 1.5690-1.5700
Diameter (Intake) (36.6395-36.6649 mm) (39.738-39.764 mm)
Valve Seat 1.192-1.193 1.2550-1.2560
Diameter (Exhaust) (30.28-30.30 mm) (31.877-31.902 mm)
Valve Seat Bore 1.4395-1.4405 1.5645-1.5655
Diameter (Intake) (36.563-36.589 mm) (39.738-39.764 mm)
Valve Seat Bore 1.189-1 .190 1.2510-1.2520
Diameter {Exhaust) 30.20-30.23 mm) (31.775-31.801 mm)

Section 4. Torque Specifications
MODEL BGM
TORQUE Use engine oil as a lubricant for all threads
SPECIFICATIONS EXCEPT the spark plug and rotor through-bolt threads
FOOT-POUNDS NEWTON-METERS
Cylinder Head Bolts (cold) 14'-16 19-22
ConnectinQ Rod Bolts 12-14 16-19
Rear Bearing Plate 25-27 34-37
Flywheel MountinQ Screw 50-55 68-75
Oil Base 20-24 27-33
Gearcase Cover 10-12 14-16
Spark Pluo 7-9 9-12
Exhaust Manifold
9-11 12-15
Intake Manifold 6-10 8-14
Rotor Throuah-Bolt 45-55 61-75
Starter Mountino Screws 30-33 41-45
Stator Clamp Screws 10-12 11-16
Adapter to Engine 25-27 34-37
Mounting Screws
Adapter to Generator 25 34
Mounting Screws
Rear Vibration Isolator
Center Screw 30-33 41-45
Flange to Drip Tray Screws 10-12 14-16
Front Vibration Isolator
Flange to Oil Base Screws 19-22 26-30
Center Screw 28-32 38-43
Vibration Isolators
Center Screw 30-33 ft-lbs 41-45
Flange to Drip Tray Screws 10-12 ft-lbs 14-16
Voltage Regulator
Mounting Bracket Screws 7-8 ft-lbs
9-11
Regulator Attachment Screws 5-6 ft-lbs 7-8
Start Solenoid Attachment Screws 5-6 ft-lbs 7-8

MODEL NHM
TORQUE Use engine oil as a lubricant for all threads
SPECIFICATIONS EXCEPT the spark plug and rotor through-bolt threads.
FOOT-POUNDS NEWTON-METERS
Cylinder Head Nuts (cold} 14 19
(with
com_oression washers\
Cylinder Head Nuts (cold) 17 23
(without comoression washers)
Connectina Rod 27-29 37-39
Rear
Bearing_ Plate 25-28 34-38
Flywheel MountinQ Screw 50-55 68-75
Starting Mounting Bracket to 20-24 27-33
Oil Base Screws
Gearcase Cover 10-12 14-16
Spark
PluQ
7-9 9-12
Exhaust Manifold 20-23 27-31
Intake Manifold 14-16 19-22
Rotor
Throu_g_h-Bolt
45-55 61-75
Starter Mounting Screws 30-33 41-45
Stator Clarno Screws 10-12 14-16
Adapter
to Engine 25-27 34-37
Mounting Screws
Adapter to Generator 25 34
MountinQ Screws
Rear Vibration Isolator
Center Screw 30-33 41-45
Flanae to Drip Tray Screws 10-12 14-16
Front Vibration Isolator
Flange to Oil Base Screws 19-22 26-30
Center Screw 28-32 38-43
Vibration Isolators
Center Screw 30-33 ft-lbs 41-45
Flange to Drip Tray Screws 10-12 ft-lbs 14-16
Voltage Regulator
Mounting Bracket Screws 7-8 ft-lbs
9-11
Regulator Attachment Screws 5-6 ft-lbs 7-8
Start Solenoid Attachment Screws 5-6 ft-lbs 7-8

Section 5. Preparing for Service
TROUBLESHOOTING
See Troubleshooting to determine the probable
cause of the problem before removing the genset
for service.
SAFETY
There are hazards in servicing gensets. Study
Safety Precautions and become familiar with the
hazards listed in Table
5-1 .Note the following safe-
guards and ways of avoiding hazards:
• Use personal protection: Wear appropriate
protective safety equipment, such as:
Safety shoes
Gloves
Safety glasses
Hard hats
Do not wear rings or jewelry and do not wear
loose clothing that might get caught
in equip-
ment.
• Reducethe hazard:A safe, orderly workshop
area and well-maintained equipment reduce
the hazard potential. Keep guards and shields
in place on machineryand maintain equipment
in good working condition. Storeflammable liq-
uids
in approved containers; away from fire,
flame, spark, pilot light, switches, arc-produc-
ing equipment and other ignition sources.
Keep the workshop clean and well-lighted and
provide adequate ventilation.
• Develop safe work habits: Unsafe actions
cause accidents with tools and machines. Be
familiar with the equipment and know how to
useit safely. Usethe correcttool forthejoband
checkitscondition beforestarting. Complywith
the warnings in this manual and take special
precautions when working around electrical
equipment. Do not work alone if possible and
take no risks.
• Be prepared for an accident:Keep fire extin-
guishers and safety equipment nearby. Agen-
cies such as the Red Cross and public safety
departmentsoffercourses
in firstaid, CPRand
fire control. Take advantage ofthis information
to be ready to respond to an accident. Learn to
be safety-conscious and make safety proce-
dures part of the work routine.
TABLE 5-1. HAZARDS AND THEIR SOURCES
• Leaking or spilled fuel
Fire and • Hydrogen gas from battery
Explosion
• Oily rags improperly stored
• Flammable liquids improperly
stored
• Hot exhaust pipes
Burns
• Hotengine and generatorsur-
faces
• Electrical shorts
Poisonous • Operating genset where ex-
Gas haust gases can accumulate
• Improper generator connec-
tions
Electrical • Faulty wiring
Shock (AC) • Working in damp conditions
• Jewelry touching electrical
components
Rotating • Fan guards not in place
Machinery
Slippery
• Leaking or spilled oil
Surfaces
Heavy • Removing gensetfrom vehicle
Objects
• Removing heavy components

SPECIAL TOOLS
The tools listed below are necessary for servicing
the genset. See the Onan Tool Catalog.
Engine Tools
Torque wrench: 0-75 lbs-ft (0-1 00 N-m)
Hole gauge: 0.300-0.400 inch (5-1 0 mm)
Outside micrometer set: 0-4 inch (0-1
00 mm)
Telescoping gauge set: up
to 4 inch (1 00 mm)
Feeler gauge
Plasti-Gage bearing clearance guide
Spark plug gap gauge
Oil pressure gauge: 0-30 psi (0-200 kPa)
Fuel pressure gauge (for gasoline): 0-10 psi
(0-75 kPa)
Manometer (for LPG):
14 inch (350 mm) WC
Inclined Manometer (for LPG): 1 inch (25 mm)
we range with 0.01 inch (0.2 mm) we di-
visions
Cylinder compression tester
Flywheel puller
Crankshaft gear puller ring, bolts and puller
(or special shoulder bolts and flywheel
puller)
Snap ring pliers
Combination main and
cam bearing remover
Combination main and
cam bearing driver
Oil seal loader and driver
Cylinder ridge reamer
Piston ring spreader
Piston groove cleaner
Piston ring compressor
Cylinder hone
Valve spring compressor
Valve lock replacer
5-2
Valve seat cutter kit
Valve guide driver
Slide
hammer
Lead or dead-blow hammer
Generator and Control Tools
Rotor removal tool (headless bolt)
Battery hydrometer
Frequency meter
Digital multi-meter:
AC and DC Voltage, Ohms
and Diode Check
Loadtestpanelandleads
Voltage Regulator Testor and Adaptor (1-Ph)
Rotor and Stator Testor and Adaptor
REMOVING THE GENSET
Some service procedures will require that the gen-
setbe removed from
the vehicle. The gensetisnor-
mallymounted in a special compartmenton
the ve-
hiclefloor. Because installationsvary, itis notpossi-
ble
to describe a specific removal procedure. Con-
tact
the vehicle manufacturer or installer ifthe best
way to remove the genset is not obvious.
Disconnections at the Genset
1. First disconnect the negative (-) battery cable
from the batteryand then disconnect the bat-
tery cables from the genset.
IAWARNINGI Sparks and high current could
cause fire and other damage to the battery,
batterycables
and vehicle if the looseends
of cables connected to the battery touch.
Always disconnect the negative (-) battery
cable from the battery before disconnect-
ing the batterycables from the genset.
2. Disconnect the remote control wiring harness
connector at the genset.
3. Disconnect the generator output wiring and
conduit from the povver distribution panel
or
box on the all wires to make re-
connections easier.

4. Disconnectthe exhaust tailpipe from the outlet
of the muffler. See EXHAUST SYSTEM under
Section
6. Engine-Primary Systems.
5. Disconnect the fuel supply line from the gen-
set. Followthe applicable instructions depend-
ing on the fuel.
IA WARNING IGasoline and LPG (liquified pe-
troleum gas) are flammable and explosive
and can cause severe personal injury or
death. Do not smoke if you smell gas or gas-
oline or are near fuel tanks or fuel-burning
equipment
or are in an area sharing ventila-
tion with such equipment. Keep flames,
sparks,
pilot lights, electrical arcs and arc-
producing equipment and all other sources
of ignition well away.
Gasoline Fueled Gensets: Disconnect the
fuel line from the genset and securely plug the
end ofthe fuel line
to prevent leakageoran ac-
cumulation of explosive gasoline vapor.
LPG Fueled Gensets: Close the fuel shutoff
valve(s) atthe LPG container(s) and move the
vehicle outside and away from below-grade
spaces where LPG could accumulate.
To
purge the fuel line and genset as much as pos-
sible, run the genset (if it starts) until it runs out
of fuel with the LPG valve(s) closed. Also see
the specificadditional instructions which follow
for purging liquid-withdrawal and vapor-with-
drawal systems and for capping off the gas
supply line.
IAWARNINGI LPG is flammable and explo-
sive and can causeasphyxiation. NFPA 58,
Section 1.6 requires
all persons handling
LPG to be trained in proper handling and
operatingprocedures.
LPG
"sinks" when it escapes into the air
and can accumulate in explosive con-
5-3
centrations. Before disconnecting the LPG
fuel line,
close the fuel shutoff valve(s) at
the LPG container(s) and move the vehicle
outside and away from pits or basements or
other below-grade spaces where LPG
could accumulate.
PurgingLPGLiquid-WithdrawalSystems (See
Figure 6-25 On Page 6-29): Purge the supply
line further by loosening the threaded supply
connection at the LPG filter on the genset just
enough to hear gas escaping. Unthread the
connector when no more gas is heard escap-
ing.
To purgethe LPG trapped between the so-
lenoid and regulator, loosen the flexible hose
connector at the fuel solenoid just enough to
hear gas escaping, and then retighten. Finally,
capthe end ofthefuel supply hose orpipe with
a 1/4 inch NPTF pipe cap to prevent fuel from
escaping
if someone inadvertently opens the
shutoff valve(s) at the LPG container(s).
IOAWARNINGI Large volumes of LPG can be
released in the process of disconnecting a
liquid-withdrawal type
of LPG supply sys-
tem. Before disconnecting LPG fuel con-
nections, make sure the the fuel shutoff
valve(s) at the LPG container(s) are closed
and that the vehicle is outside and away
from pits or basements or other below-
grade spaces where LPG could accumu-
late.
Purging LPG Vapor-Withdrawal Systems (See
Figure 6-29 On Page 6-32): Disconnect the
gas supply hose at the carburetor and the fuel
solenoid shutoff valve leads at the control box
on the genset. If the pressure regulator/sole-
noid valveassembly isalsotobe removed, cap
the end of the fuel supply line with a threaded
pipe cap to preventfuel from escaping
if some-
one inadvertently opens the shutoff valve(s).

Removal of the Genset from the Vehicle
See Figure 5-1. When the genset has been discon-
nected from the electrical, exhaust and fuel sys-
tems, examine its mounting boltsand supportmem-
bers. The genset drip tray is normally bolted to the
vehicle framework. Make sure that the genset
is
firmly supported before loosening any mounting
bolts or support members. A fork lift is recom-
mended to lift or move the genset.
IJiwARNINGI Gensets are heavy and can cause
severe
personal injury if dropped. Use a forklift
or other suitable means to handle the genset
while removing or installing it. Keep hands and
feet clearincase the genset is dropped.
FIGURE 5-1. SET REMOVAL
5-4

Section 6. Engine -Primary Systems
The engine primary systems and service proce-
durescovered
in thissection do notrequire removal
of the cylinder heads, gearcase or rear bearing
plateforaccess. Itmaybe possibletoperform some
of these procedures without removing the genset
from the vehicle.
TROUBLESHOOTING ENGINE PRIMARY
SYSTEMS
Regular maintenance can prevent many of the
problems listed below. Removing and cleaning the
refer to Periodic Maintenance in the Operator's
Manual for instructions
on howtoclean the cylinder
heads using Onan "4C".
The following troubleshooting tables are designed
to help you thinkthrough genset problems.
To save
time troubleshooting, read the entire manual ahead
of time to understand the genset. Try to think
through problems. Go over what was done during
the lastservicecall. Theproblemcould be as simple
as an empty fuel tank, closed fuel shutoff valve,
loose wire, blown fuse or tripped circuit breaker.
cylinder heads every500 hours is especially impor- See Section
7. ControlSystemand Section B. Gen-
tant for gasoline models. Before considering major erator for control and generator troubleshooting
engine service because of abnormal performance, tables.
IA WARNING I Many troubleshooting procedures present hazardswhich can result in severe personal
injury or death. Only qualified service personnel with knowledge of fuel, electricity, and machinery
hazards should perform serviceprocedures. Review safety precautions on inside cover page.
Trouble Possible Cause Corrective
Action
Engine
Misfires
Engine
Backfires
1. Faulty ignition due to:
a. worn or fouled spark plugs.
b. faulty ignition coil.
c. faulty plug wires.
2. Lean fuel mixture due to:
a. incorrectly adjusted
fuel mixture screws.1
b. incorrect float level.1· 2
c. dirt in carburetor.
d. vacuum leak.
e. altitude setting.
3. Contaminated fuel.2
4. Carburetor icing.2
1. Faulty ignition due to
incorrect spark plug gap.
2. Lean fuel mixture due to:
a. incorrectly adjusted fuel
adjustment screws.1
b. incorrect float level.1·2
c. dirt in carburetor.
3. Mechanical damage to engine.
1 - Prior to Spec F only
2 - Gasoline models only
1a. Replace spark plugs.
1
b. Test coil and replace if necessary.
1c. Test spark plug wires and replace
if faulty.
2a. Adjust carburetor main
and idle adjustment screws.1
2b. Adjust carburetor float level.1
2c. Disassemble carburetor and clean all
internal passages.1 Replace fuel filter.
2d. Locate leak and correct as required.
2e. Reset altitude adjust knob on carburetor.
3. Drain fuel tank and refill with fresh fuel.
4. Place air preheater
in winter position.
1. Reset spark plug gap.
2a. Adjust carburetor main and idle
mixture screws.1
2b. Adjust carburetor float level.1
2c. Disassemble carburetor and clean
all internal passages.1
3. See Engine Block Assembly section.

TROUBLESHOOTING ENGINE PRIMARY SYSTEMS
lA WARNING IManytroubleshootingprocedurespresenthazardswhichcan result inseverepersonal
injury or death. Only qualified servicepersonnel with knowledge of fuel, electricity, and machinery
hazards should perform service procedures. Reviewsafetyprecautions on inside cover page.
Trouble
Engine
Lacks
Power
Possible Cause
1. Faulty ignition due to incorrect
spark plug gap.
2. Dirty air cleaner.
3. Restricted fuel flow due to:
a. Plugged fuel filter.
b. Faulty fuel pump.
4. Incorrect fuel mixture due to:
a. incorrectly adjusted fuel
mixture screws.1
b. incorrect float level.1, 2
c. dirt in carburetor.
d. vacuum leak.
e. altitude setting.
5. Exhaust system blocked or
restricted.
6. Incorrect valve tappet clearance.
7. Excessive engine wear or
damage to engine.
8. Carburetor air preheater set
incorrectly.
2
9. Combustion chamber deposits.
Corrective Action
1. Reset spark plug gap.
2. Replace air cleaner.
3a. Replace fuel filter.
3b. Test fuel pump and repair or replace
if faulty.
4a. Adjust carburetor main and idle
adjustment screws.1
4b. Adjust carburetor float level.1
4c. Disassemble carburetor and clean all
internal passages.1 Replace fuel filter.
4d. Repair vacuum leak.
4e. Reset altitude adjust knob on carburetor.
5. Locate and remove cause of blockage.
6. Adjust valve tappets (see Engine Block
Assemblysection).
7. See Engine BlockAssemblysection.
8. In hot weather, place air preheater in
summer position.
9. Clean combustion chamber.
10.(Spec A sets) No-ioad speed 10. Adjust (mechanical) governor.
set too low: excessive
governor droop.
11.Contaminants
in LPG regulator. 1 11. Clean LPG regulator.
(liquid-withdrawal systems}
1 - Priorto Spec F only
2 - Gasoline models only
6-2