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General Motors 8.1L Engine

The General Motors 8.1L is a 8.1 L 8-cylinder natural aspiration engine rated at 1500 rpm, producing up to 121 kW. It powers generator sets from Cummins/Onan, General Motors, Kohler, SDMO and Taylor Power, including the GGLB-5791965, 8.1L Powertrain, 100REZG and 125RZG. It holds 10 L (2.6 gal) of oil and 10 L (2.6 gal) of coolant.

Also known as: 8.1L, GM 8.1L

Part of the General Motors 8.1L engine family — 3 variants share parts & fitment.

8.1 L

Displacement

Cylinders

1500 rpm

Rated speed

121 kW

Gross power

On this pageSpecs Generator sets Maintenance FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	10.0 L
Coolant capacity	10.0 L
Displacement	8.1 L
Cylinders	8
Aspiration	Natural Aspiration
Rated speed	1500 rpm
Gross power	121 kW

Generator sets powered by this engine

Shared across brands: Cummins/Onan, General Motors, Kohler, SDMO, Taylor Power

Cummins/Onan GGLB-5791965General Motors 8.1L PowertrainKohler 100REZG Kohler 125RZGKohler REZGSDMO G100 SDMO G110 SDMO G125U SDMO G130Taylor Power TGR70

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Replace air filter		—	500 hr
Fuel filter	Replace fuel filter		—	1000 hr
Oil filter	Replace oil filter		1.836	250 hr	buy
Battery	1, Crown 24-XD		24-XD		eBay
Belt	Drive Belt Tensioner		374176		Amazon eBay
Coolant	Change coolant and water pump	29.9	—	1000 hr
Coolant filter			—
Oil	Change oil and filter	7.1	—	250 hr
Spark plug	Replace spark plugs		2.270	10000 hr	buy

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Service intervals

Item	Action	Hours	Months	Notes
Battery	Other	250 hr	6 mo	Service battery.
Engine mounts	Check	250 hr	6 mo	Check tightness and vibration isolator condition
Engine oil and filter	Change	250 hr	6 mo	May extend to 375 hours with John Deere PLUS-50 oil and John Deere oil filter.
Fire extinguisher	Inspect	250 hr	1 mo	Inspect at least every 250 hours or once a month
Fire extinguisher	Other	250 hr	6 mo	Service fire extinguisher.
PTO clutch adjustment	Check	250 hr	6 mo
PTO clutch shaft bearings	Lubricate	250 hr	6 mo
Starter battery	Test	250 hr	6 mo	Service battery; check electrolyte and connections
Air intake hoses, connections and system	Check	500 hr	12 mo
Air intake hoses, connections, and system	Inspect	500 hr	12 mo
Automatic belt tensioner and belt wear	Check	500 hr	12 mo
Belt tension and manual tensioner	Check	500 hr		POWERTECH engines with manual tensioner
Coolant solution	Test	600 hr	12 mo	Analyze coolant; add SCAs as needed.
Cooling system	Check	500 hr	12 mo
Cooling system	Test	500 hr	12 mo	Pressure test cooling system.
Crankcase vent tube	Clean	500 hr	12 mo
Engine oil and oil filter	Change	500 hr	12 mo	First service — Then every 500 hours or at least once a year
Fuel filter element	Replace	500 hr	12 mo
PTO clutch internal levers and linkage	Lubricate	500 hr	12 mo
Automatic belt tensioner	Check	1000 hr	12 mo	POWERTECH engines when equipped
Cooling system	Other	2000 hr	24 mo	Flush cooling system; COOL-GARD may extend to 3000 hours/36 months or 5000 hours/60 months with annual testing and SCA replenishment.
Crankshaft vibration damper	Check	2000 hr	24 mo	6-cylinder engine only.
Engine valve clearance	Adjust	2000 hr		POWERTECH engines
Thermostats	Test	2000 hr	24 mo
Valve clearance	Adjust	2000 hr	24 mo
Cooling system	Drain	2500 hr	36 mo	With John Deere COOL-GARD; otherwise every 2000 hours/24 months
Crankshaft vibration damper (6-cylinder)	Replace	4500 hr	60 mo	Whichever occurs first
Injection nozzles	Replace	5000 hr
Thermostat	Replace	10000 hr
Air filter element	Replace		12 mo	After 6 cleanings or once a year
Paralleling box	Inspect		12 mo	Annually by a Kohler authorized distributor/dealer, or when wear, damage, deterioration, or malfunction is evident or suspected.
Paralleling box internal components	Inspect		1 mo	Monthly or when a condition noticed during external inspection may have affected internal components; enclosure cover must be removed by trained personnel.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Air cleaner neck to engine intake overlap	38	mm	1.5 in
Clearance	Belt deflection twist check	75-85	degrees	Twist belt in middle of 10-12 inch span
Clearance	Exhaust valve clearance adjustment	0.46	mm	engine cold; 0.018 in
Clearance	Exhaust valve clearance checking	0.41—0.48	mm	engine cold; rocker arm-to-valve tip
Clearance	Intake valve clearance adjustment	0.36	mm	engine cold; 0.014 in
Clearance	Intake valve clearance checking	0.31—0.38	mm	engine cold; rocker arm-to-valve tip
Gap	Spark Plug Gap	.060	in
Gap	Spark Plug Gap	1.52	mm
Other	10 in. weld flange bolt circle diameter B	361.95	mm (14.25 in.)
Other	10 in. weld flange outside diameter C	406.4	mm (16.0 in.)
Other	10 in. weld flange quantity of bolts / bolt hole diameter D	12, 25.40	mm (1.00 in.)
Other	12 V heavy duty starter cold cranking amps	800	CCA	At -18 C
Other	12 V standard duty starter cold cranking amps	640	CCA	At -18 C
Other	12 in. weld flange bolt circle diameter B	431.80	mm (17.00 in.)
Other	12 in. weld flange outside diameter C	482.6	mm (19.0 in.)
Other	12 in. weld flange quantity of bolts / bolt hole diameter D	12, 25.40	mm (1.00 in.)
Other	14 in. weld flange bolt circle diameter B	476.25	mm (18.75 in.)
Other	14 in. weld flange outside diameter C	533.4	mm (21.0 in.)
Other	14 in. weld flange quantity of bolts / bolt hole diameter D	12, 28.58	mm (1.13 in.)
Other	16 in. weld flange bolt circle diameter B	539.75	mm (21.25 in.)
Other	16 in. weld flange outside diameter C	596.9	mm (23.5 in.)
Other	16 in. weld flange quantity of bolts / bolt hole diameter D	16, 28.58	mm (1.13 in.)
Other	18 in. weld flange bolt circle diameter B	577.85	mm (22.75 in.)
Other	18 in. weld flange outside diameter C	635.0	mm (25.0 in.)
Other	18 in. weld flange quantity of bolts / bolt hole diameter D	16, 31.75	mm (1.25 in.)
Other	20 in. weld flange bolt circle diameter B	635.00	mm (25.00 in.)
Other	20 in. weld flange outside diameter C	698.5	mm (27.5 in.)
Other	20 in. weld flange quantity of bolts / bolt hole diameter D	20, 31.75	mm (1.25 in.)
Other	24 V standard duty starter cold cranking amps	570	CCA	At -18 C
Other	5 in. weld flange bolt circle diameter B	215.90	mm (8.50 in.)
Other	5 in. weld flange outside diameter C	241.30	mm (9.50 in.)
Other	5 in. weld flange quantity of bolts / bolt hole diameter D	8, 22.23	mm (0.88 in.)
Other	6 in. weld flange bolt circle diameter B	254.0	mm (10.0 in.)
Other	6 in. weld flange outside diameter C	279.4	mm (11.0 in.)
Other	6 in. weld flange quantity of bolts / bolt hole diameter D	8, 22.23	mm (0.88 in.)
Other	8 in. weld flange bolt circle diameter B	298.45	mm (11.75 in.)
Other	8 in. weld flange outside diameter C	342.9	mm (13.5 in.)
Other	8 in. weld flange quantity of bolts / bolt hole diameter D	8, 22.23	mm (0.88 in.)
Other	Auxiliary gear drive continuous operation limit	30	kW	At 2500 rpm
Other	Auxiliary gear drive intermittent operation limit	37	kW	At 2500 rpm
Other	Coolant drain interval with John Deere COOL-GARD	5000 hours or 5 years	hours/years	If coolant tested annually and additives replenished
Other	Coolant drain interval without COOL-GARD	2000 hours or 2 years	hours/years	Other coolant
Other	Coolant drain interval, factory fill	3000 hours or 3 years	hours/years	First drain
Other	Coolant test interval	600 hours or 12 months	hours/months	Or less; whenever excessive coolant is lost
Other	Engine speed adjustment	50		default setting; settings between 40 and 60 acceptable; 52 increases speed by 2 RPM, 49 decreases by 1 RPM
Other	Firing Order	1-8-7-2-6-5-4-3
Other	Generator to bus phase angle	-10 to 10	degrees	verify with contactor closed
Other	Ignition Control (IC) Circuit Frequency	3.0-20	Hz	DC Hertz scale
Other	Reactive droop	1	%	default setting; range 0.5 - 2%
Other	Spark Plug Type	TJ14R-P15		Denso plug type
Other	Tachometer binary code	10110011		30 pulses per revolution
Other	Test Light Amperage Draw	less than 3/10 amp (.3A)	amp	test light safe to use
Other	Weld flange angle A (10, 12, 14 in. nominal pipe size)	30	deg.
Other	Weld flange angle A (16, 18, 20 in. nominal pipe size)	22.5	deg.
Other	Weld flange angle A (5, 6, 8 in. nominal pipe size)	45	deg.
Pressure	Air restriction indicator vacuum	625	mm H2O	Replace primary element at this restriction
Pressure	Cooling system test	70	kPa	0.7 bar; 10 psi
Pressure	Engine oil pressure at full load	345 ± 103	kPa	At normal operating temperature, 115 C sump
Pressure	Fuel Pressure	379-427	kPa	fuel pump running
Pressure	Fuel Pressure	55-62	psi	fuel pump running

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Notes
Coolant	John Deere COOL-GARD Prediluted Coolant or COOL-GARD Concentrate 40-60% with quality water	ASTM D5345 prediluted or ASTM D4985 concentrate; low silicate ethylene glycol	50% ethylene glycol gives freeze protection to -37 C; do not use automotive-type coolant
Coolant	John Deere COOLANT CONDITIONER supplemental coolant additive		Replenish supplemental coolant additives as required; do not over-add
Coolant	low silicate, ethylene-glycol base antifreeze	John Deere COOL-GARD	Use TY16004 or TY16005 Liquid Coolant Conditioner; conditioner does not protect cooling system from freezing.
Engine oil	John Deere ENGINE BREAK-IN OIL	API CE or ACEA E1 if John Deere break-in oil unavailable	First 100 hours of new or rebuilt engine; part TY22041
Engine oil	John Deere PLUS-50 oil		Oil change interval may be extended by 50 percent to 375 hours with John Deere PLUS-50 oil and John Deere oil filter.
Engine oil	John Deere PLUS-50 preferred; John Deere TORQ-GARD SUPREME recommended	API CH-4, CG-4, CF-4; ACEA E3, E2	Use seasonal viscosity grade based on expected air temperature range between oil changes
Fuel	Diesel fuel; Grade No. 1-D below 5 C	EN 590 or ASTM D975; cetane minimum 40; sulfur maximum 0.5%; lubricity BOCLE minimum 3100 g	Do not use diesel fuel with sulfur greater than 1.0%; do not mix used oil with fuel
Fuel	Kerosene or No. 1 fuel oil		Indirect-fired oil heaters burn kerosene or No. 1 fuel oil (onboard tank)
Fuel	Regular unleaded gasoline, 87 octane or higher	American Automobile Manufacturers Association (AAMA) specification	Do not use methanol. General Motors does not recommend gasolines containing MMT. Never use leaded gasoline.
Fuel	diesel		Use proper type fuel for operating conditions.
Grease	John Deere Multipurpose Lubricant		For PTO clutch linkage pivot points and release lever shaft fittings.
Grease	John Deere SD POLYUREA GREASE preferred; HD MOLY, HD LITHIUM COMPLEX, HD WATER RESISTANT, GREASE-GARD also recommended	NLGI Performance Classification GC-LB	Consult supplier before mixing different grease thickeners
Grease	PT507 Multi-Purpose Grease		Lubricate new thermostat O-ring.
Hydraulic oil	biodegradable hydraulic fluid		All diesel-driven hydraulic power pack models utilize biodegradable hydraulic fluid to help protect the environment
Other	AR41785		Engine Storage Kit.
Other	AR41937		Nucle Oil for circulating through injection system during storage/ cranking.
Other	TY15161		Cooling System Sealer may be added to radiator to stop leaks; do not use other stop-leak additives.
Other	TY15979		John Deere Heavy Duty Cooling System Cleaner, or equivalent Fleetguard RESTORE/RESTORE PLUS.
Other	TY16004 or TY16005		Liquid Coolant Conditioner; recharge at 500 hours or 12 months.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Severity	Action
00-1	Generator set emergency stop
01-1	External emergency stop
02-1	Engine oil pressure
03-1	Engine water temperature
04-0	Daily fuel tank level low alarm
04-1	Daily fuel tank level low fault
05-1	Radiator water level low
06-0	Alternator overload or short-circuit alarm
06-1	Alternator overload or short-circuit fault
07-1	Engine overspeed
08-0	Min. battery voltage alarm
08-1	Min. battery voltage fault
09-0	Max. battery voltage alarm
09-1	Max. battery voltage fault
10-0	Lithium battery absent
11-1	Generator set no start
12	Diagnostic System Operating	DTC 12 indicates that the ECM's diagnostic system is operating.	Info	If DTC 12 is not indicated, consult the On-Board Diagnostic (OBD) System Check.
12-0	Min. alternator voltage alarm
12-1	Min. alternator voltage fault
13	Oxygen (O2) Sensor 1 Circuit Inactive	Heated oxygen sensor 1 circuit has developed an open.		Refer to the DTC 13 diagnostic tables (scan and non-scan).
13-0	Max. alternator voltage alarm
13-1	Max. alternator voltage fault
14	Engine Coolant Temperature (ECT) Sensor Circuit - Low Temperature Indicated	Sets if signal voltage indicates a coolant temperature below -30°C (-22°F).		Refer to DTC 14 diagnostic tables.
14-0	Min. alternator frequency alarm
14-1	Min. alternator frequency fault
15	Engine Coolant Temperature (ECT) Sensor Circuit - High Temperature Indicated	Sets if signal voltage indicates a coolant temperature above 130°C (266°F).		Refer to DTC 15 diagnostic tables.
15-0	Max. alternator frequency alarm
15-1	Max. alternator frequency fault
16-1	Option 3 module CAN bus
17-1	Option 4 module CAN bus
18-1	Option 5 module CAN bus
19-1	Option 6 module CAN bus
21	Throttle Position (TP) Sensor Circuit - High Signal Voltage Indicated	TP sensor signal voltage high.		Refer to DTC 21 diagnostic tables.
22	Throttle Position (TP) Sensor Circuit - Low Signal Voltage Indicated	TP sensor signal voltage low.		Refer to DTC 22 diagnostic tables.
22-1	Hardware watchdog
23	Intake Air Temperature (IAT) Sensor Circuit - Low Temperature Indicated	Sets if signal voltage indicates an intake air temperature below -30°C (-22°F).		Refer to DTC 23 diagnostic tables.
24	Vehicle Speed Sensor (VSS) Circuit Inactive	VSS circuit is inactive.		Refer to DTC 24 diagnostic tables. DTC 24 may be intermittent.
25	Intake Air Temperature (IAT) Sensor Circuit - High Temperature Indicated	Sets if signal voltage indicates an intake air temperature above 130°C (266°F).		Refer to DTC 25 diagnostic tables.
25-0	Normal contactor open (system side)
26-0	Emergency contactor open (generating set side)
27-1	Oil temperature
28-1	Oil level low
29-0	No water preheating alarm
29-1	No water preheating fault
30-0	Differential trigger alarm
30-1	Differential trigger fault
31	Governor System Inactive	Governor system inactive.
31-0	Permanent insulation monitor trigger alarm
31-1	Permanent insulation monitor trigger fault
32	Exhaust Gas Recirculation (EGR) Valve Circuit Inactive	EGR valve circuit inactive.
32-1	Differential relay connection
33	Manifold Absolute Pressure (MAP) Sensor Circuit - High Signal Voltage Indicated	MAP sensor signal voltage high.		Refer to DTC 33 diagnostic tables.
33-1	Permanent insulation monitor connection
34	Manifold Absolute Pressure (MAP) Sensor Circuit - Low Signal Voltage Indicated	MAP sensor signal voltage low.		Refer to DTC 34 diagnostic tables.
34-0	Battery charger fault alarm
34-1	Battery charger fault shutdown
35-1	Air cooler trip
36-1	Air cooler low level
37-0	Fuel pump 1 trip alarm
37-1	Fuel pump 1 trip fault
38-0	Retention tank alarm
38-1	Retention tank fault
39-0	Fuel tank low level alarm
39-1	Fuel tank low level fault
40-1	Water flow
41	Ignition Control (IC) A Fault	Sets when the IC circuit is out of range for ignition coil 1.		Refer to DTC 41 diagnostic tables. If all IC DTCs set at the same time, inspect the IC ground circuits for an open.
41-1	Fire detection
42-1	Oil leak
43-1	Fuel leak
44	Knock Sensor (KS) 1 Circuit Inactive	Sets if the ECM does not see any activity on the KS signal circuits.		Refer to DTC 44 diagnostic tables.
44-1	Air cooler compartment door open
45-1	MCPS door open
46-0	Main circuit breaker open alarm
46-1	Main circuit breaker open fault
47-0	Overload
48-1	MTU engine oil pressure
49-1	MTU engine HV water temperature
50-1	MTU engine overspeed
51	Calibration Checksum Failure	The ECM checks for a calibration failure by comparing the calibration value to a known value stored in the EEPROM.		If DTC 51 failed more than once but is intermittent, replace the ECM; otherwise replace or reprogram the faulty ECM.
51-1	MTU engine general fault

Showing the first 80 of 116 codes.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

Calibration adjustment

⚠ Copying personality profiles from one controller to another can overwrite calibration coefficients and requires re-calibration.

Tools: Calibrated multimeter with recent calibration verification

Use a calibrated multimeter to measure the generator voltage and enter the correct value in the CONTROLLER CONFIG -> CALIBRATION screen.
Use a calibrated multimeter to measure the bus voltage and enter the correct value in the CONTROLLER CONFIG -> CALIBRATION screen.

Check and Adjust Valve Clearance adjustment

⚠ Valve clearance must be checked and adjusted with engine cold.

Tools: JDE83 or JDG820 Flywheel Turning Tool, JDE81-4 Timing Pin, Feeler gauge

Disconnect negative battery terminal.
Remove rocker arm cover and crankcase ventilator tube.
Remove timing hole plugs; rotate engine to No. 1 TDC compression.
Insert JDE81-4 timing pin in flywheel.
Check intake and exhaust valve clearances with engine cold.
Loosen jam nut and adjust screw until feeler gauge drags slightly.
Hold screw, tighten jam nut to 27 N•m (20 lb-ft), recheck clearance.
Repeat for remaining valves per 4- or 6-cylinder sequence.

Manual belt tensioner adjustment adjustment

⚠ Do not pry against alternator rear frame.

Tools: JDG1341 belt tension gauge

Install JDG1341 belt tension gauge halfway between pulleys.
Loosen cap screws B and C.
Slide alternator or tensioner bracket by hand to remove slack.
Pry outward on alternator front frame or tensioner bracket to stretch belt.
Stretch until specified tension is achieved.
Tighten cap screws B and C.
Run engine ten minutes and recheck used belt tension.

Clearing Diagnostic Trouble Codes - Non Scan diagnostic

⚠ The ignition must be cycled to OFF after codes are cleared or the DTCs will not clear.

Tools: Diagnostic Trouble Code (DTC) tool

Install Diagnostic Trouble Code (DTC) tool.
Ignition ON, engine OFF.
Switch DTC tool to service mode or ON.
Move the throttle from 0% (idle) to 100% (WOT) and back to 0%.
Switch DTC tool to normal mode or OFF.
Turn ignition OFF for at least 20 seconds.
Ignition ON, engine OFF.
Switch DTC tool to service mode or ON and verify DTC 12 only. Remove DTC tool.
If original DTCs are still present, repeat the DTC clearing procedure.
If new DTCs are displayed, perform the OBD system check.

Pressure Testing Cooling System diagnostic

⚠ Explosive release of fluids from pressurized cooling system can cause serious burns.

Tools: D05104ST Tester

Remove radiator cap and attach to D05104ST tester.
Pressurize cap to 70 kPa (0.7 bar) (10 psi).
Gauge should hold pressure for 10 seconds.
Retest cap turned 180 degrees to verify.
Connect gauge and adapter to radiator filler neck.
Pressurize system to 70 kPa and check for leaks.

Testing Thermostats Opening Temperature diagnostic

⚠ Do not let thermostat or thermometer rest against container side or bottom.

Tools: Thermometer, Container

Remove thermostat(s) and inspect for corrosion or damage.
Suspend thermostat and thermometer in water.
Stir water as it heats and observe opening action.
Compare opening temperatures with specification chart.
Remove thermostat and observe smooth closing as it cools.
Replace defective thermostat; replace dual thermostats as matched set.

Verify Generator Operation diagnostic

⚠ Generators must all operate at the same frequency, voltage, and phase connection in order to parallel.

Tools: SiteTech software

Ensure the load is not connected or is drawing less power than a single generator can provide.
Navigate to CONTROLLER CONFIG -> COMMUNICATION SETUP and verify PGEN Nodes Online indicates the correct number of nodes.
Verify alternator connection (voltage selector switch position), system voltage, and voltage regulator target on each generator.
Start a single generator by pressing the Run button; the paralleling box contactor should close and the Generator Connected to Bus indicator should light.
Verify bus and generator voltages match and generator to bus phase angle is between -10 and 10 degrees.
Verify the load bus is energized and available at the load.
Stop the generator by pressing the OFF button; the contactor should open.
Repeat for each generator in the paralleling system.

Verify Paralleling and Load Sharing diagnostic

Tools: Load bank (optional)

Place all generators in automatic mode by pressing the Auto button; verify the red shutdown indicator is not illuminated.
Provide a local start request by holding AUTO, pressing RUN, releasing RUN, then releasing AUTO.
Verify all generators start, one generator closes its contactor, and the others synchronize and close their contactors.
Verify that the % of rated power of the generators matches, showing the generators are sharing load equally.
If a load bank is available, test the system under load.

Common Hardware Application installation

Determine entry hole type: round or slotted.
Determine exit hole type: fixed female thread (weld nut), round, or slotted.
For round and slotted exit holes, determine if hardware is greater than 1/2 inch in diameter.
Hardware greater than 1/2 inch in diameter uses a standard nut and SAE washer.
Hardware 1/2 inch or less in diameter can use a properly torqued whiz nut or spiralock nut.
Always use a washer between hardware and a slot.
Always use a washer under a nut.
Use a washer under a bolt when the female thread is fixed (weld nut).

Control Harness Connections installation

⚠ The control harness connections for GEN 1 and GEN 2 must correspond to the source camlock cable connections.

Connect the control harness from the generator set connected to the GEN 1 camlock connectors to GEN 1 CONTROL.
Connect the control harness from the generator set connected to the GEN 2 camlock connectors to GEN 2 CONTROL.
When not used, store the control harnesses on the storage rack inside the enclosure.

Grounding installation

⚠ Grounding electrical equipment: hazardous voltage can cause severe injury or death. Turn off the main circuit breakers of all power sources before servicing.

Connect the ground lug on the paralleling box to earth ground according to applicable state and local codes.
Follow NEC guidelines for grounding electrical equipment.
The neutral is bonded to ground inside the paralleling box; if required, remove the bonding bus to disconnect neutral from ground.

Hitching trailer installation

⚠ Towing with a non-matching device can cause serious accidents.

Lock wheels to stop trailer moving.
Lift rear trailer supports and lock them.
Release parking brake.
Release draw bar arm locking levers and adjust ring to vehicle hook height.
Hitch trailer and remove wheel locks.
Lift front wheel fully using its handle.
Connect trailer electrical circuit to tow vehicle.
Hook handbrake safety wire onto tow vehicle hook.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
		12-Lead		Alternator Reconnections diagram ADV-5875B-M (page 16)
		4-Lead		Alternator Reconnections diagram ADV-5875A-M (page 15)
110-120	1	G	T1-T12	Winding 6/7/8. R 230 sensing 0=>T8 / 110 V=>T11; R 438 sensing 0=>T3 / 110 V=>T2.
120/208	3	12 LEAD LOW WYE	12	Model 100FPG4
120/240	1	12 LEAD ZIG-ZAG	12	Model 100FGG4; derate 12-wire single phase 240 volt to 97 kW standby and 78 kW prime
120/240	1	4 LEAD	4	Model 100FDG4
120/240	3	12 LEAD HI DELTA	12	Model 100FJG4
190-208 (60 Hz) / 190-240 (50 Hz)	3	A	T1-T12	Winding 6/7/8. R 230 sensing 0=>T8 / 110 V=>T11; R 438 sensing 0=>T3 / 220 V=>T2.
220-240	1	M	T1-T12	Winding 6/7/8. R 230 sensing 0=>T8 / 110 V=>T11; R 438 sensing 0=>T3 / 220 V=>T2.
220-240	1 or 3	FF	T1-T12	Winding 6/7/8. R 230 sensing 0=>T1 / 110 V=>T4; R 438 sensing 0=>T10 / 220 V=>T1.
220/230/240 L-L; 110/115/120 L-M	1	M or M1 dedicated 4-wire	T2-T3, T2-T3, T1-T4	Single-phase 4-wire; parallel connection not possible with LSA 44.2.
277/480	3	12 LEAD HI WYE	12	Model 100FRG4
347/600	3	4 LEAD WYE	4	Model 100FNG4
380-415 (50 Hz) / 380-480 (60 Hz)	3	AR	T1-T12	Winding 6/7/8. R 230 sensing 0=>T8 / 110 V=>T11; R 438 sensing 0=>T3 / 380 V=>T2.
480	3	12 lead reconnectable	12	Generator end is 12 lead reconnectable; generator end has PMG permanent magnet generator

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Parts cataloged across the General Motors 8.1L family

165

Part #	Description	Category
0D5420	AIR FILTER (NOT SHOWN)	Air filter
85400737	OUTER AIR FILTER	Air filter
85400786	INNER AIR FILTER	Air filter
85403921	AIR FILTER HEAVY DUTY	Air filter
0A1232	D.C. ALTERNATOR ASSY	Alternator
85402451	VOLTAGE REGULATOR	Avr
0A4278C	BELT, SERPENTINE	Belt
0A4278D	BELT, SERPENTINE 75.0" LG (G/B TURBO)	Belt
374176	Drive Belt	Belt
85425460	BELT	Belt
NGE012014	Charge Air Cooler Bolts	Bolt
375105	Clutch Pilot Bearing Removal (C/K/C3500HD)	Clutch pilot bearing removal
470627	Clutch Pilot Bearing Removal (Medium Duty)	Clutch pilot bearing removal
373133	Clutch Pilot Bearing Removal Tools Required	Clutch pilot bearing removal tools required
640014	Crankshaft Balancer Removal Steps	Crankshaft balancer removal steps
640013	Crankshaft Balancer Removal Tools Required	Crankshaft balancer removal tools required
638596	Cylinder Head and Components	Cylinder head and components
638608	Engine Crankshaft and Components	Engine crankshaft and components
470599	Engine Flywheel Housing Removal (Medium Duty with AT)	Engine flywheel housing removal
470572	Engine Flywheel Removal (C/K/C3500HD with AT MT1)	Engine flywheel removal
470576	Engine Flywheel Removal (Medium Duty with MT)	Engine flywheel removal
677814	Engine Flywheel Removal (C3500HD with AT M74)	Engine flywheel removal
679414	Engine Flywheel Removal (C/K with MT)	Engine flywheel removal
677764	Engine Identification Number	Engine identification number
1052367	Engine Oil Supplement Lubricant	Fluid
85403756	BATTERY ELECTROLYTE	Fluid
9985770	MAP Sensor Seal Lubricant	Fluid
GM16430	Sealer, oil pan / Sealant, Loctite	Fluid
GM18888	Sealer, crankshaft rear main bearing	Fluid
GM18933	Sealer, camshaft bearing hole plug	Fluid
GM18934	Grease, heavy duty multipurpose	Fluid
638592	Flywheel Housing Adapter, Medium Duty with Manual Transmission	Flywheel housing adapter
85400976	FUEL FILTER	Fuel filter
85403525	FUEL FILTER SEPARATOR	Fuel filter
85431120	FUEL FILTER	Fuel filter
055466	GASKET-EXH MANIFOLD	Gasket
0C6960	GASKET, THERM 3LHA	Gasket
0C81660121	GASKET, WATER PUMP	Gasket
0C81660124	GASKET, ENG FRT COVER	Gasket
0C81660142	GASKET, OIL PAN	Gasket
0C81660168	GASKET, ENG COOL C/OVR PIPE	Gasket
0C81660200	GASKET VLV RKR ARM CVR	Gasket
0C81660203	GASKET, VLV RKR ARM CVR	Gasket
0C81660226	GASKET, CYL HEAD LH	Gasket
0C81660227	GASKET, CYL HEAD RH	Gasket
0C81660253	GASKET, EGR VLV PIPE	Gasket
0C81660263	GASKET KIT, INT MANIF (NOT SHOWN)	Gasket
0C9786	GASKET-MANIFOLD INTAKE	Gasket
85401131	ROCKER COVER GASKET	Gasket
GM18951	Gasket, engine front cover, also part of 76	Gasket
GM18963	Gasket, water pump	Gasket
GM18964	Gasket, engine coolant crossover	Gasket
GM19009	Gasket, oil pan	Gasket
047290	HOSE 3/8 ID SINGLE BRAID (16” LG)	Hose
083982	HOSE 3/8 ID 100R6 OIL LINE	Hose
0C81660159	HOSE, THERM BYPASS (INCL CLAMPS)	Hose
0C81660262	HOSE, FUEL PRESS REG VAC	Hose
0E5353	HOSE,90DEG PREFORMED 3/8" I.D.	Hose
0E5362	HOSE,90DEG PREFORMED 3/4" I.D.	Hose
85401289	RADIATOR TOP HOSE	Hose
85426005	RADIATOR BOTTOM HOSE	Hose
GM18967	Hose, therm bypass includes hose clamps	Hose
S105	Ignition Coil (cylinders #8)	Ignition coil
S107	Ignition Coil (cylinders #1, #3 & #5)	Ignition coil
85400893	INJECTOR	Injector
638602	Intake Manifold and Components	Intake manifold and components
638616	Lower Engine Block and Components	Lower engine block and components
0C81660135	OIL FILTER	Oil filter
36881696	ELEMENT, ENGINE OIL FILTER	Oil filter
GM16703	Filter, oil	Oil filter
470639	Oil Level Indicator and Tube Removal (C/K/C3500HD)	Oil level indicator and tube removal
470666	Oil Level Indicator and Tube Removal (G)	Oil level indicator and tube removal
022676	FUSE AGC-15A.	Service part / kit
0333-0588-03	Coolant heater, 1500W, 120V	Service part / kit
0C81660100	RING KIT, PISTON, STD	Service part / kit
0C81660101	RING KIT, PISTON, O.S. 0.030"	Service part / kit
0C81660107	BEARING KIT, CONN ROD	Service part / kit
0C81660126	BEARING KIT, CR/SHF	Service part / kit
0C81660127	BEARING KIT, CR/SHF THRUST	Service part / kit
0C81660180	PIN, 1/4 X 5/8	Service part / kit
0C81660215	VALVE, INT (STD)	Service part / kit
0C81660219	VALVE, EXH (STD)	Service part / kit
0C81660223	LIFTER, VALVE	Service part / kit
0C81660245	COIL, IGNITION	Service part / kit
0D2031	TENSIONER PULLEY	Service part / kit
0E4149	IGN CON (MEFI-4) 8.1GM D/D PGM	Service part / kit
0E5355	ASSY, AIR/OIL SEPERATOR	Service part / kit
1051396	Engine Oil Supplement Lubricant	Service part / kit
1052942	Crankshaft Rear Bearing Cap Sealant	Service part / kit
12377901	Camshaft Rear Bearing Hole Plug Sealant	Service part / kit
22307	Test Light Amperage Draw Test	Service part / kit
24-XD	Battery, Crown 24-XD	Service part / kit
39200	DVOM J 39200	Service part / kit
85401081	COOLANT HEATER RESISTANCE 1000W 240V	Service part / kit
85403616	ELECTRONIC ACTUATOR	Service part / kit
85403731	STARTING BATTERY 12V 100Ah 450A	Service part / kit
85404267	AIR HEATER RESISTANCE 1200W 12V	Service part / kit
85409530	3 WAY FUEL VALVE	Service part / kit
85410249	AIR SHUT OFF VALVE D51	Service part / kit
85425585	SURGE SUPPRESSOR	Service part / kit
85425593	DIODE BRIDGE	Service part / kit
85425908	BEARING	Service part / kit
85425932	DRIVE DISC	Service part / kit
85426260	ELECTRONIC GOVERNOR 12VCC	Service part / kit
85500635	WATER RADIATOR	Service part / kit
C109	Ignition Control Ground	Service part / kit
C110	Ignition Control Ground	Service part / kit
GM23005-5	Coolant heater, Hotstart, 1500W, 120V	Service part / kit
GM28341	Battery charger, 120V, 1.6A	Service part / kit
LG199	Home Maintenance Kit	Service part / kit
0C81660122	PUMP KIT, WATER (INCL ITEMS 31,82,83,85,105)	Pump
0C81660138	PUMP, OIL (W/SCRN)	Pump
85401313	WATER PUMP	Pump
85403434	MANUAL PUMP	Pump
GM18990	Pump, oil with screen	Pump
GM19027	Pump kit, water (incl. 31, 82, 83, 85, 105)	Pump
470515	Repair Instructions - Draining Fluids and Oil Filter Removal	Repair instructions
0A37970217	SEAL, OIL PAN DRN PLUG	Seal
0C81660128	SEAL, CR/SHF RR OIL	Seal
0C81660148	SEAL, CR/SHF FRT OIL	Seal
0C81660162	SEAL, ENG COOL THERM (O-RING)	Seal
0C81660237	SEAL, VALVE STEM OIL	Seal
0C81660261	SEAL, MAP SEN	Seal
85401206	THERMOSTAT SEAL	Seal
GM16576	Seal, oil pan drain plug	Seal
GM18971	Seal, crankshaft rear oil	Seal
GM18972	Seal, crankshaft front oil	Seal
035606	SENSOR HI COOLANT SHUTDOWN	Sensor
053666	SENDER OIL PRESSURE	Sensor
053667	SENDER WATER TEMP	Sensor
0A8584	Switch	Sensor
0C81660171	SENSOR, CM/SHF POSN	Sensor
0C81660172	SENSOR, CR/SHF POSN	Sensor
0C81660174	SENSOR, KNOCK	Sensor
0C81660260	SENSOR, MAP	Sensor
0D2244M	ASSY MAGPICKUP (3/8-24 MALE)	Sensor
0E0561	ASSY WATER LEVEL SENSOR C/E PL	Sensor
0E7590	MAP SENSOR 2 ATMOSPHERE (8.1L DIRECT DRIVE TURBO)	Sensor
290090	Switch, low water temperature	Sensor
416E	Manifold Absolute Pressure (MAP) sensor circuit - CKT 416E	Sensor
85401099	PRESSURE SWITCH	Sensor
85401164	TEMPERATURE SWITCH	Sensor
85403632	MAGNETIC SPEED SENSOR L75 3/4UNF	Sensor
85404572	LEVEL SENSOR	Sensor
85404598	PRESSURE SWITCH 00/10 BAR	Sensor
85404606	TEMPERATURE SENSOR 40/120°	Sensor
85410108	AIR RESTRICTION INDICATOR	Sensor
GM18906	Sensor, knock	Sensor
GM18952	Sensor, crankshaft position (includes 123)	Sensor
GM19004	Sensor, camshaft position (2001 GM engines / GM model year 2003 and older)	Sensor
GM24739	Sensor, camshaft position (2002 and 2003 GM engines)	Sensor
GM51539	Sensor, camshaft position (2004-- GM engines)	Sensor
GM75077	Sensor, Cm/Shf Posn (GM model year 2004 and newer)	Sensor
MEFI4309	Map Sensor 1	Sensor
MEFI4310	Knock Sensor (KS) 1	Sensor
MEFI4313	Heated Oxygen (HO2) Sensor 1	Sensor
0C81660212	SPARK PLUG	Spark plug
0E0307	SPARK PLUG WIRE SET	Spark plug
TJ14R-P15	Denso plug type	Spark plug
059056A	STARTER	Starter
0C81660163	THERMOSTAT, ENG COOL	Thermostat
85401180	THERMOSTAT	Thermostat
GM42165	Thermostat, block heater 49C--60C (120F--140F)	Thermostat
0E4149B	IGN CON (MWFI-4) 8.1GM (D/D TURBO)	Turbocharger
0E4149C	IGN CON (MEF1-4) 8.1GM (G/B TURBO)	Turbocharger

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

What is the oil capacity of the General Motors 8.1L?

The General Motors 8.1L engine has an oil capacity of 10.0 liters.

What is the displacement of the General Motors 8.1L?

The General Motors 8.1L has a displacement of 8.1 liters with 8 cylinders.

Which generators use the General Motors 8.1L engine?

The General Motors 8.1L powers 10 generator set(s), including Cummins/Onan GGLB-5791965, General Motors 8.1L Powertrain, Kohler 100REZG, Kohler 125RZG, Kohler REZG.

How often should you change the oil in the General Motors 8.1L?

The General Motors 8.1L oil change interval is every 250 hours.