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Cummins/Onan J Series Engine

The Cummins/Onan J Series is a 4-cylinder naturally aspirated engine rated at 1800 rpm. It holds 6.15 L (1.6 gal) of oil and 11.4 L (3.0 gal) of coolant.

Also known as: Onan J Series

Cylinders

1800 rpm

Rated speed

6.15 L

Oil capacity

On this pageSpecs Maintenance FAQ Service intervals Torque & specs Fluids Procedures Wiring

Engine specifications

Oil capacity	6.15 L
Coolant capacity	11.4 L
Cylinders	4
Aspiration	Naturally Aspirated
Rated speed	1800 rpm

Generator sets

No generator set in our catalog cites this exact engine designation yet; its specifications and fault codes are documented here.

How to read your Cummins/Onan engine serial & model number →

Troubleshooting

Fault codes

Code	Meaning
e008	No specific name provided for e008
10	Overload

Fault codes and symptom→remedy steps extracted from this engine’s service/owner documentation; verify against the official manual before servicing.

Common problems

Engine runs, shuts down and LOW OIL PRESSURE Lamp lights
Cause: Possible fuel or ignition system problem: empty fuel tank, fuel or leaks, or plugged fuel lines
Fix: Check for empty fuel tank, fuel or leaks, or plugged fuel lines and correct as required
Cranking Limiter pops out and engine stops cranking. ENGINE FAILURE TO START lamp lights
Cause: Possible fuel or ignition system problem: empty fuel tank, fuel or leaks, or plugged fuel lines
Fix: Check for empty fuel tank, fuel or leaks, or plugged fuel lines and correct as required
Engine will not crank
Cause: Fault lamp on
Fix: Correct fault and reset control
Thermostat does not start to open when suspended in water at 150°F or does not close within a short time after being removed from hot water.
Fix: Replace thermostat if it is broken, corroded, or sticks in open or closed position. If engine overheats or does not reach and maintain a minimum operating temperature, thermostat should be removed and tested as a possible cause.
Pressure cap malfunctions.
Fix: Inspect pressure cap periodically for freedom of operation, and gasket should be checked for proper sealing. Replace pressure cap if it malfunctions.
No build up of AC output voltage — Replace voltage regulator PC board (VR21)
Fix: Replace voltage regulator PC board (VR21)
No build up of AC output voltage — Reconnect generator leads 1 & 2 to TB21-1 and TB21-2 on VR22. Does reference voltage build up?
Fix: Proceed to step 15 if YES; proceed to step 13 if NO
No build up of AC output voltage — Push to reset Field Breaker. Does AC output voltage build up?
Fix: If voltage builds up but is high, low, unstable, or causes tripping of Field Breaker, refer to Tables B, C, or D
No build up of AC output voltage — Is regulator DC output voltage across VR21-7 and VR21-8 7 VDC or more?
Fix: Proceed to step 16 if YES; proceed to step 18 if NO
No build up of AC output voltage — Is Field Breaker CB21 on control panel ON?
Fix: Proceed to step 2 if YES; proceed to step 3 if NO
No build up of AC output voltage — Is exciter field voltage across F1+ and F2- on endbell terminal block 7.0 VDC or more?
Cause: Wiring harness W9 from end bell to VR22 terminals 3 and 4 may be faulty
Fix: If not, check wiring harness W9 from end bell to VR22 terminals 3 and 4
No build up of AC output voltage — Flash exciter field. Is reference voltage across 1 and 2 now 20 VAC or more?
Fix: Proceed to step 14 if YES; proceed to step 13 if NO
No build up of AC output voltage — Disconnect alternator stator leads 1 & 2 from TB21-1 and TB21-2 on VR22. Is reference voltage across 1 & 2 20 VAC or more?
Fix: Proceed to step 14 if YES; proceed to step 13 if NO
No build up of AC output voltage — Connect jumper wire across terminals of Field Breaker, CB21. Does AC output voltage build up?
Cause: Field breaker defective
Fix: If voltage builds up REPLACE FIELD BREAKER; if not, proceed to step 4
No build up of AC output voltage — Are SCR's CR13 and CR16 OK?
Fix: Proceed to step 17 if YES; proceed to step 18 if NO

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan J Series.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter	Polyurethane foam air cleaner element		—	50 hr
Fuel filter	Fuel filter with sediment bowl		—	100 hr
Oil filter	Spin-on oil filter		—	500 hr
Battery	12V, 105 Ah battery		—	1000 hr
Belt	Drive belts and fan belt, deflection 0.5 in at 15 lbs force		—	500 hr
Coolant	Rust inhibitor and water or 50/50 antifreeze mix	11.4 L	—	500 hr
Oil	API SF/CD, 20W-40 or 20W-50 at 60-100F	6.15 L	—	500 hr
Spark plug	Spark plug, gap 0.035 in (0.89 mm)		—	1000 hr

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
Exhaust system	Inspect	8 hr		Maintenance schedules recommend inspection every eight hours by owner/operator for RV generator set exhaust systems.
Cylinder head bolts	Adjust	50 hr		First service — After the first 50 hours of operation, retighten the cylinder head bolts and check valve clearance
Fuel Tank Water and Sediment	Drain	50 hr		Every 50 Service Hours or Weekly
Spark arrester/muffler, screen type	Clean	50 hr		Remove and scrape clean or replace screen; may be blown clean with compressed air. Every 50 operating hours.
Spark arrester/muffler, spin-out type	Clean	50 hr		Remove pipe plug in bottom of muffler and run set for 5 minutes; replace plug. Every 50 hours of set operation.
Spark arresters	Clean	50 hr		Spark arresters should be cleaned every 50 to 100 hours; routine cleaning during servicing is good safety practice.
Spark plugs	Replace	75 hr		Annually or every 75 hours, whichever occurs first, for B43M/B48M/BF/BG/N52M engines.
Air cleaner (dry paper cartridge)	Clean	100 hr		Clean at least every 100 hours; do not wash
Battery	Check	100 hr		Check battery water level and charge condition about every 100 hours
Air cleaner (foam element)	Clean	200 hr		About every 200 hours; replace only if damaged
Oil filter	Replace	200 hr		Replace normally after every 200 hours of operation
Air cleaner (dry paper cartridge)	Replace	500 hr		Replace cartridge at least every 500 hours
Battery Electrolyte Level	Check	500 hr	12 mo	Every 500 Service Hours or 1 Year
Engine Air Cleaner Element (Dual Element)	Clean	500 hr	12 mo	Every 500 Service Hours or 1 Year - Clean/Replace
Engine Air Cleaner Element (Single Element)	Inspect	500 hr	12 mo	Every 500 Service Hours or 1 Year - Inspect/Replace
Engine Ground	Inspect	500 hr	12 mo	Every 500 Service Hours or 1 Year - Inspect/Clean
Engine Oil and Filter	Change	500 hr	12 mo	Every 500 Service Hours or 1 Year
Fuel System Primary Filter (Water Separator) Element	Replace	500 hr	12 mo	Every 500 Service Hours or 1 Year
Fuel System Secondary Filter	Replace	500 hr	12 mo	Every 500 Service Hours or 1 Year
Hoses and Clamps	Inspect	500 hr	12 mo	Every 500 Service Hours or 1 Year - Inspect/Replace
Radiator	Clean	500 hr	12 mo	Every 500 Service Hours or 1 Year
Stainless steel spark arrester screen	Replace	500 hr		For units using specially designed stainless steel screens.
Starting system wiring	Inspect	500 hr		Every 500 hours inspect all starting system wiring for loose or dirty connections
Engine Valve Lash	Inspect	1000 hr		Every 1000 Service Hours - Inspect/Adjust
Aftercooler Core	Inspect	2000 hr		Every 2000 Service Hours
Alternator	Inspect	2000 hr		Every 2000 Service Hours
Engine Mounts	Inspect	2000 hr		Every 2000 Service Hours
Starting Motor	Inspect	2000 hr		Every 2000 Service Hours
Turbocharger	Inspect	2000 hr		Every 2000 Service Hours
Water Pump	Inspect	2000 hr		Every 2000 Service Hours
Cooling System Coolant (Commercial Heavy-Duty)	Change	3000 hr	24 mo	Every 3000 Service Hours or 2 Years
Fuel Injector	Test	3000 hr		Every 3000 Service Hours - Test/Change
Aftercooler Core	Clean	4000 hr		Every 4000 Service Hours - Clean/Test
Cooling System Coolant Extender (ELC)	Other	6000 hr	36 mo	Every 6000 Service Hours or 3 Years - Add
Cooling System Coolant (ELC)	Change	12000 hr	72 mo	Every 12 000 Service Hours or 6 Years
Cooling System Coolant	Change		24 mo	Every 2 Years
Cooling system	Clean		12 mo	Clean and flush at least once a year
Flexible fuel lines	Replace		60 mo	Replace every five years as a precautionary measure; check at each service.
Zinc pencil	Inspect		2 mo	Inspect at least every two months; replace if deteriorated to less than one half original size

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	Camshaft end play (new)	0.10 to 0.55	mm (0.004 to 0.022 inch)	Maximum permissible end play of a worn camshaft 0.60 mm (0.023 inch)
Clearance	Clearance between the bearing shell and the main bearing journals	0.057 to 0.117	mm (0.0022 to 0.0046 inch)
Clearance	Connecting rod bearing clearance	0.030 to 0.081	mm (0.0012 to 0.0032 inch)
Clearance	Cylinder bore	105.000 to 105.025	mm (4.1338 to 4.1348 inch)
Clearance	Cylinder head thickness	117.95 to 118.05	mm (4.643 to 4.647 inch)	Minimum thickness 117.20 mm (4.614 inch)
Clearance	Distributor shaft end play	0.003-0.010	in
Clearance	Front gear cover oil seal installation depth	1-1/32	in	rear spring side of casing from gear cover mounting face
Clearance	Fuel injection pump installation dimension	3.260	in	new camshaft; instead of 3.254
Clearance	Maximum permissible wear for the cylinder bore	0 to 0.15	mm (0 to 0.0059 inch)
Clearance	Original size of the connecting rod bearing journal	63.47 to 63.49	mm (2.4988 to 2.4996 inch)
Clearance	Original size of the main bearing journal	76.159 to 76.180	mm (2.9984 to 2.9992 inch)
Clearance	Prestolite starting motor pinion clearance to pinion stop	0.070-0.120 (1.78-3.05)	in (mm)	solenoid plunger bottomed
Clearance	Starter gear lash	.020 - .010	in	pinion/ring gear engagement
Clearance	Starting motor armature end play	0.005-0.030 (0.127-0.762)	in (mm)
Clearance	Valve guide inside diameter	9.000 to 9.022	mm (0.3543 to 0.3552 inch)
Clearance	Water pump impeller clearance (A-A)	zero to 1/16 (1.6)	in (mm)	with drive belt off
Gap	Breaker point gap - static (full separation and engine cold)	0.020 (0.51)	in (mm)	full separation, engine cold
Gap	Centrifugal switch point gap	0.040	inches
Gap	Point gap	0.016	in	equals 20 degrees BTC ignition timing and spark advance
Gap	Spark plug gap	.035	in	increased from .025 (0.64 mm) for light-load smoothness
Gap	Spark plug gap (MJB)	0.025 (0.64)	in (mm)
Gap	Spark plug gap (MJC/RJC)	0.035 (0.89)	in (mm)
Gap	Start disconnect point gap	0.020 (0.51)	in (mm)
Other	Battery specific gravity when 75 percent charged	1.290 to 1.225		75 percent charged
Other	Bosch EPVE fuel injection pump plunger lift	1.55	mm (0.0610 inch)
Other	Breaker point spring tension	17-20	ounces	rubbing block off the cam
Other	Carburetor main jet adjustment	1-1/2 to 1-3/4	turns open	NHC-MS normal adjustment
Other	Connecting rod torx screws - additional turn	120	degrees
Other	Cranking limiter limits cranking time	45 to 90	seconds	depending on ambient temperature
Other	Cylinder head bolts - additional turn (long bolts)	270	degrees
Other	Cylinder head bolts - additional turn (short bolts)	225	degrees
Other	Ignition timing with spark advance	24	degrees BTC	after initial timing change to 5 degrees BTC
Other	Initial ignition timing	5	degrees BTC	CCKB-MS/2861J and CCKB-MS/2900J magneto ignition with electric start
Other	Injection timing advance	2	crank degrees	4-cylinder J Series diesel; advance from 19 to 21 degrees BTC PC
Other	Piston height above cylinder block	0.21 to 0.35	mm (0.008 to 0.014 inch)
Other	Rotor diameter	4.420	in	acceptable; replace rotors measuring 4.415 in or less
Other	V-belt tension	535	N (120 lb)	Initial belt tension; used belt tension 355 N (80 lb)
Other	Voltage adjust rheostat adjustment	plus or minus 5	percent
Other	Water temperature regulator minimum stroke at full open temperature	10	mm (0.3937 inch)
Pressure	Compression (new engine cranking at about 300 rpm)	about 100	psi	cranking at about 300 rpm
Pressure	Cylinder compression variation limit between cylinders	350	kPa (51 psi)
Pressure	Engine oil pressure minimum at maximum engine speed and normal operating temperature	300	kPa (43 psi)	at maximum engine speed, normal operating temperature
Pressure	Expansion tank fill cap (marine)	12-15	psi
Pressure	Fuel injector service setting injection pressure	29.4 ± 0.8	MPa (4264 ± 116 psi)	Leakage in 10 seconds = 0 drops
Pressure	Fuel pressure at idle (all fuel injection pumps)	25	kPa (3.6 psi)	at idle
Pressure	Fuel pressure at rated speed (all fuel injection pumps)	23	kPa (3.3 psi)	at rated speed; maximum 75 kPa (10.9 psi)
Pressure	Fuel pump pressure (crank)	1-2	psi	cranking engine over several times
Pressure	Fuel pump pressure (running)	2-3	psi	gauge held 16 inches above fuel pump
Pressure	Low oil pressure while cranking	8-10	lbs	2.7 AJ RV with LOPKO
Pressure	Normal oil pressure	25 or higher	psi	engine at operating temperature
Pressure	Normal oil pressure at operating temperature	20	PSI	2.7 AJ RV
Pressure	Oil by-pass valve opening	about 25	psi
Pressure	Pressure cap rating	15 (103.5)	psi (kPa)
Pressure	Pressure to open engine oil filter bypass valve (replaceable element)	130 to 170	kPa (19 to 25 psi)
Pressure	Pressure to open engine oil filter bypass valve (spin-on oil filter)	80 to 120	kPa (12 to 18 psi)
Resistance	Brushless exciter field leads resistance	12.2 + 10%	ohms	at 20 C (68 F.)
Resistance	Brushless exciter rotor lead pairs T1-T2, T2-T3, T1-T3	0.5 to 0.6	ohms	at 20 C (68 F.)
Resistance	Commutating reactor CMR21 any terminal to reactor frame	infinity
Resistance	Commutating reactor CMR21 between 1-2 and 3-4	0.4	ohms
Resistance	Commutating reactor CMR21 between 1-3, 2-3, 1-4, or 2-4	infinity

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	Ambient	Capacity	Notes
Coolant	Commercial heavy-duty coolant/antifreeze	ASTM D4985			Do not use coolant/antifreeze that only meets ASTM D3306. Perkins recommends 1:1 water/glycol, may be increased to 1:2 water to glycol
Coolant	Ethylene glycol base anti-freeze mixed with water				Do NOT use straight 100% ethylene glycol. Normal mixture approximately 50% anti-freeze and 50% water; ratio varies with ambient temperature.
Coolant	Perkins Extended Life Coolant (ELC) 1:1 water/glycol (premixed)	Perkins ELC; freeze protection to -36 °C (-33 °F)			ELC Concentrate lowers freezing point to -51 °C (-60 °F) for arctic conditions
Coolant	Perkins Liquid SCA + water	6 to 8 percent concentration of SCA			Part number 21825755; for stationary and marine applications without anti-boil or freeze protection
Coolant	ethylene glycol anti-freeze	minimum 50-50 mix of ethylene glycol anti-freeze and water			Complete change every year; use anti-freeze even when freezing temperatures are not expected
Coolant	50 Percent Ethylene Glycol	ASTM D4985	above -36°C	50.0 Percent	Freeze protection -36 °C (-33 °F), boil protection 106 °C (223 °F); 60 percent gives -51 °C (-60 °F) / 111 °C (232 °F)
Coolant	50 Percent Propylene Glycol	ASTM D4985	above -29°C	50.0 Percent	Do not use propylene glycol in concentrations that exceed 50 percent because of reduced heat transfer capability
Engine oil	SAE 10W-30				RM92-8M0086220U6 / RM92-8M0086221U3
Engine oil	SAE 15W-40				RM92-8M0096794U3; diesel engines
Engine oil	SAE 25W-40				RM92-8M0086227U3 / RM92-8M0086224U3
Engine oil	TC-W3	TC-W3			2-cycle outboard oil; RM92-858026QB1U6 / RM92-858027QB1U3 / RM92-858037QB1U3
Engine oil	medium grade engine oil				Add 3 to 5 drops to distributor oiler at regular intervals; crankcase oil change referenced in Oil System maintenance
Engine oil	SAE 0W20	EMA LRG-1 / API CH-4	-40°C to 10°C
Engine oil	SAE 0W30	EMA LRG-1 / API CH-4	-40°C to 30°C
Engine oil	SAE 0W40	EMA LRG-1 / API CH-4	-40°C to 40°C
Engine oil	SAE 5W30	EMA LRG-1 / API CH-4	-30°C to 30°C
Engine oil	SAE 5W40	EMA LRG-1 / API CH-4	-30°C to 40°C
Engine oil	SAE 10W30	EMA LRG-1 / API CH-4	-20°C to 40°C
Engine oil	SAE 15W40	EMA LRG-1 / API CH-4	-10°C to 50°C		Preferred oils: EMA DHD-1 multigrade, API CH-4 multigrade, ACEA E3. Minimum TBN of new oil = 10 times fuel sulfur level, minimum 5.
Fuel	ASTM 2-D or 1-D diesel fuel	Cetane number 45			Use Number 1-D diesel fuel when ambient temperatures are below 32 F (0 C) or during long periods of light load/cyclic operation.
Fuel	Diesel - Group 1 (preferred) DERV to EN590, Gas oil to BS2869 Class A2, ASTM D975-91 Class 2D, JIS K2204 (1992) Grades 1,2,3 and Special Grade 3	Cetane number 45 minimum; Viscosity 2.0 to 4.5 cSt at 40 °C; Density 0.835 to 0.855 Kg/liter; Sulfur 0.2% of mass maximum; Distillation 85% at 350 °C; Lubricity 460 micrometers maximum wear scar on ISO 12156-1			Group 2 (permissible) and Group 3 (aviation kerosene) also listed. Biofuel: a 5% mix of RME to EN14214 in conventional fuel is permitted. Water emulsion fuels are not permitted.
Fuel	clean, fresh, unleaded gasoline				Regular leaded gasoline may be used; do not use highly leaded premium fuels. Gaseous fuels optional with appropriate carburetor.
Gear oil	SAE 80W90				LUB11564U12 / LUB11565 / LUB11540U12 / LUB11552U12 / LUB11546
Gear oil	SAE 90W				RM92-858064QB1U6 / RM92-858065QB1U2
Grease	Lithium grease with Teflon				LUB11363
Grease	Marine grease				LUB11400 / LUB11406
Other	Power Trim & Tilt fluid				LUB11591U12 / LUB11592 / LUB11593

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

Procedures

Adjust anti-dieseling solenoid adjustment

With set stopped, turn lever counterclockwise; set screw so plates are closed but not binding.
Check lever has approximately 30 degrees travel counterclockwise from vertical.
Start set; lever should rotate approximately 60 degrees clockwise from stopped position.
Check solenoid plunger is fully seated.
If not, adjust distance between plunger and lever arm; repeat steps.

Battery Charge Rate Adjustment adjustment

⚠ Avoid overcharging.

Set slide tap on adjustable resistor R21 in generator air outlet to give about 2 amperes charging rate.
If charge winding AC output is below 19 volts on 12 volt battery charge models, 38 volts on 24 volt models, 50 volts on 32 volt models, test charging circuit for opens or grounds.
If a separate automatic demand control is used, adjust charge rate for maximum 4.5 amperes.

Carburetor adjustment for 6.5 NH RV adjustment

Turn idle mixture screw out 3/4 to 1 turn from seated.
Turn main mixture screw 1-1/2 to 1-3/4 turns out from seated.
Start set; adjust governor spring for 1860 RPM no load (62 Hz or 130 volts).
Hold governor arm so throttle lever rests on stop; adjust idle stop screw to 1500 RPM (50 Hz or 100 volts); release.
Adjust idle mixture screw to highest RPM or voltage; readjust governor spring to 1860 RPM no load.
Apply full load; adjust main mixture screw to highest RPM or voltage; readjust governor spring to 1770 RPM full load.
Remove and add load several times to check hunting; readjust governor spring if required.

Carburetor adjustment with load adjustment

⚠ Forcing the needle against its seat will bend the needle. The needle does not shut off fuel completely when turned all the way in.

Ensure ignition system works properly and governor is adjusted; allow engine to warm up.
With no engine load, turn idle adjustment out until speed drops slightly below normal, then in until speed returns.
Apply full load to engine.
Turn main adjustment in until speed drops slightly below normal, then out until speed returns to normal.

Engine Valve Lash - Inspect/Adjust (1104 engine) adjustment

⚠ To prevent possible injury, do not use the starter to turn the flywheel.

⚠ Hot engine components can cause burns.

Tools: feeler gauge

Remove the valve mechanism cover.
Rotate crankshaft clockwise; when No. 4 inlet opened and No. 4 exhaust not closed, measure No. 1 valves.
Loosen the valve adjustment screw locknut on adjustment screw.
Place the appropriate feeler gauge between the rocker arm and valve.
Turn the adjustment screw until correct valve lash is achieved.
Tighten the locknut while holding the adjustment screw from turning.
Repeat for No. 3, No. 4 and No. 2 cylinders per engine sequence.
Install the valve mechanism cover.

Finding Top Center Position for No. 1 Piston adjustment

Tools: 27610211 Crankshaft timing pin, 27610212 Camshaft timing pin

Remove the valve mechanism cover, glow plugs, and the cover for the front housing.
Rotate crankshaft until No. 4 inlet valve has just opened and No. 4 exhaust valve has not completely closed.
Carefully rotate crankshaft to align hole in crankshaft with hole in cylinder block and timing case.
Insert the 27610211 Crankshaft Timing Pin fully into the hole in the crankshaft web.
Insert the 27610212 Camshaft Timing Pin through the camshaft gear into the timing case body.
The engine is now set at the top center position for No. 1 piston.
Remove the timing pins from the camshaft gear and the crankshaft web.

Ignition timing - engine stopped (MJB) adjustment

Tools: Continuity test lamp, Battery, Feeler gauge

Remove breaker box cover; disconnect lead to ignition points and install continuity test lamp and battery.
Rotate flywheel clockwise until TC mark on flywheel approaches timing indicator.
Slowly rotate flywheel clockwise until light goes out; this is the ignition point (5 ATC).
If timing is incorrect, align 5 ATC mark and timing pointer; loosen breaker plate capscrews and rotate plate so light goes out.
Tighten plate and recheck timing.

Valve clearance adjustment MJB adjustment

Tools: Feeler gauge, Wrench

Turn flywheel so piston of valve to be checked is 10 to 45 degrees after TDC of compression stroke.
Turn flywheel until TC mark lines up with timing pointer, then an additional 10 to 45 degrees clockwise.
Check cylinder head bolt torque.
Using a feeler gauge, check clearance between rocker arm and valve.
Adjust with the locknut securing rocker arm to cylinder head until proper gap is established.

Valve clearance adjustment MJC/RJC adjustment

Tools: Feeler gauge, Wrench

Adjust valve clearance in firing order 1-2-4-3 sequence.
Set timing for number 1 cylinder and adjust its valve clearance.
Turn flywheel 180 degrees clockwise for number 2 cylinder; adjust clearance.
Turn flywheel 180 degrees clockwise for number 4 cylinder; adjust clearance.
Turn flywheel 180 degrees clockwise for number 3 cylinder; adjust clearance.

Voltage Calibration Adjustment adjustment

Tools: AC voltmeter

If set has a voltage adjust potentiometer (R22) on the meter panel, set pointer halfway between minimum and maximum positions.
With unit running at no load, turn generator voltage potentiometer R26 on VR21 clockwise to increase output voltage; turn R26 counterclockwise to decrease output voltage.

Voltage Stability Adjustment adjustment

With generator set running at no load, turn potentiometer R27 to a position where voltage tends to be unstable or hunt.
Turn R27 clockwise slowly until voltage first stabilizes.

Battery Checkout diagnostic

Tools: hydrometer

Check charge condition of battery with a hydrometer.
Specific gravity should be between 1.290 and 1.225 when 75 percent charged. If not, recharge the battery.
Check electrolyte level. Add approved water to keep electrolyte at its proper level.
If battery will not recharge, replace it. Keep battery connections tight and clean.

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
110	1	518	V1	50 hertz
110/190	3	53C	V1	50 hertz
110/220	1	518	V1	50 hertz
110/220	1	53C	V1	50 hertz
110/220	3	518	V1	50 hertz
115	1	518	V2	50 hertz
115/200	3	53C	V2	50 hertz
115/230	1	518	V2	50 hertz
115/230	1	53C	V2	50 hertz
115/230	3	518	V2	50 hertz
120	1	3C	V1	60 hertz
120	1	518	V3	50 hertz
120/208	3	3C	V1	60 hertz
120/208	3	53C	V3	50 hertz
120/240	1	3C	V1	60 hertz. Connect X1 to VR21-5 for 50 hertz and X1 to VR21-6 for 60 hertz generators. Jumper W10 on VR21 must connect VR21-V4 to V1, V2, or V3 as listed.
120/240	1	518	V3	50 hertz
120/240	1	53C	V3	50 hertz
120/240	3	3C	V1	60 hertz
127/220	3	3C	V2	60 hertz
127/220	3	53C	V4	50 hertz
139/240	3	3C	V4	60 hertz
220/380	3	518	V1	50 hertz
230/400	3	518	V2	50 hertz
240/416	3	3C	V1	60 hertz; Figure 6 text partly garbled
240/416	3	518	V3	50 hertz
254/440	3	3C	V2	60 hertz
254/440	3	518	V4	50 hertz
277/480	3	3C	V4	60 hertz
347/600	3	9X	V4	60 hertz; code 9X 3-phase 347/600 volt generators have four output leads

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

Common questions

What is the oil capacity of the Cummins/Onan J Series?

The Cummins/Onan J Series engine has an oil capacity of 6.15 liters.

How often should you change the oil in the Cummins/Onan J Series?

The Cummins/Onan J Series oil change interval is every 500 hours.

What is a common problem with the Cummins/Onan J Series engine?

A commonly reported issue on generators using the Cummins/Onan J Series is: Engine runs, shuts down and LOW OIL PRESSURE Lamp lights. Cause: Possible fuel or ignition system problem: empty fuel tank, fuel or leaks, or plugged fuel lines. Fix: Check for empty fuel tank, fuel or leaks, or plugged fuel lines and correct as required.