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Cummins/Onan GH280 Engine

The Cummins/Onan GH280 is an engine rated at 3600 rpm. It powers generator sets from Cummins/Onan, including the 3.5 EGHEM, 4.0 EGHAB and 4.0 EGHEB. It holds 0.9 L (0.2 gal) of oil.

Also known as: Onan GH280

3600 rpm

Rated speed

0.9 L

Oil capacity

On this pageSpecs Generator sets FAQ Service intervals Torque & specs Fluids Procedures

Engine specifications

Oil capacity	0.9 L
Rated speed	3600 rpm

Generator sets powered by this engine

Cummins/Onan 3.5 EGHEMCummins/Onan 4.0 EGHABCummins/Onan 4.0 EGHEB

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

Troubleshooting

Symptoms & remedies

Symptom	Cause	Remedy
Engine Misfires	Faulty ignition due to: a. worn or fouled spark plug; b. faulty ignition system; c. faulty plug wire; Lean fuel mixture due to: a. incorrectly adjusted carburetor; b. incorrect float level; c. dirt in carburetor; d. vacuum leak; Contaminated fuel; Dirty air cleaner	A. Clean or replace spark plug. b. See Ignition System section. c. Check spark plug wire and replace if necessary. a. See Carburetor Adjustment section. b. Check carburetor float. c. Disassemble carburetor and clean all internal passages. d. Drain fuel tank and refill with fresh fuel. e. Clean or replace air cleaner.
Engine Backfires	Faulty ignition due to: a. worn or fouled spark plug; b. faulty ignition system; Lean fuel mixture due to: a. incorrectly adjusted carburetor; b. incorrect float level; c. dirt in carburetor; d. vacuum leak;	A. Clean or replace spark plug. b. See Ignition System section. c. Check spark plug wire and replace if necessary. a. See Carburetor Adjustment section. b. Check carburetor float. c. Disassemble carburetor and clean all internal passages.
Engine Lacks Power	Faulty ignition due to: a. worn or fouled spark plug; b. faulty ignition system; Dirty air cleaner; Restricted fuel flow due to plugged fuel filter; Incorrect fuel mixture due to: a. incorrectly adjusted carburetor; b. incorrect float level; c. dirt in carburetor; Lean fuel mixture due to: a. incorrectly adjusted carburetor; b. incorrect float level; c. dirt in carburetor; d. vacuum leak; Exhaust system blocked or restricted; Incorrect valve clearance; No load speed set too low; Excessive engine wear or damage to engine; Choke valve blockage or choke lever set incorrectly;	A. Clean or replace spark plug. b. See Ignition System section. c. Clean or replace air cleaner. d. Clean or replace fuel filter. e. a. See Carburetor Adjustment section. b. Check carburetor float. c. Disassemble carburetor and clean all internal passages. f. Locate and remove cause of blockage. g. Adjust valve clearance/inspect valves (see Engine Block Assembly section). h. Adjust governor setting. i. See Engine Block Assembly section. j. Open choke lever fully, if problem continues see fuel System section.
Engine Overheats	Restricted air flow due to dirt or debris blocking air inlet or outlet; Dirt or oil covering engine cooling fins; Cooling fan plugged or broken; Lean fuel mixture due to: a. incorrectly adjusted carburetor; b. incorrect float level; c. dirt in carburetor;	A. Clear away any debris that may restrict airflow. b. Clean away all dirt and oil from engine cooling fins. c. Inspect cooling fan, see Generator Service section. d. a. See Carburetor Adjustment section. b. Check carburetor float. c. Disassemble carburetor and clean all internal passages.
Black Exhaust Smoke	Rich fuel mixture due to: a. dirty air cleaner; b. choke closed; c. incorrectly adjusted carburetor; d. dirt in the carburetor; Lean fuel mixture due to: a. dirty air cleaner; b. incorrect float level; c. incorrectly adjusted carburetor; d. dirt in the carburetor; Clogged or faulty breather; Contaminated fuel; Excessive engine wear;	A. Clean or replace air cleaner. b. Check choke setting. c. See Carburetor Adjustment section. d. Disassemble carburetor and clean all internal passages. a. Clean or replace air cleaner. b. Check carburetor float. c. See Carburetor Adjustme
White or Blue Exhaust Smoke	Clogged or faulty breather; Contaminated fuel;	A. Clean or replace air cleaner. b. Check choke setting. c. See Carburetor Adjustment section. d. Disassemble carburetor and clean all internal passages.
Engine Hunts or Surges	Sticking or binding governor linkage; Incorrect governor adjustment; Faulty governor spring; Incorrect fuel mixture due to: a. incorrectly adjusted carburetor; b. incorrect float level; c. dirt in carburetor; Governor mechanism worn excessively; Fuel supply problem caused by: a. Dirty fuel filter; b. Contaminated fuel supply;	A. Clean or replace air cleaner. b. Check choke setting. c. See Carburetor Adjustment section. d. Disassemble carburetor and clean all internal passages. e. Adjust valve clearance/inspect valves (see Engine Block Assembly section). f. Adjust governor setting. g. See Engine Block Assembly section. h. Open choke lever fully, if problem continues see fuel System section.

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

Common problems

White or blue exhaust smoke
Cause: Dirty air cleaner
Fix: Clean or replace air cleaner
UNIT RUNS THEN SURGES
Cause: 1. Loose or worn spark plug lead 2. Faulty spark plug. 3. Dirty fuel filter or generator set at too steep of an angle. 4. Governor out of adjustment or lean fuel mixture.
Fix: 1. Check spark plug lead connection. 2. Remove and clean or replace. 3. Check fuel filter and angle of generator set. 4. Contact an Onan service center.
UNIT RUNS THEN STOPS
Fix: Add fuel. Add oil. Reduce oil level.
Restricted fuel flow
Cause: Plugged fuel filter
Fix: Clean or replace fuel filter
Restricted air flow
Cause: Dirt or debris blocking air inlet or outlet
Fix: Clear away any debris that may restrict airflow
No load speed set too low
Fix: Adjust governor setting
NO DC OUTPUT VOLTAGE
Cause: 1. Open DC circuit breaker due to an overload.
Fix: 1. Remove all loads, reset breaker, check for shorted battery or load defects. Do not exceed rated load specifications.
NO AC OUTPUT VOLTAGE
Cause: Open AC circuit breaker due to an overload
Fix: Remove all loads, re-set circuit breaker, check tools or appliances being used for defects. Do not exceed generator set rated load specifications.
Lean fuel mixture
Cause: Incorrectly adjusted carburetor
Fix: See Carburetor Adjustment section
Incorrect valve clearance or defective valve(s)
Fix: E140H engine: See Onan Elite Horizontal engine manual 965-0758 GH170, GH280 engines: See Engine Block Assembly section
Incorrect fuel mixture
Cause: Incorrectly adjusted carburetor
Fix: See Carburetor Adjustment section
FAILS TO CRANK
Cause: 1. Low battery. 2. Bad battery connection.
Fix: 1. Check battery electrolyte level. 2. Clean and tighten all battery and cable connections.
EXHAUSTING BLACK SMOKE
Cause: Open DC circuit breaker due to an overload
Fix: Remove all loads, reset circuit breaker, check for an overload or short circuit. Do not exceed generator set rated load specifications.
Exhaust system blocked or restricted
Fix: Locate and remove cause of blockage
Excessive engine wear or damage to engine
Fix: E140H engine: See Onan Elite Horizontal engine manual 965-0758 GH170, GH280 engines: See Engine Block Assembly section

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan GH280.

Service intervals

Item	Action	Hours	Months	Notes
Engine Oil and Filter (if so equipped)	Change			First service — 2,3,4 - Perform after first 24 hours of operation on new sets. Perform more often in extremely dusty conditions. Perform more often when operating in hot conditions.
Valve Lash Clearance	Adjust			First service — 2,6 - Perform after first 24 hours of operation on new sets. Must be performed by a qualified mechanic.

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 element mounting nut - tighten after seating on cover	1-1/2	turns
Clearance	Cylinder head surface flatness	0.05 mm (0.0020)	mm
Clearance	Oil filter canister - tighten after gasket contacts mounting pad	1/2 to 3/4	turn
Clearance	Valve seat width	1.00 to 1.30 mm (0.039 to 0.051 in)	mm
Gap	Magneto coil to rotor magnet clearance	0.25 to 0.40 mm (0.010 to 0.016 in)	mm
Gap	Spark plug gap	0.028	in. (0.7 mm)
Gap	Spark plug gap	0.035	in. (0.89 mm)
Gap	Spark plug gap	0.7 mm (0.028 in)	mm
Gap	Spark plug gap	0.89 mm (0.035 in)	mm
Gap	Spark plug gap (allowable)	0.89 to 1.02 mm (0.035 to 0.040 in)	mm
Gap	Transistor magnet unit to flywheel magnet clearance	0.4 to 0.6 mm (0.0157 to 0.0236 in)	mm
Other	Battery electrolyte specific gravity - charge if below 1.215; stop charging at 1.260	1.260	specific gravity	at approximately 80 F (27 C)
Other	Brush height minimum	0.136 in (3.5 mm)	in
Other	Capacitor value	approximately 13 mfd	mfd
Other	Ignition timing (BTDC) (fixed)	21	degrees
Other	Ignition timing (BTDC) (fixed)	23	degrees
Other	Ignition timing (BTDC) (fixed)	25	degrees
Pressure	Compression pressure	196 kPa (28 psi)	kPa
Resistance	Ignition primary coil resistance	0.5 to 1.3 ohms	ohms
Resistance	Ignition secondary coil resistance	9k to 13 kohms	kohms
Resistance	Rotor coil 4 kW - 60 Hz	47 Ω	ohms
Resistance	Rotor coil 5 kW - 60 Hz	55 Ω	ohms
Resistance	Rotor coil 6 kW - 60 Hz	65 Ω	ohms
Resistance	Stator DC coil 4 kW - 60 Hz	0.6 - 1.0 Ω	ohms
Resistance	Stator main coil 4 kW - 60 Hz	0.7 - 1.0 Ω	ohms
Resistance	Stator resistance 20 amp system	0.27 to 0.33 Ohms	ohms
Resistance	Stator resistance 5 amp system	0.54 to 0.66 Ohms	ohms
Resistance	Stator sub coil 4 kW - 60 Hz	1.2 - 1.6 Ω	ohms
Speed	No-load frequency 50 Hz models	53 ± 0.5 Hz (3150-3180 rpm)	Hz	no load, warm
Speed	No-load frequency 60 Hz models	63 ± 0.5 Hz (3750-3780 rpm)	Hz	no load, warm
Torque	Adapter bracket to engine	13 to 15.9 ft-lb (17.7 to 21.6 N·m)	ft-lb
Torque	Alternator stator screws M6 x 25	10-15 N·m (7-11 lb-ft)	N·m
Torque	Connecting rod bolts M8 x 44	24-27 N·m (18-20 lb-ft)	N·m
Torque	Connecting rod screws	10.1 to 14.5 ft-lb (13.7 to 19.6 N·m)	ft-lb
Torque	Connecting rod screws	17.4 to 21.7 ft-lb (23.5 to 29.4 N·m)	ft-lb
Torque	Crankcase screws	10.1 to 14.5 ft-lb (13.7 to 19.6 N·m)	ft-lb
Torque	Cylinder head No. 6 flange bolt M8 x 50	16-22 N·m (12-16 lb-ft)	N·m
Torque	Cylinder head bolts No. 1-5	42-50 N·m (31-37 lb-ft)	N·m
Torque	Cylinder head screws	15.9 to 20.3 ft-lb (21.6 to 27.5 N·m)	ft-lb
Torque	Cylinder head screws	18.1 to 23.9 ft-lb (24.5 to 32.4 N·m)	ft-lb
Torque	Flywheel mounting nut	43.4 to 50.6 ft-lb (58.8 to 68.6 N·m)	ft-lb
Torque	Flywheel mounting nut	47.0 to 54.2 ft-lb (63.7 to 73.5 N·m)	ft-lb
Torque	Flywheel nut M18	122-138 N·m (90-102 lb-ft)	N·m
Torque	Gearcase bolts	16-22 N·m (12-16 lb-ft)	N·m
Torque	Genset to frame vibration isolators	16 ft-lb (21.7 N·m)	ft-lb
Torque	Governor arm nut M6	8.1-10.9 N·m (6-8 lb-ft)	N·m
Torque	Governor lever screw	5.1 to 8.7 ft-lb (6.9 to 11.8 N·m)	ft-lb
Torque	Governor lever screw	8.0 to 14.5 ft-lb (10.8 to 19.6 N·m)	ft-lb
Torque	Ignition coil bolt M6 x 30	10-15 N·m (7-11 lb-ft)	N·m
Torque	Output terminal nut	1.4 to 1.8 ft-lb (1.9 to 2.45 N·m)	ft-lb
Torque	Rocker arm lock nut	5.8 to 9.4 ft-lb (7.8 to 12.7 N·m)	ft-lb
Torque	Rocker arm lock nut	8.0 to 12.3 ft-lb (10.8 to 16.7 N·m)	ft-lb
Torque	Rocker mounting nut	43.4 to 50.6 ft-lb (58.8 to 68.6 N·m)	ft-lb
Torque	Rocker mounting nut	47.0 to 54.2 ft-lb (63.7 to 73.6 N·m)	ft-lb
Torque	Rotor through-bolt	19 to 20 ft-lb (25.7 to 27.1 N·m)	ft-lb
Torque	Spark plug	20	lbs-ft (26 N-m)
Torque	Spark plug	7.2 to 18.1 ft-lb (9.8 to 24.5 N·m)	ft-lb
Torque	Spark plug M14-1.25	24-30 N·m (18-22 lb-ft)	N·m
Torque	Starter bolts M8 x 40	16-22 N·m (12-16 lb-ft)	N·m
Torque	Stator through-bolt	4.3 to 6.5 ft-lb (5.9 to 8.8 N·m)	ft-lb

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	Notes
Engine oil	SAE 5W-30	API Class SG or SH (also SG/CD, SG/CE, SH/CD or SH/CE)	-28°C to 10°C	-20 F to 50 F (-28 C to 10 C)
Engine oil	SAE 10W-30	API Class SG or SH (also SG/CD, SG/CE, SH/CD or SH/CE)	-18°C to 27°C	0 F to 80 F (-18 C to 27 C)
Engine oil	SAE 10W-40	API Class SG or SH (also SG/CD, SG/CE, SH/CD or SH/CE)	-18°C to 27°C	0 F to 80 F (-18 C to 27 C)
Engine oil	SAE 15W-40 (OnaMax)	API Class SG or SH (also SG/CD, SG/CE, SH/CD or SH/CE)	-12°C to 38°C	10 F to 100 F (-12 C to 38 C)
Engine oil	SAE 30	API Class SG or SH (also SG/CD, SG/CE, SH/CD or SH/CE)	above 0°C	32 F (0 C) and higher
Fuel	Unleaded gasoline with octane rating (anti-knock index) of 87 or higher			Do not use gasoline or gasoline additives (de-icers) containing methanol. Oxygenated gasolines acceptable.

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

Procedures

Valve Clearance Adjustment adjustment

Tools: feeler gauge, wrenches

Adjust only when engine is at ambient temperature.
Rotate engine until piston is at top dead center and both valves closed.
Check clearance between valve stem top and rocker arm with feeler gauge.
Loosen locking nut and turn adjusting nut to obtain correct clearance.
Tighten locking nut and recheck clearance.
Check rocker arm bolts have not loosened.

Starter Solenoid Test (GH280 Engine) diagnostic

⚠ Disconnect battery before servicing to prevent accidental starting.

Tools: jumper leads

Connect jumper lead between battery positive (+) terminal and solenoid S terminal.
Momentarily connect jumper between battery negative (-) and solenoid body.
Solenoid contacts should close; replace solenoid if it does not activate.

Air Cleaner Maintenance - 5.0 and 6.0 kW Gensets maintenance

⚠ Failure to adequately wring out excess oil may cause a drop in engine power due to restriction of inlet air.

Remove the outer cover by rotating the quarter-turn fastener counterclockwise to its vertical position; lift off the cover.
Remove and wash the foam wrapper in water and detergent; squeeze it dry like a sponge, rinse and allow to dry.
Coat the wrapper evenly with one tablespoon (14 grams) of SAE 30 engine oil; knead in and wring out excess oil.
Re-install the foam wrapper over the paper element by stretching it over the inner cover.
For element replacement, close the choke plate; remove the mounting nut, inner cover and element; wipe the base clean.
Install the new paper element and secure with the inner cover and nut; tighten the nut 1-1/2 turns after seating.

Battery Care maintenance

⚠ Ignition of explosive battery gases can cause severe personal injury. Do not smoke or allow any flame, spark or other ignition source near the battery.

⚠ Battery electrolyte can cause severe eye damage and skin burns. Wear goggles, rubber gloves and a protective apron.

Tools: Battery hydrometer, Battery puller tool

Keep the battery case clean and dry; wipe with a damp cloth when dirt accumulates.
Make certain the battery cable connections are clean and tight; use a battery puller tool to remove cables.
Identify cables as positive (+) or negative (-) before connecting. Connect the negative (-) cable last.
Apply a light coating of petroleum jelly or non-conductive grease to battery connections to retard corrosion.
Maintain the electrolyte level by adding distilled water as needed to reach the split-level marker.
Use a battery hydrometer to check specific gravity of each cell. Charge if below 1.215; stop charging at 1.260 at about 80 F (27 C).

Fuel Filter Replacement (4.0 kW and Below) maintenance

⚠ Fuel presents fire or explosion hazard; keep ABC extinguisher nearby.

Close fuel supply valve; run set until it runs out of fuel; let cool.
Remove fuel line from shutoff valve and collect fuel in a container.
Unscrew sediment bowl from fuel supply valve and clean it.
Remove screen and clean dirt and particulate off the screen.
Reinstall screen and sediment bowl; attach fuel line securely.

Fuel Filter Replacement - Gensets 4.0 kW And Below maintenance

⚠ Fuel presents the hazard of fire or explosion. Do not permit any flame, spark, pilot light, cigarette, or other ignition source near the fuel system.

Close the fuel supply valve and let the set run until it runs out of fuel; let it cool down.
Remove the fuel line from the fuel shutoff valve and collect the fuel in a suitable container.
Unscrew the sediment bowl from the fuel supply valve and clean it.
Remove the screen and clean any dirt and particulate off the screen.
Reinstall the screen and sediment bowl. Attach the fuel line securely to the fuel shutoff valve.

Muffler Disassembly maintenance

⚠ Exhaust gas hazard; do not operate with any exhaust leaks.

Tools: wrenches

Allow set to cool before servicing.
Remove heat shield covering exhaust pipe and engine.
Remove mounting nuts securing muffler flange to engine.
Remove screws securing muffler to support bracket and generator flange; remove exhaust gasket.
Install new exhaust gasket and muffler; tighten hardware to specified torque.

Muffler and Spark Arrester Service maintenance

⚠ A hot muffler can cause severe burns.

⚠ Most part cleaning solvents are flammable; work in a well ventilated area and keep an ABC fire extinguisher nearby.

Tools: Wire brush, Commercial solvent

Allow the generator set to cool down before servicing the muffler.
Inspect the muffler for corrosion and physical defects.
Operate the set and check for exhaust leaks and noisy operation; replace a noisy or defective muffler.
Remove the spark arrester screen and inspect for damage; replace if defective.
Clean by lightly tapping the screen and cleaning deposits with a wire brush; use commercial solvent if necessary.
Allow screen to dry, then reassemble and attach securely.

Oil and Filter Change maintenance

⚠ Accidental starting of the engine can result in severe personal injury or death. Disconnect the spark plug and battery negative cable before changing oil.

⚠ Crankcase pressure can blow hot engine oil out the fill opening causing severe burns. Stop the genset before removing the oil fill cap.

⚠ Contact with used engine oil can cause cancer or reproductive toxicity.

Run the engine until warm. Stop it and disconnect the spark plug and, if equipped, the battery negative (-) cable. Make sure the set is level.
Remove the oil fill cap.
Place a pan under the oil drain opening and remove the oil drain plug. (5.0 kW and above: spin off the oil filter canister.)
Reinstall the drain plug securely after the oil has drained completely.
Wipe the filter mounting surface; be sure the gasket is in place and coat it with a thin film of oil.
Spin on the new filter by hand until the gasket touches the pad, then turn an additional 1/2 to 3/4 turn. Do not overtighten.
Refill with API Class SG or SH oil of the correct viscosity; see Specifications for oil capacity.
Reconnect the spark plug and battery. Start the engine and check for oil leaks around the drain plug and filter.

Preparing Generator Set For Storage maintenance

⚠ Hot oil can cause severe burns.

⚠ Battery electrolyte can cause severe eye damage and burns to the skin.

⚠ Batteries present the hazard of explosion.

Add a fuel preservative and stabilizer such as OnaFresh to the fuel supply; run at 50 percent load for 30 minutes.
Disconnect the load; turn the fuel supply valve off and remove the air filter.
As the set runs out of fuel, squirt fogger such as OnaGard into the carburetor intake, then reassemble the air filter.
When the set stops, remove the spark plug and squirt one tablespoon (about 30 ml) clean engine oil into the spark plug hole; turn the engine over several revolutions; replace the plug.
Drain the oil base while still warm; refill the crankcase and attach a tag indicating oil viscosity used.
Electric start models: disconnect battery negative (-) cable first; store battery in a cool dry place and connect to a charger every 30 days.
Cover the generator set and store in a dry protected area.

Spark Plug Maintenance and Replacement maintenance

⚠ Shut the fuel valve and handle the fuel tank carefully to prevent fuel leakage when raising the fuel tank.

Tools: Wire brush, Wrench, Torque wrench

Remove the spark plug and clean carbon and other deposits off with a wire brush.
Inspect and measure the plug gap. Replace the plug if it is discolored or badly fouled.
Thread the spark plug in by hand until it seats to prevent cross-threading.
If reusing the spark plug, turn it with a wrench an additional 1/4 turn.
If the spark plug is new, turn it an additional 3/8 to 1/2 turn; or torque to 20 lbs-ft (26 N-m).
If needed, the fuel tank can be raised for easier service access after reducing fuel level and closing the fuel shutoff valve.

Adding AC Loads operation

⚠ Continuous overloading can cause high operating temperatures that could damage the set. Keep the load within the nameplate rating.

⚠ Electrical shock can cause severe personal injury or death. Cord and plug equipment must have a ground terminal.

Note the rated output of the generator set from the nameplate or Specifications section.
Check the load rating of each load; total wattage must not exceed the genset rated output.
If a motor load and another load are close to rated output, start the motor load first and let it reach normal speed.
Connect the AC loads to the receptacle(s) on the control panel.
Make sure the cord and plug connector have ground terminals.

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 GH280?

The Cummins/Onan GH280 engine has an oil capacity of 0.9 liters.

Which generators use the Cummins/Onan GH280 engine?

The Cummins/Onan GH280 powers 3 generator set(s), including Cummins/Onan 3.5 EGHEM, Cummins/Onan 4.0 EGHAB, Cummins/Onan 4.0 EGHEB.

What is a common problem with the Cummins/Onan GH280 engine?

A commonly reported issue on generators using the Cummins/Onan GH280 is: White or blue exhaust smoke. Cause: Dirty air cleaner. Fix: Clean or replace air cleaner.