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
| Oil capacity | 0.9 L |
|---|---|
| Rated speed | 3600 rpm |
How to read your Cummins/Onan engine serial & model number →
| 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.
Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan GH280.
Step-by-step procedures compiled from the Cummins/Onan service manual for this engine.
| Type | Item | Value | Unit | Condition |
|---|---|---|---|---|
| Clearance | Cylinder head surface flatness | 0.05 mm (0.0020) | mm | |
| 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 | 0.7 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 | Brush height minimum | 0.136 in (3.5 mm) | in | |
| Other | Capacitor value | approximately 13 mfd | mfd | |
| 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 | 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 | |
| Torque | Valve lash adjusting nut M7 | 7-11 N·m (5-8 lb-ft) | N·m | |
| Valve clearance | Valve clearance intake and exhaust | 0.05 to 0.10 mm (0.0020 to 0.0039 in) | mm | ambient temperature |
| Valve clearance | Valve lash intake and exhaust | 0.15 to 0.25 mm (0.006 to 0.010 in) | mm | ambient temperature |
| Voltage | Battery voltage | 12 to 13 VDC | VDC | engine not running |
| Voltage | Stator output | 29 VAC @ 1800 RPM; 57 VAC @ 3600 RPM | VAC | |
| Voltage | Voltage regulator output | 13.6 to 14.7 VDC | VDC | any speed within operating range |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Tools: feeler gauge, wrenches
⚠ Disconnect battery before servicing to prevent accidental starting.
Tools: jumper leads
⚠ Fuel presents fire or explosion hazard; keep ABC extinguisher nearby.
⚠ Exhaust gas hazard; do not operate with any exhaust leaks.
Tools: wrenches
⚠ Close fuel valve and drain float chamber; no flame or spark near fuel system.
Tools: wrenches
⚠ Moving parts can cause severe personal injury; use protective equipment.
⚠ Spiral spring is under tension; wear protective eye wear, gloves, clothing.
Tools: gear puller, press
Tools: strap wrench, torque wrench
Tools: lead hammer
Tools: torque wrench, screwdriver
⚠ On AVR models the brush block assembly will be damaged if not removed.
Tools: screwdriver, wrenches
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
The Cummins/Onan GH280 engine has an oil capacity of 0.9 liters.
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.
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.