Cummins/Onan 5.0 EGPAD troubleshooting: 121 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 5.0 EGPAD — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| Engine misfires | Faulty ignition due to worn or fouled spark plug | Clean or replace spark plug. |
| Engine misfires | Faulty ignition due to faulty ignition system | See Ignition System section. |
| Engine misfires | Faulty ignition due to faulty plug wire | Check spark plug wire and replace if necessary. |
| Engine misfires | Lean fuel mixture due to incorrectly adjusted carburetor | See Carburetor Adjustment section. |
| Engine misfires | Lean fuel mixture due to incorrect float level | Check carburetor float. |
| Engine misfires | Lean fuel mixture due to dirt in carburetor | Disassemble carburetor and clean all passages. |
| Engine misfires | Lean fuel mixture due to vacuum leak | Locate leak, check for loose carburetor. |
| Engine misfires | Contaminated fuel | Drain fuel tank and refill with fresh fuel. |
| Engine misfires | Dirty air cleaner | Clean or replace air cleaner. |
| Engine backfires | Faulty ignition due to worn or fouled spark plug | Clean or replace spark plug. |
| Engine backfires | Faulty ignition due to faulty ignition system | See Ignition System section. |
| Engine backfires | Lean fuel mixture due to incorrectly adjusted carburetor | See Carburetor Adjustment section. |
| Engine backfires | Lean fuel mixture due to incorrect float level | Check carburetor float. |
| Engine backfires | Lean fuel mixture due to dirt in carburetor | Disassemble carburetor and clean all passages. |
| Engine backfires | Lean fuel mixture due to vacuum leak | Locate leak, check for loose carburetor. |
| Engine backfires | Excessive engine wear | E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Engine lacks power | Faulty ignition due to worn or fouled spark plug | Clean or replace spark plug. |
| Engine lacks power | Faulty ignition due to faulty ignition system | See Ignition System section. |
| Engine lacks power | Dirty air cleaner | Clean or replace air cleaner. |
| Engine lacks power | Restricted fuel flow due to plugged | Clean or replace fuel filter. |
| Engine lacks power | Incorrect fuel mixture due to incorrectly adjusted carburetor | See Carburetor Adjustment section. |
| Engine lacks power | Incorrect fuel mixture due to incorrect float level | Check carburetor float. |
| Engine lacks power | Incorrect fuel mixture due to dirt in carburetor | Disassemble carburetor and clean all internal passages. |
| Engine lacks power | Exhaust system blocked or restricted | Locate and remove cause of blockage. |
| Engine lacks power | Incorrect valve clearance or defective valve(s) | Adjust valve clearance/inspect valves; E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Engine lacks power | No load speed set too low | Adjust governor setting. |
| Engine lacks power | Excessive engine wear or damage to engine | E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Engine lacks power | Choke valve blockage or choke lever set incorrectly | 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 | Clear away any debris that may restrict airflow. |
| Engine overheats | Dirt or oil covering engine cooling fins | Clean away all dirt and oil from engine cooling fins. |
| Engine overheats | Cooling fan plugged or broken | Inspect cooling fan, see Generator Service section. |
| Engine overheats | Lean fuel mixture due to incorrectly adjusted carburetor | See Carburetor Adjustment section. |
| Engine overheats | Lean fuel mixture due to incorrect float level | Check carburetor float. |
| Engine overheats | Lean fuel mixture due to dirt in carburetor | Disassemble carburetor and clean all internal passages. |
| Black exhaust smoke | Rich fuel mixture due to dirty air cleaner | Clean or replace air cleaner. |
| Black exhaust smoke | Rich fuel mixture due to choke closed | Check choke setting. |
| Black exhaust smoke | Rich fuel mixture due to incorrectly adjusted carburetor | See Carburetor Adjustment section. |
| Black exhaust smoke | Rich fuel mixture due to dirt in the carburetor | Disassemble carburetor and clean all internal passages. |
| White or blue exhaust smoke | Lean fuel mixture due to dirty air cleaner | Clean or replace air cleaner. |
| White or blue exhaust smoke | Lean fuel mixture due to incorrect float level | Check carburetor float. |
| White or blue exhaust smoke | Lean fuel mixture due to incorrectly adjusted carburetor | See Carburetor Adjustment section. |
| White or blue exhaust smoke | Lean fuel mixture due to dirt in the carburetor | Disassemble carburetor and clean all internal passages. |
| White or blue exhaust smoke | Clogged or faulty breather | Clean or replace breather. |
| White or blue exhaust smoke | Contaminated fuel | Drain and replace fuel. |
| White or blue exhaust smoke | Excessive engine wear | E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Engine hunts or surges | Sticking or binding governor linkage | Check linkage alignment and straighten or replace. Clean governor linkage. |
| Engine hunts or surges | Incorrect governor adjustment | See Governor section. Also: E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Engine hunts or surges | Faulty governor spring | Replace governor spring. |
| Engine hunts or surges | Incorrect fuel mixture due to incorrectly adjusted carburetor | See Carburetor Adjustment section. |
| Engine hunts or surges | Incorrect fuel mixture due to incorrect float level | Check carburetor float. |
| Engine hunts or surges | Incorrect fuel mixture due to dirt in carburetor | Disassemble carburetor and clean all internal passages. |
| Engine hunts or surges | Governor mechanism worn excessively | E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Engine hunts or surges | Fuel supply problem caused by dirty fuel filter | Clean or replace fuel filter. |
| Engine hunts or surges | Fuel supply problem caused by contaminated fuel supply | Drain and refill fuel supply. |
| Uses too much oil (Note: New engines sometimes use excess oil during break-in) | Oil viscosity is too light or oil is diluted | Drain oil and refill with correct viscosity oil. |
| Uses too much oil (Note: New engines sometimes use excess oil during break-in) | Crankcase breather valve is dirty or defective | Clean crankcase breather or replace if defective. |
| Uses too much oil (Note: New engines sometimes use excess oil during break-in) | Oil leaks | Locate source of leak and repair as required. |
| Uses too much oil (Note: New engines sometimes use excess oil during break-in) | Excessive engine wear | E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Uses too much oil (Note: New engines sometimes use excess oil during break-in) | Light loading | Do not run set at no load for long periods of time. |
| Engine shuts down and will not restart | Low oil level | Add oil as required. |
| Engine shuts down and will not restart | Low oil level switch defective | Replace oil level switch. E140H engine: See Onan Elite Horizontal engine manual 965-0758; GH170, GH280 engines: See Engine Block Assembly section |
| Engine shuts down and will not restart | Fouled spark plug | Clean or replace spark plug. |
| Engine shuts down and will not restart | Faulty fuel system | See Fuel System section. |
| Engine does not crank (electric start models only) | Defective Start/On/Stop switch | Check switch for continuity and replace if defective. |
| Engine does not crank (electric start models only) | Open circuit in wiring between Start/On/Stop switch and starter solenoid or between battery and starter | Check wiring and connections for continuity and repair if defective. |
| Engine does not crank (electric start models only) | Insufficient voltage for cranking due to battery not charged | Check condition of battery and recharge or replace as needed. |
| Engine does not crank (electric start models only) | Insufficient voltage for cranking due to terminal connections loose or dirty | Clean and tighten battery cable connections, starter connections and ground connections. |
| Engine does not crank (electric start models only) | Insufficient voltage for cranking due to defective charge circuit | Check diode and replace if defective. |
| Engine does not crank (electric start models only) | Insufficient voltage for cranking due to defective Ignition Control Unit charge circuit | Refer to Section 6, Engine - Primary Systems for test procedures. |
| Engine does not crank (electric start models only) | Defective starter solenoid or starter | Refer to Section 6, Engine - Primary Systems for test procedures. |
| Engine does not start (recoil start models only) | Defective On/Stop or Engine On/Off switch | Check switch for continuity and replace if defective. |
| Engine does not start (recoil start models only) | Open circuit in wiring between On/Stop or Engine On/Off switch | Check wiring and connections for continuity and repair if defective. |
| Engine does not start (recoil start models only) | Defective Ignition Module | Refer to Section 6, Engine - Primary Systems for test procedures. |
| Engine does not start (recoil start models only) | Low oil level | Check oil level and fill if necessary. |
| Full power switch does not function properly | Defective Full Power switch | Check switch for continuity and replace if defective. |
| Full power switch does not function properly | Wire connections to Full Power switch are not making contact or are miswired | Check for good wire connections and compare connections with wiring diagram in Section 11. |
| Idlematic does not operate (only used on certain models) | Defective Idlematic switch | Check switch for continuity and replace if defective. |
| Idlematic does not operate (only used on certain models) | Wire connections to Idlematic switch, Idlematic Control, or Idlematic Solenoid are not making contact or are miswired | Check for good wire connections and compare connections with wiring diagram in Section 11. |
| Idlematic does not operate (only used on certain models) | Defective Idlematic Solenoid | Check Idlematic solenoid for a binding plunger movement. |
| Idlematic does not operate (only used on certain models) | Defective Idlematic Control | Check to see that the appropriate generator leads pass through the current transformer. Test Idlematic Control. |
| Engine cannot be turned off with switch | Defective Start/On/Stop switch, On/Start switch, or Engine On/Off switch | Check switch for continuity and replace if defective. |
| Engine cannot be turned off with switch | Open circuit in switch wiring | Check wire connections to switch. |
| No AC output voltage (models with automatic voltage regulator) | Open AC circuit breaker | Locate cause of overload and correct as required. Reset breaker. |
| No AC output voltage (models with automatic voltage regulator) | Open circuit between stator main coil and AC receptacle. Defective receptacle. | Check for continuity and correct if circuit is open. Check for defective receptacle. |
| No AC output voltage (models with automatic voltage regulator) | Defective stator main coil | Test stator main coil for open, shorted, or grounded windings and replace if defective. |
| AC output voltage only 6 to 18 VAC (models with automatic voltage regulator) | Defective rotor coil | Test rotor coil for open, shorted, grounded windings and replace if defective. |
| AC output voltage only 6 to 18 VAC (models with automatic voltage regulator) | Defective stator sub coil | Test stator sub coil for open, shorted, or grounded windings and replace if defective. |
| AC output voltage only 6 to 18 VAC (models with automatic voltage regulator) | Faulty brushes or slip rings | Check brushes and replace if defective. Inspect slip rings and clean if needed. |
| AC output voltage only 6 to 18 VAC (models with automatic voltage regulator) | Faulty Voltage Regulator (AVR) | If the rotor and stator test good, and the brush block and slip rings are good, replace the AVR module and recheck. |
| AC output voltage only 6 to 18 VAC (models with automatic voltage regulator) | Faulty permanent magnet in rotor | Replace rotor after checking other possible causes for 6 to 18 VAC. |
| AC output voltage too low or too high (models with automatic voltage regulator) | Engine governor incorrectly adjusted | Check engine speed. Refer to Engine Primary System section. |
| AC output voltage too low or too high (models with automatic voltage regulator) | Faulty voltage regulator (AVR) | Replace the AVR module and recheck. |
| Noisy generator (models with automatic voltage regulator) | Worn rotor shaft bearing | Replace end bearing. |
| Noisy generator (models with automatic voltage regulator) | Rotor and stator rubbing together due to varnish lumps | Check for varnish lumps between rotor and stator and remove as required. |
| Noisy generator (models with automatic voltage regulator) | Rotor and stator rubbing together due to rotor misaligned with crankshaft | Follow specified assembly procedures to correct rotor to crankshaft alignment. |
| Generator overheats (models with automatic voltage regulator) | Generator overloaded due to defective circuit breaker | Replace circuit breaker. Do not exceed specified load when operating set. |
| Generator overheats (models with automatic voltage regulator) | Airflow restricted due to dirt or debris covering vent openings in cover or adapter | Clean away all dirt or debris as required. |
| Generator overheats (models with automatic voltage regulator) | Stator windings covered with oil or dirt | Clean stator windings. |
| Generator overheats (models with automatic voltage regulator) | Defective windings in rotor or stator | Test each component for open, grounded, or shorted windings and replace if defective. |
| Low or no DC output (models with automatic voltage regulator) | Open DC circuit breaker | Locate cause of overload and correct as required. Reset breaker. |
| Low or no DC output (models with automatic voltage regulator) | Open circuit between stator DC coil and diode assembly or between diode assembly and receptacle | Check for continuity and correct if circuit is open. |
| Low or no DC output (models with automatic voltage regulator) | Defective stator DC coil | Test stator DC coil for open, grounded or shorted windings. |
| Low or no DC output (models with automatic voltage regulator) | Defective diode assembly | Test diode assembly for open or short. |
| No AC output voltage (models with capacitor-type voltage regulator) | Open AC circuit breaker | Locate cause of overload and correct as required. Reset breaker. |
| No AC output voltage (models with capacitor-type voltage regulator) | Open circuit between stator main coil and AC receptacle. Defective receptacle. | Check for continuity and correct if circuit is open. Check for defective receptacle. |
| No AC output voltage (models with capacitor-type voltage regulator) | Defective stator main coil | Test stator main coil for open, shorted, or grounded windings and replace if defective. |
| AC output voltage only 3 to 18 VAC (models with capacitor-type voltage regulator) | Defective stator sub coil | Test stator sub coil for open, shorted, or grounded windings and replace if defective. |
| AC output voltage only 3 to 18 VAC (models with capacitor-type voltage regulator) | Defective rotor coil or defective rotor winding diode | Test rotor coil for open, shorted, or grounded winding and defective diode. Replace rotor if defective. |
| AC output voltage only 3 to 18 VAC (models with capacitor-type voltage regulator) | Open or shorted capacitor | Test capacitor for open or short and replace if defective. |
| AC output voltage too low or too high (models with capacitor-type voltage regulator) | Engine governor incorrectly adjusted | Refer to Engine Primary System section. |
| Noisy generator (models with capacitor-type voltage regulator) | Worn rotor shaft bearing | Replace end bearing. |
| Noisy generator (models with capacitor-type voltage regulator) | Rotor and stator rubbing together due to varnish lumps | Check for varnish lumps between rotor and stator and remove as required. |
| Noisy generator (models with capacitor-type voltage regulator) | Rotor and stator rubbing together due to rotor misaligned with crankshaft | Follow specified assembly procedures to correct rotor to crankshaft alignment. |
| Generator overheats (models with capacitor-type voltage regulator) | Generator overloaded due to defective circuit breaker | Replace circuit breaker. Do not exceed specified load when operating set. |
| Generator overheats (models with capacitor-type voltage regulator) | Airflow restricted due to dirt or debris covering vent openings in cover or adapter | Clean away all dirt or debris as required. |
| Generator overheats (models with capacitor-type voltage regulator) | Stator windings covered with oil or dirt | Clean stator windings. |
| Generator overheats (models with capacitor-type voltage regulator) | Defective windings in rotor or stator | Test each component for open, grounded, or shorted windings and replace if defective. |
| Low or no DC output (models with capacitor-type voltage regulator) | Open DC circuit breaker | Locate cause of overload and correct as required. Reset breaker. |
| Low or no DC output (models with capacitor-type voltage regulator) | Open circuit between stator DC coil and diode assembly or between diode assembly and receptacle | Check for continuity and correct if circuit is open. |
| Low or no DC output (models with capacitor-type voltage regulator) | Defective stator DC coil | Test stator DC coil for open, grounded or shorted windings. |
| Low or no DC output (models with capacitor-type voltage regulator) | Defective diode assembly | Test diode assembly for open or short. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Faulty ignition due to worn or fouled spark plug; Faulty ignition due to faulty ignition system; Dirty air cleaner; Restricted fuel flow due to plugged. See the table for the matching fixes.
Documented causes: Faulty ignition due to worn or fouled spark plug; Faulty ignition due to faulty ignition system; Faulty ignition due to faulty plug wire; Lean fuel mixture due to incorrectly adjusted carburetor. See the table for the matching fixes.
Documented causes: Sticking or binding governor linkage; Incorrect governor adjustment; Faulty governor spring; Incorrect fuel mixture due to incorrectly adjusted carburetor. See the table for the matching fixes.