Cummins/Onan 5KW GO troubleshooting: 85 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 5KW GO — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| Generator overheating | Overloaded | Reduce load |
| Generator overheating | Brush rig out of position | Be sure to line up marks. See Brush Rig |
| Voltage drops under heavy load | Engine lacks power | See remedies for engine misfiring under heavy load |
| Voltage drops under heavy load | Poor compression | Tighten cylinder head and spark plugs. If still not corrected, grind the valves. Replace piston rings, if necessary. Refer to MAINTENANCE AND REPAIR |
| Voltage drops under heavy load | Faulty carburetion | Check the fuel system. Clean, adjust or replace parts necessary |
| Voltage drops under heavy load | Restricted air cleaner | Clean and refill |
| Voltage drops under heavy load | Excessive choking | See that choke opens properly |
| Voltage drops under heavy load | Carbon in cylinder | Remove carbon |
| Voltage drops under heavy load | Restricted exhaust line | Clean or increase the size |
| Engine misfires at light load | Carburetor idle adjustment set wrong or clogged | Adjust, clean if needed |
| Engine misfires at light load | Spark plug gaps too narrow | Adjust to correct gap. Refer to TABLE OF CLEARANCES |
| Engine misfires at light load | Intake air leak | Tighten or replace gaskets |
| Engine misfires at light load | Faulty ignition | Clean, adjust, or replace breaker points, plugs, condenser, coil, etc., or retime ignition |
| Engine misfires at light load | Uneven compression | Tighten cylinder head and spark plugs. If still not corrected, grind valves. Replace piston rings, if necessary |
| Engine misfires at light load | Worn intake valve stems or guides | Replace valves or guides |
| Engine misfires at light load | Spark plugs defective | Replace |
| Engine misfires at light load | Clogged carburetor | Clean jets |
| Engine misfires at light load | Clogged fuel screen | Clean |
| Engine misfires at light load | Defective spark plug cables | Replace |
| Engine misfires at all loads | Fouled spark plug | Clean and adjust |
| Engine misfires at all loads | Defective or wrong spark plug | Replace |
| Engine misfires at all loads | Sticking valves | Clean stems and guides |
| Engine misfires at all loads | Broken valve spring | Replace |
| Engine misfires at all loads | Defective ignition wires | Replace |
| Engine misfires at all loads | Defective or improperly adjusted points | Adjust or replace breaker points. See Periodic Service - Weekly |
| Low oil pressure | Too long screw on center main bearing | See MAIN BEARINGS |
| Low oil pressure | Oil too light | Drain, refill with proper oil. See PREPARATION |
| Low oil pressure | Oil badly diluted | Drain, refill with proper oil |
| Low oil pressure | Oil too low | Add oil |
| Low oil pressure | Oil relief valve not seating | Remove and clean, or replace. See LUBRICATION SYSTEM |
| Low oil pressure | Badly worn bearings | Replace. See MAINTENANCE AND REPAIR |
| Low oil pressure | Sludge on oil pump screen | Remove and clean |
| Low oil pressure | Badly worn oil pump | Replace |
| Low oil pressure | Defective oil pressure gauge | Replace |
| High oil pressure | Oil too heavy | Drain, refill with proper oil. See PREPARATION |
| High oil pressure | Clogged oil passage | Clean all lines and passages |
| High oil pressure | Oil relief valve stuck | Remove and clean. See LUBRICATION SYSTEM |
| High oil pressure | Defective oil pressure gauge | Replace |
| Plant starts but does not continue to run | START button released too soon | Hold in contact longer |
| Plant starts but does not continue to run | Defective panel equipment | See Controls |
| Engine backfires at carburetor | Lean fuel mixture | Clean carburetor |
| Engine backfires at carburetor | Clogged fuel screen | Clean screen |
| Engine backfires at carburetor | Intake air leak | Replace flange gaskets, tighten carburetor |
| Engine backfires at carburetor | Poor fuel | Refill with good, fresh fuel |
| Engine backfires at carburetor | Spark too late | Retime ignition. See IGNITION TIMING |
| Engine backfires at carburetor | Spark plug wires crossed | Install wires correctly. See IGNITION TIMING |
| Engine backfires at carburetor | Intake valves leaking | Grind or replace. See VALVE SERVICE |
| Excessive oil consumption, light blue smoky exhaust | Worn piston rings | Install new piston rings. See PISTON RING REPLACEMENT |
| Excessive oil consumption, light blue smoky exhaust | Oil leaks from engine or connections. This does not cause smoky exhaust | Replace gaskets or leaking tubing. Tighten screws and connections |
| Excessive oil consumption, light blue smoky exhaust | Oil too light or diluted | Drain, refill with correct oil. See PREPARATION |
| Excessive oil consumption, light blue smoky exhaust | Too large bearing clearances | Replace bearings. See MAINTENANCE AND REPAIR |
| Excessive oil consumption, light blue smoky exhaust | Oil pressure too high | Refer to symptoms of high oil pressure for remedies |
| Excessive oil consumption, light blue smoky exhaust | Breather cap clogged | Clean. See CRANKCASE VENTILATION |
| Excessive oil consumption, light blue smoky exhaust | Engine misfires | Refer to symptoms of engine misfires |
| Excessive oil consumption, light blue smoky exhaust | Faulty ignition | Clean, adjust, or replace breaker points, plugs, condenser, coil, etc., or retime ignition |
| Excessive oil consumption, light blue smoky exhaust | Unit operated at light or no load for long periods | No remedy needed |
| Excessive oil consumption, light blue smoky exhaust | Too much oil | Drain excess oil |
| Black, smoky exhaust, excessive fuel consumption, fouling of spark plugs with black soot, possible lack of power under heavy load | Fuel mixture too rich | Adjust choke, install needed carburetor parts, adjust float level |
| Black, smoky exhaust, excessive fuel consumption, fouling of spark plugs with black soot, possible lack of power under heavy load | Choke not open | See that choke opens properly. See ADJUSTMENTS |
| Black, smoky exhaust, excessive fuel consumption, fouling of spark plugs with black soot, possible lack of power under heavy load | Dirty air cleaner | Clean, refill to proper level |
| Engine runs but current does not build up | Poor brush contact or dirty commutator or slip rings | See that brushes seat well, are free in holders, are not worn too short, and have good spring tension |
| Engine runs but current does not build up | Open circuit, short circuit, or ground in generator | See GENERATOR, replace part necessary |
| Current unsteady but engine not misfiring | Speed too low | Adjust governor to correct speed |
| Current unsteady but engine not misfiring | Poor commutation or brush contact | See that brushes seat well on commutator and slip rings, are free in holders, are not worn too short, and have good spring tension |
| Current unsteady but engine not misfiring | Loose connections | Tighten connections |
| Current unsteady but engine not misfiring | Fluctuating load | Correct any abnormal load condition causing trouble |
| Tapping sound | Tappet clearance too great | Adjust or replace tappets |
| Tapping sound | Broken valve spring | Install new spring |
| Hollow clicking sound with cool engine under load | Loose pistons | If noisy only slight and disappears when engine warms up, no immediate attention needed. Otherwise replace worn parts |
| Voltage low at far end of line but normal near power unit | Too small line wire for load and distance | Install larger or extra wires or reduce load |
| Motors run too slowly and overheat at far end of line but OK near power unit | Too small line wire for load and distance | Install larger or extra wires, or reduce load |
| Noisy brushes | High mica between bars of commutator | Undercut mica. See GENERATOR |
| Excessive arcing of brushes | Rough commutator or rings | Turn down |
| Excessive arcing of brushes | Dirty commutator or rings | Clean. See GENERATOR |
| Excessive arcing of brushes | High mica | Undercut mica |
| Excessive arcing of brushes | Brush rig out of position | Line up marks on brush rig and support |
| Engine overheating | Low water in radiator | Refill radiator |
| Engine overheating | Overloaded | Remove part of load |
| Engine overheating | Improper lubrication | See Low Oil Pressure |
| Engine overheating | Radiator obstructed | Clean radiator |
| Engine overheating | Ignition timing late | Adjust. See IGNITION TIMING |
| Plant will start but does not continue to run | Trouble in one of the relays, the high water temperature switch, or a loose connection (runs with ignition switch at HAND START position) | |
| Plant will start but does not continue to run | Open circuit between the generator and the stop relay (prevents running with ignition switch at ELEC. START position) | |
| Charge ammeter shows a discharge of approximately 7 amps when the plant is stopped | Failure of the reverse current relay (charge relay) | Clean the contact points with a hard finish paper; replace the relay with a new one if cleaning does not remedy the situation |
| Start circuit remains closed after the plant starts, allowing excessively high voltage to reach the batteries | Failure of the start disconnect relay to operate |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Carburetor idle adjustment set wrong or clogged; Spark plug gaps too narrow; Intake air leak; Faulty ignition. See the table for the matching fixes.
Documented causes: Worn piston rings; Oil leaks from engine or connections. This does not cause smoky exhaust; Oil too light or diluted; Too large bearing clearances. See the table for the matching fixes.
Documented causes: Too long screw on center main bearing; Oil too light; Oil badly diluted; Oil too low. See the table for the matching fixes.