Cummins/Onan ED series troubleshooting: 17 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan ED series — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| Engine misfires at all loads | Fouled spark plugs, Defective or wrong spark plug, Sticking valves, Broken valve spring, Defective ignition wires, Defective or improperly adjusted points, Defective Ignition condenser, Improper Valve lash | Clean and adjust, Replace, Clean stems and guides, Replace, Adjust or replace breaker points |
| Low oil pressure | Oil too light, Oil badly diluted, Oil too low, Oil relief valve not Seating, Badly worn engine bearings | Drain, refill with proper oil, Drain, refill with proper oil, Add oil, Remove and clean, or replace, Replace, Clean all lines and passages, Remove and clean, Replace engine or panel unit |
| Plant starts but does not continue to run | Start button released too soon, Defective charging generator, Defective panel equipment | Hold in contact longer, Repair, See Controls |
| Engine backfires at carburetor | Lean fuel mixture, Clogged fuel screen, Intake air leak, Poor fuel, Spark too late, Spark plug wires crossed, Intake valves leaking | Clean or adjust carburetor, Clean screen, Replace flange gaskets, tighten carburetor, Refill with good, fresh fuel, Retime ignition, Install wires correctly, Grind or replace |
| Excessive oil consumption, light blue smoky exhaust | Sludged rings, excessive bearing clearances, piston skirt collapsed, worn intake valve guides | Replace worn parts, Remove and clean screen, Tighten screws and connections, Drain, refill with correct oil, Replace bearings |
| Black, smoky exhaust, excessive fuel consumption, fouling of spark plugs with black soot, possible lack of power under heavy load | Fuel mixture too rich, Choke not open, Dirty carburetor air cleaner | Be sure all jet gaskets are in place and tight; and float needle valve gasket is in place and tight. Adjust choke. Install needed carburetor parts, adjust float level |
| Light pounding knock | Loose connecting rod bearing, Low oil supply, Low oil pressure, Oil badly diluted | Replace, Add oil, Refer to symptom of low oil pressure for remedies |
| Engine stops unexpectedly | Fuel tank empty, Fuel pump failure, High water temperature, Defective ignition | Refill, Repair or replace, See symptoms for engine overheating, Check the ignition system. Repair or replace parts necessary |
| Dull metallic thud, if not bad, may disappear after few minutes operation. If bad, increases with load | Loose crankshaft | Replace bearings, unless one of the next three remedies permanently corrects the trouble |
| Sharp metallic thud, especially when cold engine first started | Low oil supply, Low oil pressure, Oil badly diluted | Add oil, Refer to symptom of low pressure for remedies, Change oil |
| Pinging sound when engine is rapidly accelerated or heavily loaded | Carbon in cylinders, Spark too early, Wrong spark plugs, Spark plugs burned or carboned, Valves hot, Fuel stale or low octane, Lean fuel mixture | Remove carbon, Retime ignition, Install correct plugs, Install new plugs, Adjust tappet clearance, Use good fresh fuel, Clean or adjust carburetor |
| Engine cranks too stiffly | Corroded terminals, Too heavy oil in crankcase, Weak battery | Clean and tighten terminals, Drain, refill with light oil, Test and recharge or replace battery |
| Engine will not start when cranked | Faulty ignition, Lack of fuel.or faulty carburetion, Clogged fuel screen, Cylinders flooded, Poor fuel, Poor compression, Wrong timing, Poor choking | Clean, adjust, or replace breaker points, plugs, condenser, coil, etc., retime ignition, Refill the tank, Check the fuel system. Clean, adjust or replace parts necessary, Clean, Crank few times with spark plugs removed, Drain, refill with good fuel, Tighten cylinder head and spark plugs, It still not corrected, grind the valves, Replace piston rings, if necessary, Retime ignition, If plant is cold, adjust choke. If plant is warm, pull up on choke arm momentarily, while cranking |
| 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 |
| Current steady but engine not misfiring | Speed too low | Adjust governor to correct speed |
| Engine misfires at light load | Carburetor idle adjustment set wrong or clogged. | Adjust, clean if needed. |
| Engine misfires at heavy load | Spark plugs defective. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Fouled spark plugs, Defective or wrong spark plug, Sticking valves, Broken valve spring, Defective ignition wires, Defective or improperly adjusted points, Defective Ignition condenser, Improper Valve lash. See the table for the matching fixes.
Documented causes: Oil too light, Oil badly diluted, Oil too low, Oil relief valve not Seating, Badly worn engine bearings. See the table for the matching fixes.
Documented causes: Start button released too soon, Defective charging generator, Defective panel equipment. See the table for the matching fixes.