Code 33
Onan
Overcrank / Failure to Start
Generator shuts down; Code 33 displayed indicating overcrank (too many failed start attempts)
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
No fuel supply or closed fuel shutoff valve, Air in fuel system (diesel), Faulty ignition system (spark plug, coil) on gasoline units, Clogged fuel filter or carburetor/injector issues
How to Fix / Troubleshooting
Safety first: Disable auto-start. Avoid repeated cranking to prevent starter and battery damage. Ensure area is well ventilated to avoid fuel vapor buildup.
- Verify fuel supply: Check that the main fuel shutoff valve is open and that the fuel tank has adequate fuel. For LP/natural gas, ensure gas supply valves are open and gas pressure is within spec.
- Inspect fuel filter: Replace the fuel filter with an Onan-approved filter if it is old or suspected clogged.
- Bleed diesel fuel system: On diesel models, use the manual priming pump or bleed screws per the service manual to remove air from the fuel lines and injection pump.
- Check ignition (gas units): Remove and inspect spark plugs. Clean or replace if fouled or worn. Check ignition coil connections.
- Carburetor/injectors: If fuel and ignition are good but the engine still will not start, the carburetor (gas) or injectors (diesel) may be restricted and require cleaning or professional service.
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Repair Difficulty
Medium
3/5
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