Common fuel-pump symptoms
- Cranks normally but will not start after storage.
- Starts after priming, then dies after a short run.
- Runs unloaded but quits when the air conditioner or battery charger loads it.
- Runs better with a full RV fuel tank than at lower tank levels.
- Prime sound changes, sounds weak or never seems to fill the carburetor bowl.
Check the simple fuel path first
Verify the motorhome fuel tank is above the generator pickup level and any shutoff valve is open. Inspect fuel lines from outside for cracks, kinks and age. Replace filters only with the correct part and direction. Do not use clear temporary hose or unsafe containers around a running generator.
Do not blame the pump too fast
Stale gasoline, varnished carburetor passages, a plugged filter, cracked suction hose, bad ground or weak start voltage can mimic fuel-pump failure. The pump needs correct voltage and a clear supply path before it can be judged fairly.
When service should test it
A technician can safely measure pump output, voltage supply and fuel flow according to the manual. Pump replacement is straightforward on some models and miserable on others, but guessing is still more expensive than testing.
Related pages
- Onan generator starts then dies
- Onan generator code 36
- Onan carburetor problems
- Onan 4000 won't start
- Generator troubleshooting guide
Sources and review notes
Fuel testing and replacement procedures vary by generator model/spec. Use the official operator and service information for the installed set; Cummins lists common manuals at its RV generator manuals page.