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Apollo11sailor's avatar
Apollo11sailor
Explorer
Aug 22, 2015

Onan fuel pump or carb

My Onan 4000 model KY L with 170 hours will start and run for a couple of minutes then it dies. Acts likes it is running out of gas.

Knowing that the fuel tank was full I suspected the fuel pump. I disconnected the fuel input line from the filter and connected a short hose that I inserted into a gas container. Then pressed the Stop button to prime, worked fine. Next pressed the start switch and the unit started and ran fine for three or four minutes till I shut it down. Thinking that this confirmed that the pump was OK I put everything back together and restarted the unit. After about two minutes the unit started to sputter or surge. Did that for about 30 seconds and then died. I immediately disconnected the carb input goes and there was no fuel evident.

Is it possible that the pump has degraded and can no longer sufficiently pump fuel from the tank. It seemed to work fine when I tested direct from a container from about two feet.
  • j-d's avatar
    j-d
    Explorer II
    Aug 22, 2015
    Apollo11sailor wrote:
    My Onan 4000 model KY L with 170 hours...

    Is it possible that the pump has degraded and can no longer sufficiently pump fuel from the tank?


    Spec L and 170 hours...How Old? Still Warranty? Have you been using it regularly or at least giving it a monthly exercise?

    What Trouble Code is blinking on your Start/Stop switch or Control Panel?

    If it's young with low hours, pump failure isn't likely. Still any part can fail prematurely. But... If the coach stands without genset use, especially without stabilized gas, carb trouble can develop within a couple months.

    We had a gunked up carburetor. I could start it and it'd run under load till the load came off. Example, would carry air conditioner compressor (heavy load) till it cycled off, leaving only air conditioner fan (light load). Then it'd quit. The idle passages were clogged. Don't forget, the genset runs at a steady 3600-RPM, BUT! at light or no load, the small idle passages come into play even if it's still running 3600. Apply a load and it's still running 3600 but on larger passages that don't clog as easily.

    The gas tank is full. OK, now can you check to make sure you don't have a loose clamp or pinhole leak spot?

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