Forum Discussion

hotjag1's avatar
hotjag1
Explorer II
Jan 30, 2022

Onan diesel generator quits after a few minuthes

I browse this forum fairly often, but now I need some advice or expertise on what is wrong with my generator.

It is a 6500 watt Onan. It starts up fairly quickly and generates power within a couple of minutes of running time, but it shuts down after about 5 minutes of run time with or without any load on it. It will restart after about a minute, but runs rough as it starts and then smooths out after about 5 seconds.
It will then run for about 5 minutes before shutting down again. I suspect that it is not getting enough fuel, although it was serviced with oil change, new fuel and air filter about 6 months ago. All suggestions are welcome.
  • Reisender's avatar
    Reisender
    Nomad
    Jan 30, 2022
    gbopp wrote:
    Reisender wrote:
    Gas or diesel?

    It says Onan Diesel Generator in the title of the post.


    Ugh. Doh. My apologies.

    So this is what I want you to do. Get your iPhone out and start your stop watch as soon as it starts. Then see if it quits at exactly 5 minutes. If so, I think I know what it is.
  • gbopp's avatar
    gbopp
    Explorer
    Jan 30, 2022
    Reisender wrote:
    Gas or diesel?

    It says Onan Diesel Generator in the title of the post.
  • CA_Traveler's avatar
    CA_Traveler
    Explorer III
    Jan 30, 2022
    Does it throw a code - flashing lights? It could be frequency or AC voltage problem. Model?
  • Reisender's avatar
    Reisender
    Nomad
    Jan 30, 2022
    hotjag1 wrote:
    I browse this forum fairly often, but now I need some advice or expertise on what is wrong with my generator.

    It is a 6500 watt Onan. It starts up fairly quickly and generates power within a couple of minutes of running time, but it shuts down after about 5 minutes of run time with or without any load on it. It will restart after about a minute, but runs rough as it starts and then smooths out after about 5 seconds.
    It will then run for about 5 minutes before shutting down again. I suspect that it is not getting enough fuel, although it was serviced with oil change, new fuel and air filter about 6 months ago. All suggestions are welcome.


    Gas or diesel?
  • Matt_Colie's avatar
    Matt_Colie
    Explorer II
    Jan 30, 2022
    It sure sounds like a fuel system issue to me. Most like there is a very serious restriction in the low pressure side of the system. That could be anyplace between the tank's fill neck and the inlet to the fuel lift pump.

    The poor thing keeps trying to pump and draws a vacuum on the system up until it can't. Then, once shut down, fuel fills in the vacuum. I can't begin to tell you where to look except before the lift pump.

    Matt - 60yr a diesel engineer

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