Forum Discussion

tkcas01's avatar
tkcas01
Explorer
Oct 22, 2013

Onan 7500 Quiet Diesel - "gallops" when trying to start

When my gen is cold, it starts normally. However, if I try to start it when it is hot, it "gallops", meaning it sounds like it is wanting to start but not quite kicking in, and it jumps somewhat violently. Any thoughts on what this might be a symptom of? It seems like the fuel is igniting too early - maybe as the result of the hot cylinders? I recently replaced the air and fuel filters and that did no good.
  • eHoefler's avatar
    eHoefler
    Explorer II
    Oct 23, 2013
    Normal. It is called " Dieseling". The simple design of the engine is like the old ones unlike today's diesels. It is from incomplete combustion of a cold engine, as the engine starts to warm up, it will burn the fuel more efficiently.
  • nevadanick's avatar
    nevadanick
    Explorer
    Oct 22, 2013
    Sounds to me like it isnt getting fuel, possibly a check valve that when warm lets the fuel bleed off. If it has a primer try priming before you start it when hot and see if that makes it bettter. If so then fuel is bleeding off.

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