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jimdmorrison's avatar
jimdmorrison
Explorer
Jul 26, 2020

Onan QG fuel coming out air filter & oil build pressure

Hey guys,

I replaced my generator with a 2013 Onan QG 4000. I knew it had problems, but it was a great deal. For some reason, starting it builds pressure in the oil. WHen I take off the oil cap, it sprays everywhere.

Fuel was also coming out the air filter, so i replaced the carb, but the fuel is still overflowing there. Any ideas?
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    Jul 26, 2020
    Do you have a "stock" fuel pump ? It sounds like the fuel pump pressure is too high and forcing the float and needle valve assembly open.

    Excess oil is gasoline washing into the crankcase. Drain what is in there and install fresh oil.

    You need to verify that the float and needle are working properly. Rig up plastic pop bottle with a hose pushed through a hole in the cap. Disconnect and plug the hose from the fuel pump and hook up this temporary test fuel "tank". It must hang upside down above the carburetor to that it will gravity feed.

    If the fuel drains out of the pop bottle within 5 to 10 minutes (engine off) the needle vale has failed.

    If the fuel level remains constant for that time, the fuel pump is over pressure.

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