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MikeDavies's avatar
MikeDavies
Explorer
Mar 24, 2014

Onan 55 GJAB Gen Set Fuel Filter Problem

When doing the routine monthly startup on our Onan Gen, as soon as it
started the fuel filter that attaches to the carburetor started leaking. I went to an RV Dealer and Repair in Montclair CA with the model number of the Gen. They gave me a different fuel filter than the original. Evidently the filter that was installed had been discontinued. Onan's solution was to use a different filter that is too large diameter to fit in where the old filter sits. They want you to buy what a connector with a threaded connector on one end and a barbed hose fitting on the other, install that into the carb and gas line and install the new filter into the inlet of the fuel pump. I was skeptical because you should have a filter at the carb fuel inlet. Anyway, after following the dealer techs instructions the gen wont start. :( The fuel pump is delivering fuel and there is fuel in the float bowl of the carb, verified by using the float drain on the bottom of the float bowl. I contacted Cummins and verified that the filter and modification is correct. They were very helpful and sent me a drawing of the install. If anyone has had this problem, please let me know
Class A

4 Replies

  • bounder39zman's avatar
    bounder39zman
    Explorer II
    Apr 06, 2014
    Onan (and other genset mfgrs) were having filter leakage problems with that type filter. Since the Onan also had a filter at the fuel pump inlet, they decided that the filter at the carb was redundant, and supplied the fitting to install to do away with the one at the carb. If you have fuel in carb. bowl, and unit will not start, have you checked spark at spark plugs? also, check wire plug at fuel cut solenoid in float bowl...it can get loosened while you were changing filter. The fuel-cut solenoid plunger can also get stuck (esp if any water or rust in bowl) and not let fuel flow from bowl to ports in carb.
  • MikeDavies's avatar
    MikeDavies
    Explorer
    Mar 25, 2014
    othertonka wrote:
    I had the same problem with the original filer leaking and did the same repair you describe using the adapter at the CARB. And it has worked for me.
    Here is a link to the adapter that takes the place of the original filter
    Onan adapter


    Hi,
    Yes I always have to prime it to start it. I pulled the fuel line from the carb to check to pump, plenty of gas. Checked the float bowl drain, plenty of gas there. I'm thinking that changing the filters kicked up some gunk and plugged up the carb. You will find plenty of posts on that problem with the Onan.
    Take Care
  • othertonka's avatar
    othertonka
    Explorer
    Mar 24, 2014
    I had the same problem with the original filer leaking and did the same repair you describe using the adapter at the CARB. And it has worked for me. Have you used the primer ? Just push and hold down the "Stop/Prime" button for 20 or 30 seconds and you will hear the fuel pump click and pump fuel into the Carb. When the pump slows down, push the "Start button" until it starts. Might take 20 seconds to start.
    Here is a link to the adapter that takes the place of the original filter
    Onan adapter

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