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michaelhebert19's avatar
michaelhebert19
Explorer
Feb 15, 2018

Onan 5500 Marquis Gold generator problems

Hello all.

I have searched all over the interwebs for this issue and now I am at a loss. I thought it was a fuel issue of some sort but now.....

My problem I am having with the Onan 5500 Marquis Gold onboard generator is that with the cover on and the latch closed, the generator runs for 20 minutes and then shuts off. After 30 minutes or longer, it will start back up and do the same thing, over and over again.

It does this with a load or not and either plugged in or not.

Today I tried taking the cover off and leaving the hatch open and it has been running for 59 minutes at the time of this post without any problems (I have the front AC on, several lights turned on, and a box fan plugged in).

Not really sure what the problem is now. At first I thought it may be a fuel issue. Maybe the fuel pump gone bad or a crack in a fuel line. But now with it running for so much longer than previous times, I am thinking some sort of heat issue.

Any suggestions?
  • gbopp's avatar
    gbopp
    Explorer
    Feb 15, 2018
    How many hours are on the generator? Has it been maintained, oil/filter change, air filter replaced snd generator fuel filter replaced?
    Did you check the rubber fuel lines for cracking?
    Make sure the simple maintenance is complete before you try to diagnose the problem.

    That said, it does sound like it's a heat related issue. But it was designed to run with the hatch closed so, something is affecting the normal operation.
  • j-d's avatar
    j-d
    Explorer II
    Feb 16, 2018
    I'd sure be careful about running the genny any extended period of time without its OEM shrouding in place. It's intended to put the air flow where it needs to be, to cool (careful, j-d typed cooK!) critical components.

    It might help to post complete Model (be sure to include Spec Code!) and Serial Number. We had a few genny techs who'd really dig into our problems, but most of them have migrated. That was largely because we didn't post that Name Plate Info. Model, Spec, Serial, and we often didn't provide a good problem statement or follow up on their advice. Many have stayed active on SmokStak.com

    packpack has stuck with it here, and THANKS!!! One thing we can usually provide is the OEM ONAN Service Manual and it includes Troubleshooting. You know what we need to look up specifics...

    That Flight Systems page is indeed helpful, more for some models than others.
  • bounder39zman's avatar
    bounder39zman
    Explorer II
    Feb 25, 2018
    concur with OP, should not run with cover door off. There is label on gen. base tray stating such. cooling air will be diverted from exhaust system, escaping out door. causing damage to system. this problem is usually a fuel and heat issue. Fuel pump is getting hot or fuel vapor locking at pump inlet...causing shut down. Leaving door off may allow this part of gen to run a little bit cooler, thus it is running longer. Other possibility is that control board is getting too hot, and shutting down circuit that powers fuel pump. See this frequently, and more so as warmer weather arrives. Diagnosing requires removal of fuel line at carb, when problem occurs (be very careful with gasoline here!!!!!). push prime (stop) at switch and see if getting fuel flow (make sure have hose in suitable container to catch any fuel). If fuel pump is running (vibrating, but no flow) then control board is working, and pump probably bad. If pump not running, then check for voltage to pump from control. if no voltage then control bad. It common for these two parts to stop working when get too warm, then work again after cooling down for a little while.

    Make sure that hot discharge air is not recirculating into air intake at bottom of genset

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