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bobkatmsu's avatar
bobkatmsu
Explorer
Feb 25, 2016

Onan 5500 generator problem

I have an Onan 5500 generator in my gas 2007 Safari Simba. The fuel tank is full, the fuel pump and filters have all been changed in the past month.
The generator starts as normal and runs same for approximately 5 minutes. Then it shuts off. It will start again without any problem and will run for another 5 minutes then stop. The code that it is putting out is 14, which according to the manual is "overfrequency fault" and recommend taking to dealer. I am leaving in a few days and the local dealer says he can't look at it for at least a week. Any ideas would be appreciated.
Class A

9 Replies

  • jhilley's avatar
    jhilley
    Explorer
    Feb 26, 2016
    jerry8mm wrote:
    I have an Onan 5500 and it did about the same thing. After replacing the fuel pump and the fuel filter (which didn't help), I found that the problem was that it was shutting off because of no oil pressure. There is an oil pressure switch that will shut the engine off if the oil pressure doesn't come up in a reasonable amount of time.

    The oil level was halfway between the full and the add oil mark. I added oil and it works fine. While I was at it, I add an oil pressure gauge.


    Where did you put the gauge/
  • bobkatmsu's avatar
    bobkatmsu
    Explorer
    Feb 26, 2016
    As I am a firm believer in trying the simplest fix first, I went this morning and checked the oil. It was a little low, so added some. Then used carb cleaner and sprayed on linkages, followed that with a shot of silicon. Fired it up and ran it for an hour without any problems. So maybe that's all it needed. I am bringing it over to the house Sunday to pack, I'll let it run longer at that point. I'll keep my fingers crossed and let you know if I have any further problems.
  • jerry8mm's avatar
    jerry8mm
    Explorer
    Feb 26, 2016
    I have an Onan 5500 and it did about the same thing. After replacing the fuel pump and the fuel filter (which didn't help), I found that the problem was that it was shutting off because of no oil pressure. There is an oil pressure switch that will shut the engine off if the oil pressure doesn't come up in a reasonable amount of time.

    The oil level was halfway between the full and the add oil mark. I added oil and it works fine. While I was at it, I add an oil pressure gauge.
  • jwmII's avatar
    jwmII
    Explorer
    Feb 25, 2016
    Someone else on here mentioned cracked fuel line. Before spending a bunch of money go ahead and replace the fuel line from the fuel tank to the generator fuel pump. All of this is assuming your generator is not propane powered. Cracked fuel lines are largely responsible for the symptoms you have. Sucking air into a fuel line starves the engine for fuel.
  • Sam_Spade's avatar
    Sam_Spade
    Explorer
    Feb 25, 2016
    bobkatmsu wrote:
    I am leaving in a few days and the local dealer says he can't look at it for at least a week. Any ideas would be appreciated.


    It that is a local RV dealer, I probably wouldn't trust them anyway.
    Look up a Cummins dealer near you.
    A quick search at "http://power.cummins.com/sales-service-locator"
    showed about 8 of them.
  • Busskipper's avatar
    Busskipper
    Explorer
    Feb 25, 2016
    Think the advice given is likely good - but on occasion low oil could also be the issue.

    If the problem happened as a result of the filters being changed then look for a bad seal,(Air).

    Do the simple things first,

    BOL,
  • mfox20's avatar
    mfox20
    Explorer
    Feb 25, 2016
    On my 2000 5500 with similar symptoms, it turned out to be cracked fuel lines.

    When you Google "onan generator over frequency fault" you can see most of the responses point back to gummed up Carb along with a few other possible issues.

    Good luck and let us know what you find out.
  • Clay_L's avatar
    Clay_L
    Explorer
    Feb 25, 2016
    That fault would be due to the engine rpm increasing. The governor linkage might be faulty or need lubrication.

    You can download the service manual HERE

    and a trouble shooting guide HERE

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