Forum Discussion

toytacoma8's avatar
toytacoma8
Explorer
Jul 26, 2015

Onan dies in the Heat

Never had any problems with the Microquiet 4000 in our 2006 Victory Lane til last weekend. We were camping and it was about 95 degrees and 4000 feet. Gen ran for the first time about 35 minutes and stumbled and died. Would restart for a few seconds and then not start at all. after an hour or so it would run again but only for about 10 minutes. Did this several times.

In the morning and evening when it was a little cooler it seemed to stay running.

I am guessing vapor lock from what I have read but I have not seen any definitive answers on how to cure it. Add a fan? open up an air duct?

Any ideas?
Toy Haulers
  • WyoTraveler's avatar
    WyoTraveler
    Explorer
    Jul 26, 2015
    Replace fuel pump. Does it throw a code "no fuel"? Many of the Onan's have fuel pump problems caused by heat. If my fuel pump goes out again I'm going to move it away from the generator and mount it on the frame where it is cooler.
  • Vulcanmars's avatar
    Vulcanmars
    Explorer
    Jul 27, 2015
    If it's gas (not LPG) most have an adjustment for higher elevation on the carb. High elevation = lean fuel mix= runs hotter.
    If it continues to die you may have a fuel pump going south.
  • Leftywalker's avatar
    Leftywalker
    Explorer
    Jul 27, 2015
    I wound try running it with the fuel cap off and see if it still does it. If it doesn't quit then find a vented fuel cap. If it does quit then look at fuel pump.
  • lincster's avatar
    lincster
    Explorer
    Jul 27, 2015
    Do you have an altitude adjustment on the carb?
    Need to make sure that is set correctly.
  • Y-Guy's avatar
    Y-Guy
    Moderator
    Jul 27, 2015
    You've been given some good advice. I will say from the fuel pump issues I had with my 5500 I'm not sure that's the issue or not. It's very odd that it's having issues while hot which makes me think it's more related to your altitude setting. But few other things. While looking at the generator itself you can look at the switch for the number of blinks, and get the fault code. Knowing that can really help. I'd also check your oil to make sure it's not dirty as well as your air filter.
  • Dirtclods's avatar
    Dirtclods
    Explorer
    Jul 28, 2015
    Make sure your frig is on gas the auto does not always trip on it own if its running on gas not propane. 2nd that on the fuel I always run the higher octane as well.
  • GL's avatar
    GL
    Explorer
    Aug 04, 2015
    Fuel pump.
    I have an Onan 5500, had an identical problem. Whenever it was hot enough, it would just quit. After it cooled down for a time, I could get it to start back up. On that trip I ended up pointing a small portable fan up at the bottom of the genny (right where the fuel pump is), and it stayed on long enough to get me through that trip.

    I replaced the fuel pump when I got home and haven't had the problem since.
  • Bedlam's avatar
    Bedlam
    Moderator
    Aug 04, 2015
    Vulcanmars wrote:
    If it's gas (not LPG) most have an adjustment for higher elevation on the carb. High elevation = lean fuel mix= runs hotter.
    If it continues to die you may have a fuel pump going south.

    Higher elevations result in a rich burn if jetted for sea level due to less air available. I have noticed more smell from the exhaust on my gasoline 5500 and LPG 2500 at elevation but never had plug fouling to worry about rejetting.

    I agree that a weak/failing fuel pump would cause issues when ambient temperatures are high. Altitude should not effect the pump, but a partially clogged fuel filter or fuel tank vent will make a pump work harder than it should.
  • Dwight45's avatar
    Dwight45
    Explorer
    Aug 24, 2015
    I'm having this problem with a brand new 5500 onan. If I prop open the generator compartment door it runs fine. Close the door and it overheats. Still think it's the fuel pump?

    Dwight

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