Forum Discussion

jeremywatco's avatar
jeremywatco
Explorer
Aug 17, 2014

Onan 4000 dies

Hi all,

I have a new rig with a new Onan 4000 (gas) in it. I have 50 hours on it.

I've had an issue a few times that is quite annoying. I'll have the generator running while driving and occasionally the generator will just shut off and not restart unless its sat for a long time.

The only thing I feel I can correlate to this is that its always happened on a hot day while climbing for a while (thus engine getting a workout).

Could it be that the Onan since it sits right behind the engine is just overheating and thats causing the issues? Usually after a few hours it will start and run like a champ while parked. This issue only seems to be happening while driving.

Also.. I've noticed that occasionally the onan makes a clanking/rattling noise.. it makes the same noise whenever I prime it using the switch but the noise stays on sometimes while generator is running.. maybe a bad fuel pump?

8 Replies

  • jeremywatco's avatar
    jeremywatco
    Explorer
    Aug 18, 2014
    Thanks for all the input.

    Oil levels are good and had 3/4 tank of gas.

    I'm thinking it must be heat related somehow as if I get to a flat spot, pull over and try to restart it will start up but cut off as soon as I let go of start switch. Wait 30min to an hour and it will purr like a kitten.
  • aruba5er's avatar
    aruba5er
    Explorer
    Aug 18, 2014
    Sound to me like the engine low oil switch. Climbing? oil away from switch. Fifty hours, may have used some oil. Dumb question> Did you check oil? I know my Emerald onan 4000 watt used some oil and it would shut off if the oil got hot and thin if too low.
  • ksg5000's avatar
    ksg5000
    Explorer
    Aug 18, 2014
    If problem confined to climbing hills then maybe not enough fuel in gas tank or maybe fuel pump doesn't have enough power to transmit fuel uphill? Heat maybe an issue but I don't recall reading many heat problems with 4000.
  • Kpackpackkelley's avatar
    Kpackpackkelley
    Explorer II
    Aug 18, 2014
    I know miller welders are rated up to 104 ° I'm not sure on onans but it wouldn't be more.
  • jeremywatco's avatar
    jeremywatco
    Explorer
    Aug 17, 2014
    Harvard wrote:
    The fuel pump is a solenoid driven spring loaded piston that gets cocked a couple of times per second whether it needs to be cocked or not. The spring provides the fuel pressure and when you press the primer it should pressure up and the noise should be less when pressured up (shorter stroke when pressured up). If it is always noisy during a prime session then it may be the solenoid is going full stroke all the time because it is not pressuring up properly and that could be because of leaky piston rings or check valve etc etc.


    Now that you say it like that the noise I hear rattling around definitely sounds like a spring going booooiiiiinnnng but at a high rate of speed.

    Not always, usually notice the most when the generator is off level.
  • Harvard's avatar
    Harvard
    Explorer
    Aug 17, 2014
    The fuel pump is a solenoid driven spring loaded piston that gets cocked a couple of times per second whether it needs to be cocked or not. The spring provides the fuel pressure and when you press the primer it should pressure up and the noise should be less when pressured up (shorter stroke when pressured up). If it is always noisy during a prime session then it may be the solenoid is going full stroke all the time because it is not pressuring up properly and that could be because of leaky piston rings or check valve etc etc.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,284 PostsLatest Activity: Jul 14, 2025