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Donught_Lord's avatar
Donught_Lord
Explorer
Jul 09, 2020

Generator only runs if engine is on

Hey there,
So I've been trying to diagnose an issue with my Onan generator for quite some time. It starts and runs for a 5-15 minutes then sputters and dies. Today I was fiddling with it and the battery that turns the starter died so I turned the van engine on and started the generator and set the engine to charge both the house and van batteries so I could keep fiddling. What I found was that after a short while of the generator coughing up smoke and sputtering it ran smoothly and I rejoiced! Alas, my celebration was too soon because I turned the van engine off and surely enough in about 5 minutes the generator sputtered and died.

Has anyone out there had a similar issue or could tell me what I should look for to fix this, it's not very economic to run 2 engines for 1 generator lol :D

4 Replies

  • JoeH's avatar
    JoeH
    Explorer III
    Jul 11, 2020
    What Doug said----- I had an issue where the genset would die after a bit.... it was throwing a fuel pump code. After looking into things, I found that the battery cable that ran 40 ft or so from the chassis battery to the genset wasn't securely attached and would result in an open circuit thus shutting down the genset due to the fuel pump not operating.
    See what code the genset is indicating and start our PD from there.
    Good luck
  • jdc1's avatar
    jdc1
    Explorer II
    Jul 10, 2020
    dougrainer wrote:
    You just joined. Always state Year,Brand and Model of RV. State Model of appliance also. Onan gensets require a constant 12 volt supply to stay running. Your scenario points to either a faulty fuel pick up system install or your Coach battery and charging system is not operating correctly or your coach battery is dead and bad and needs replaced. Gensets do NOT have a battery charge circuit. The battery is charged by your Converter or Inverter/Charger with 120 current supplied by the Genset. Doug


    Exactly. Check your converter to see if it is charging your battery. Then check to see if that battery is holding a charge.
  • dougrainer's avatar
    dougrainer
    Nomad
    Jul 10, 2020
    You just joined. Always state Year,Brand and Model of RV. State Model of appliance also. Onan gensets require a constant 12 volt supply to stay running. Your scenario points to either a faulty fuel pick up system install or your Coach battery and charging system is not operating correctly or your coach battery is dead and bad and needs replaced. Gensets do NOT have a battery charge circuit. The battery is charged by your Converter or Inverter/Charger with 120 current supplied by the Genset. Doug
  • Roger10378's avatar
    Roger10378
    Explorer II
    Jul 10, 2020
    You don't give us much info to start with but here is an idea.

    It sounds like it is starving for fuel. Is the fuel supply from a separate tank or from the van's tank? If from the van tank is it a separate fitting or does it come off the van line? Most modern vehicle engines have the fuel pump in the fuel tank so the line is under pressure. When your van was running the generator ran fine because of a constant supply of fuel. When you shut off the van the pressure goes to zero and the generator cannot suck enough fuel from the tank and dies.

    If this is the case there are two different possible solutions. 1. change the fuel supply line. 2. energize the fuel pump relay so that you have fuel pressure.

    If it is a separate supply this does not apply.

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