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Stootz01's avatar
Stootz01
Explorer
Oct 06, 2019

Generator dies after load

Been searching for fixes for this for months and the forums that post ideas always die without a fix so here we go.
I have a Onan 4K generator that started out dying after 10 min no matter what.
I installed a new fuel pump/filter and carb, oil change, no fix.
I took the air filter out while it was running to inspect it and noticed it would keep running but when the AC was on it would die...so I changed the air filter...no change under load but it would keep running without a load.
I then took the metal air filter cover and left filter on....would run under load but would then die after 10 min.
I then discovered there was an additional after market fuel filter on it under the RV so I bypassed it, changed the spark plug while I was at it and discovered that it would run for 30 min under load before it died.
I then discovered a youtube video of someone claiming that draining oil below the low level line would keep it going. Comments suggest that was a mirical worker and it seemed to fix the problem for a lot of people.....but not mine....
I'm getting closer to nailing this down but I'm out of ideas

Give me suggestions....I'll do it man!!!!
Gen has 216 hrs on it
Toy Haulers
  • Dirtclods's avatar
    Dirtclods
    Explorer II
    Oct 25, 2019
    joebedford wrote:
    Dirtclods wrote:
    As the load comes on your motor, it should idle up.
    What do you mean 'idle up'? It should be at constant RPM. You might hear a change in note but not rpm as the throttle opens.



    Idle up or reactive load this type of load may require up to three times as much power (wattage) to START as it does to keep it running. Examples of reactive type loads are air conditioners, microwaves "Etc"
  • joebedford's avatar
    joebedford
    Nomad II
    Oct 10, 2019
    Dirtclods wrote:
    As the load comes on your motor, it should idle up.
    What do you mean 'idle up'? It should be at constant RPM. You might hear a change in note but not rpm as the throttle opens.
  • Dirtclods's avatar
    Dirtclods
    Explorer II
    Oct 10, 2019
    As the load comes on your motor, it should idle up. As said above it sounds the choke is cutting it off. Something else to try to see if you have any air leaks while it's running spray some starter fulid around not in, the carb then you'll see if you have any air leaks.
  • lincster's avatar
    lincster
    Explorer
    Oct 07, 2019
    What about the choke?
    I had this same issue with mine and replaced the choke. All good.
  • ksg5000's avatar
    ksg5000
    Explorer
    Oct 06, 2019
    You might try bypassing the low oil sensor - won't cost anything and it will rule out another possibility. Also -check for pinhole leaks in gas line.
  • allcool's avatar
    allcool
    Explorer
    Oct 06, 2019
    Stootz01 wrote:
    Been searching for fixes for this for months and the forums that post ideas always die without a fix so here we go.
    I have a Onan 4K generator that started out dying after 10 min no matter what.
    I installed a new fuel pump/filter and carb, oil change, no fix.
    I took the air filter out while it was running to inspect it and noticed it would keep running but when the AC was on it would die...so I changed the air filter...no change under load but it would keep running without a load.
    I then took the metal air filter cover and left filter on....would run under load but would then die after 10 min.
    I then discovered there was an additional after market fuel filter on it under the RV so I bypassed it, changed the spark plug while I was at it and discovered that it would run for 30 min under load before it died.
    I then discovered a youtube video of someone claiming that draining oil below the low level line would keep it going. Comments suggest that was a mirical worker and it seemed to fix the problem for a lot of people.....but not mine....
    I'm getting closer to nailing this down but I'm out of ideas

    Give me suggestions....I'll do it man!!!!
    Gen has 216 hrs on it

    Have you checked HZ/voltage while running and immediately before unit shuts down..? Very common for a over/under hz safety shut off to occur if governor/engine speed is not set exactly correct. When switching between no load/full load governor struggles to maintain correct rpm to keep hz/voltage in safe/no safety shut down range.

    I set 5500 onans for 62-63hz under no load. When genny goes to full load the rpm drops just enough to drop the hz to 59-60. if it goes below 58-56hz for 10 seconds the unit will shut down on low hz safety shut down... Above 66hz will also trigger a safety shut down. The efi models are a little different but similar...

    Whatever you do, DO NOT drain oil to below low level line and run unit like that utube vid suggests, unless you like rebuilding engines. 1 of the worst web recommendations I've ever heard...lol.

    jmo

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