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sand_fiend's avatar
sand_fiend
Explorer
Jul 27, 2013

Onan Microlite 4000 help please.

Hello everyone..

I have a couple of questions to ask.
My friend bought a new onan 4000 because he was having troubles with his old one. he is not mechanically inclined.

I took the carb apart to find it clogged up and cleaned it out.
it started right up. it ran for a few minutes and died.

I have been reading through the form and found a lot of advice.

I found that the fuel pump would stop working after a few minutes. his I also confirmed this with a bench test and letting it run fuel from a gas can and back in to it on a direct power source.
the pump would stop pumping but the pump was making noise like it was working.


I bought a new pump and installed it.
it started right up again. after a half hour it died again.
I unplugged the starter solenoid wire and pushed the start switch. the pump started to pump again. i hooked everything back up and it started fine.

It ran for about a half hour and it died again. this time i loosened the carb drain screw to find no fuel in the carb.

I hot wired the pump directly to the battery and it has been on for about 4 hours now and still going..

It seems like it is loosing power to the fuel pump wire after a half hour or so.

So that is one of my questions. what would cause the wire to loose power after a half hour ?

Also. i have no service book on this. Just what i have read.

I need to know how this generator charges its on battery or if it dose ?
Or dose it rely on the power converter in the trailer to recharge the battery's ??

Thank's phil
  • Roman_Duck's avatar
    Roman_Duck
    Explorer
    Aug 06, 2013
    Handbasket is correct, the geeny produces its own power once its running. It sounds like your voltage regulator is on its way out. I also had rewired the fuel pump so it would run off of the coach batties, and that solved the problem for a little while, then the issue with our genny started again(this time I had fuel, but the genny would only run if I held the start button down. After pulling my hair out I reseached the problem and the gents at flightsytems.com assisted me in troubleshooting. In the end as soon as the genny warmed up the VR (voltage regulator)would short itself out and quit. It started with the fuel pump, but as time went on it effected the gennies voltage to the coil.
  • sand_fiend's avatar
    sand_fiend
    Explorer
    Jul 28, 2013
    sorry, should had said it is out of a 99 motorhome. aprox 500 to 800 hours
  • adayjk's avatar
    adayjk
    Explorer
    Jul 28, 2013
    Wow am I confused. So we are working on a NEW Onan generator here? Or a used replacement? Onan has had a run of bad pumps in 2012 and 2013. Don't rule out another bad pump.

    If the new carb is plugged, the same bad gas that plugged the carb likely plugged the fuel filter. This can cause the symptoms you describe because the filter will plug and the material will settle to the bottom of the filter when the fuel flow is gone. it also means that your "power the pump another way" test may only be a lucky run where the filter didn't replug.

    Rig up a meter and watch voltage at the pump with the engine running, both power and ground at the same time, until it quits. Some off these units have temp and oil pressure switches that can cause a shut down.

    Use a meter to diagnoise a loss of voltage, vs a physical fuel problem. If you can't get it to a state where it won't start you will have to sit there and watch it so you will know if it is one or the other.
  • sand_fiend's avatar
    sand_fiend
    Explorer
    Jul 28, 2013
    4.0 KY-FA/26100H

    when starting. you have to hold the button for a few seconds and it will run on its own. if you disconnect the battery it will die
  • Handbasket's avatar
    Handbasket
    Explorer
    Jul 27, 2013
    Full identifier would be model name, and all info on the data plate.

    _If_ it's a Microquiet from the past decade +, it gets cranking voltage and ignition from the battery, but self-generates to run the ignition & fuel pump once the start button is released. All Micro-series carbs for at least the past 12 years are non-rebuildable.

    Jim, "IRS: Be audit you can be."

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