I have a Onan Microlite 4000 generator that will run as long as I hold the start switch on but quits as soon as I release the switch. It is also not generating power. Where should I begin to look for the problem?. Thanks

Do you have a heavy load on the generator ? like a heater,AC ?Does the generator start & run with the breaker off?The generator normaly starts with the 12Volt for the fuel pump from the battery. After you let go of the start button,the generator has to supply the 12 volt for the fuel pump.That is about all I remember from my former Itasca MH with the Onan 4Kgenerator.Siggy

If shutting the breaker off still does not permit the generator to continue to run a W.A.G. makes me remember an Onan that had a shorted neutral output wire. Time for a generator shop I'm afraid.If the gen breaker is a pop-out type what happens when you crank without holding the button in?

I don't have a load on the generator and it still quits running with the circuit breaker on or off

Have you read the codes? This genset self-analyzes to some extent. I've had one start and not make the transition to 3600 RPM no-load conditions, codes said to check ignition and fuel systems.I've had it start, get up to speed, and cut off immediately, codes indicated load electrical problems. In that case I found one of the RV branch circuits had a short to ground. Codes are a blinking pattern after it quits. Interpretations are in the owner's manual.

If you have an older 4K Onan like the KY series they work on a 'voltage in / voltage out' basis, if you put 12+ volts in, you will get 120 volts back out. If the voltage in the house battery is below 12 volts though the output voltage would be too low and so the Onan just stops the output and shuts down. A battery as low as 9 volts will start that little engine, but isn't enough to operate the generator safely. Holding the start button bypasses the shutdown function.If you have someone else to help you, try starting it with the chassis engine running and the emergency start button held down. The increased voltage from the chassis might just do the trick.

Onan Microlite 4000 Issues | Good Sam Community

12 Replies

MEXICOWANDERER
Explorer
Nov 20, 2016
If shutting the breaker off still does not permit the generator to continue to run a W.A.G. makes me remember an Onan that had a shorted neutral output wire. Time for a generator shop I'm afraid.

If the gen breaker is a pop-out type what happens when you crank without holding the button in?
siggyd777
Explorer
Nov 20, 2016
Do you have a heavy load on the generator ? like a heater,AC ?
Does the generator start & run with the breaker off?
The generator normaly starts with the 12Volt for the fuel pump from the
battery. After you let go of the start button,the generator has to supply the 12 volt for the fuel pump.
That is about all I remember from my former Itasca MH with the Onan 4K
generator.
Siggy

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Onan Microlite 4000 Issues

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