Onan 4000 shutting off after 20 min.
Have an Onan 4000 300hrs in a Class C. If I'm sitting still it will run about 20 minutes then sputters and sounds like it's running out of gas and shuts down. If I wait a while it will start back up a...
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Yea I have the prime function. I ran it yesterday and it shut down 4 times. To trouble shoot the fuel pump I tried to start it as soon as it stopped and got it running right away every time but had to prime it. I ran it with no load and ran it with the AC on, same result. That leads me to believe it's not the pump because it would run with no cool down. The weird thing is after the 4th start it ran for 2 hrs until I shut it off because I had to leave. Came back and hour later started it and ran for hours until I finally shut it off. I know my way around an engine just not that familiar with all the different components of an Onan. I can't trouble shoot now if it won't shut down. Going to start it now and then to see what result I get.
Sounds just like mine that I just got fixed. One time on a trip last may it ran overnight no problem, but every night after that it ran for less and less time.
You can replace the coil fora bout $35.
You can replace the Ignition Control Module for about $100.
You can replace the starter for about $35.
An inline spark tester is about $10.
If you find you are getting no spark when it shuts down, I would probably just replace the coil and ICM from the get-go. It's possible it's the voltage regulator ($250) or the control board ($200) but Flight Systems will test those for you at $35 a piece and the testing fee is waved if you buy a replacement from them.
But if I got no spark and had to do it over again, I'd just drop $150 and replace both the coil and ICM from the get-go. They are easy to replace. You have to crank the engine to the right spot so that the short cooling fin lines up with the ICM or the ICM won't come out of the housing. That's the only trick.
Make sure you polish your slip rings - resistance at the brushes should be around 20 ohms and if you get higher than 80 you risk frying the voltage regulator. Flight Systems make a Slip Stick ($20) you can use to reach in and polish the rings or you can do it with a dowel rod and some brown Scotchbright material and use some dental floss to bind the scrubby to the dowel rod and use that.
Steve
