onan generator won't run for long under load

Wow! I decided to change the oil for the first time since I bought the motor home. Three years and 100hours of use ago. It's working perfectly now!
Thanks everyone for your suggestions. I guess it was the oil pressure switch?

Here is a troubleshooting guide for your genny

http://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf

All right thanks! I'll do the fuel test thing first, if it pumps fuel well then I'll try replacing voltage regulator.

Run it under load until it shuts down. Immediately check the fuel line at the carb for fuel. If there's none, you've almost surely got a fuel pump failure. That was my first diagnostic procedure last year when I suspected pump problems on my Onan 2800; worked first try.

Another likely culprit is the voltage regulator. If you've got the service manual & a volt-ohm meter, there are step-by-step procedures in the manual for troubleshooting.

I also had a spark arrestor partly plug up once with somewhat similar results, but it'd restart immediately. Dunno if your 4000 has one or not.

Jim, "I'm not hard of hearing. I'm hard of listening."

I had the same problem, turned out to be voltage reg. If voltage gets to far off it will shut down.

jonathanteller wrote:
No ,I don't believe so. There are no leds

Not familiar with you model. Some generators throw codes at the dash where you push to start the generator. I would check manual. If no manual check out Onan's web site you may be able to down load a manual.

Model #onan 4.0 ky-fa/ 26100h
Serial# B 9800608881

No ,I don't believe so. There are no leds

Please post the entire Model and Serial numbers. The last character of Model is called Spec and it's very important in troubleshooting an ONAN.