Generator

I ran across several articles, reviews, etc. referring to a fairly common problem with the fuel pumps. They would stop working after 20 minutes or so, cool down a bit, work again for a few minutes, shut down again, and so on. Those are my symptoms exactly! I went ahead and ordered an Airex E11015 fuel pump ( about $60 from Northern auto parts). I also have a new fuel filter coming, as well as the adapter to replace the carb mounted fuel filter. We'll see if these parts will eliminate the problem.

I will assume you have checked the oil level and the oil is fresh. I had a similar Gen - maybe the same one now that I think about it - quit on me one day. Had the oil changed along with the oil filter and the air filter replaced and it worked just fine after that. I was always careful to change the oil and filter once a year or 100 hours after that and never had another failure.

Here's a very good troubleshooting guide...

Onan Tblshtn guide.

My Onan marquis Gold 5500 on a 2007 model Intruder is doing the exact same thing. Runs 15 - 20 minutes and quits. Very hard to start after it quits. Spray some WD40 down the throat while cranking and it will fire. It has always done fine before today. I just started researching.I appear to have the old style fuel filter that attaches to the carb. It may be original, I don't know, I'm not the original owner. I'm thinking I will replace the filter( maybe with the adapter and inline filter?) and see if that eliminates the problem. And I'm going to see if I can locate where the fuel pump is so I can replace that if need be. I need to do more research.

OK, thanks for all the info. Yes, it was set for high altitude, don't know how that was, but moved it back to about 2000 feet. No change
Cleaned the fins real good. No change.
It starts right up cold, runs great for about 20 minutes then quits, won't start again till it cools down. then runs about 15 minutes quits again.
Still looking for the fuel pump, according to the booklet it's electric, when you prime you can hear it running. Tried to get an RV place yesterday to check it out. He informed me he doesn't do any thing to them except change the oil and didn't know any place close by that works on them. I sure hate to drive all the way to Dallas but if all else fails maybe I will. Thanks again.

Get a high volume air compressor and clean the fins on the cylinders.

The Onan 5000 gasoline generator has a lever on the carburetor to lean out the fuel mixture at high altitudes. If this lever is in the lean position and you are at low altitude, it may be running too lean causing it to overheat.

ONANS HAVE BAD FUEL PUMP PROBLEMS MINE DID SAME THING REPLACED FUEL PUMP ON FRAME NOT HARD TO DO ONAN FUEL PUMP 102 DOLLARS