ONAN 4000 GenSet

There have been a couple of reports of fixes made by replacing the fuel pump which allegedly was a weak spot on certain Onans. I'm about to replace mine soon as I have had some issues with it in hot weather - quitting after 10 minutes or so.

Not all Onans have the prime function. The start/stop switch will say "stop/prime" on the switch if you have the prime function.

Richard

I was referring to the switch on the genset, and looks like you'd already tried that. I think you're right. A call to ONAN is the next step. When you say it "didn't work," though, does that mean you didn't get the tic-tic-tic-tic sound of the priming pump, or you did get that sound, ran it until the sound indicated that priming was complete, and the generator still won't start? Either way, I guess, call the manufacturer, but I'm curious to know how this works out.

i'm confused about the switch you are speaking i have two starting switches one on the dash and one on the generator. i have tried both in the way you said and didnt work. im sure there is a way to prime it, it would make sense i just cant figure it out. i am going to try to reach the manufacture i guess.
thanks for your advice
Ron

srwscott1951 wrote:
@ pap pappy
the start switch on mine is a combo start/stop switch pushing in the reverse of start dosent do anything. i tried it anyway and still no start i feel like its a priming thing but i cant figure out how to prime it

Hmmm. Did you try the priming function on the switch on the genset itself? (I.e., take off the cover, push that switch the opposite of "START" and listen for the priming pump?) It may take a while before the sound of the priming pump gives you an indication that the carb is fully primed. I guess not all ONAN's have a priming function, but maybe it's worth a shot.

@ pap pappy
the start switch on mine is a combo start/stop switch pushing in the reverse of start dosent do anything. i tried it anyway and still no start i feel like its a priming thing but i cant figure out how to prime it

I had the same problem. My fuel gage isn't that accurate so when the generator quit I didn't think it was the amount of fuel, I was wrong. After I put more gas in the generator ran fine, I let it run for about two hours, no problem. Then about two days later it started and ran for about 5 minutes and quit, wouldn't restart. I checked everything, then I remembered from my lawn mower days and I removed the air cleaner, started right up. Took the air cleaner element into the garage and blew it out with compressed air and the generator now works fine.

You should be able to "prime" the system with the pump. If you push the start switch (on the engine) the opposite way that it normally goes, it should run the fuel pump......run it until you hear it labor a bit, then try starting the engine.

Once you get it started, you should be able to start/stop from the inside switch.