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Romer1 · 07-19-2017, 11:24 AM

My Onan NHE 6500 just started with this problem. Starts fine and will run for 30 minutes with a/c on. Shuts off and will restart if I wait about 3 minutes and runs for another 30 or so minutes. If I try to start it before the 3 minutes, starter cranks but engine won't catch. Gas tank is over 3/4, oil is full, new air cleaner, so I'm at a loss.

APhotoWizard · 07-19-2017, 12:10 PM

Sounds like a clogged fuel or air filter. Since you have a new air filter, I would look for a clogged fuel filter. Another possibility is a clogged air intake so it is overheating , but I would put my money on the fuel filter.

marjoa · 07-22-2017, 08:35 AM

I had this happen on mine. The generator would run fine for a little while then as it got hot and especially when I put a load on it (which now the generator needs more fuel), it would die. Come to find out I had a weak fuel pump and was on it's way out. When this happened to me, I first was getting code 35 but then it went to "no codes" at all. I replaced the fuel pump and it's ran great ever since. My guess it's your fuel pump. I'd change both fuel pump & filter while you're at. Get on Amazon. You'll also need to buy 2' of 1/4" fuel line & 2 new hose clamps because when you trim off the ends of the crimped old fuel line, there's not enough length to reconnect. You can buy these items at a local auto parts store.

Circled in red is the fuel filter and in front of that is the fuel pump. Use "gently" a pair of vice grips and squeeze the fuel line in front of the fuel filter to shut off the fuel before your start disassembly.

Romer1 · 07-22-2017, 02:06 PM

Thanks for all the replies.
I decided to try changing the oil from a multi viscosity synthetic to a straight SAE 30.
Generator was still running under heavy load 2.5 hours later. The only other difference was ambient temperature was 84 instead of 90.
Will see if this really solved the problem.