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.

Oil level in the generator correct? When did you chamge the generator fuel filter?Do the simple things first.

Possibly the oil is thinning out and reducing the oil pressure enough to trip off the generator engine. You may want to try 10W30.

gbopp wrote:Oil level in the generator correct? When did you chamge the generator fuel filter?Do the simple things first.Yes and fuel filter changed 9/14, about 250 hours ago

w4phj wrote:Possibly the oil is thinning out and reducing the oil pressure enough to trip off the generator engine. You may want to try 10W30.But 2 -3 minutes wouldn't be enough for oil to cool that much that it would run another 30, would it?

Romer1 wrote:w4phj wrote:Possibly the oil is thinning out and reducing the oil pressure enough to trip off the generator engine. You may want to try 10W30.But 2 -3 minutes wouldn't be enough for oil to cool that much that it would run another 30, would it?Saw it happen before. Bad oil. Easy to fix.

Generator runs 30 minutes, shuts off | Good Sam Community

16 Replies

cgmartine
Explorer
Aug 13, 2017
Romer1, can you update us and let us know if that worked for you? I just now started having the same issue with my Onan generator, where it would die after 30 minutes with and without a load.
Romer1
Explorer
Jul 23, 2017
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.
MEXICOWANDERER
Explorer
Jul 23, 2017
Fill tank to 100%

ANY change at all it's fuel related. An easy test you lose no money.
Winnipeg
Explorer
Jul 23, 2017
We had a similar problem with a 5ver a few years ago. The gen would run for 20 minutes and then shut down. It would re-start after some cranking and then shut down again in 20 minutes.

After much searching, we found that we had a bad check valve at the fuel tank (located about 30' from the gen). There was enough fuel in the line to run for 20 minutes, then it would get air.

A somewhat easy test it to disconnect the fuel line and run a temporary line to a fuel can. If it runs OK with the substitute fuel supply, then you have located the problem.
allbrandauto
Explorer
Jul 20, 2017
fuel pump fuel pump fuel pump been there
Dennis12
Explorer
Jul 20, 2017
I would say that it's something electrical and the breaker is resetting so that you can restart it, not the oil cooling down. My guess
NC_Roamer
Explorer
Jul 20, 2017
This began happening to our 4KW Onan generator in our class C. Oil was not due for a change, was running the recommended Onan brand multi-weight oil, oil level full and gas tank almost full. It would cut off after thirty minutes. Would restart, but run only a minute before shutting down. Had to let it cool completely before using it again.

Took it to Cummins/Onan service center in Kenly, NC. They replaced the fuel pump and it's been fine since.
YC_1
Nomad
Jul 19, 2017
I would inspect the fuel filter area for a bent hose and while in there I would swap the fuel filter. They can plug easily. At least remove it and blow through it. You could be surprised.
marcsbigfoot20b
Explorer
Jul 19, 2017
Im pretty sure the oil pressure or level is bypassed during cranking as long as you hold the button down.
wra
Explorer
Jul 19, 2017
I saw a similar problem on another blog in this forum. The suggestions were bad fuel pump (to fix, replace the pump) or the gas cap no longer venting. (to check, open the gas cap. If it fixes the problem, replace the cap) Let us know what fixes your problem. Good luck. WRA