4000 Onan won’t run with vehicle running

[SylverSprings]

We have a 2025 GS Conquest E450 with a 4000 Onan generator.

The generator will start and run only for a few minutes when the truck is running.

Fuel tank shows 5/8 full

Any ideas?

 

[THenne1713]

Maybe main engine run not related, issue is (usually) a bad GEN electric fuel pump, but have read of rig where PO had piped GEN fuel line into main engine return line so GEN would ONLY run when main engine running. Should be piped to separate 3rd pickup line that only goes down to 1/4-tank and then sucks air so GEN does not leave you stranded. Has GEN ever run properly during your ownership? 4000 is a size, not a model, if a KY/similar, you can read codes that help diagnose. LOW fuel or bad Pump will give a 36 UNCOMMANDED SHUTDOWN.

 

[SylverSprings]

Brands new rig. Running the main engine or not, now we only get a few minutes of run from the generator. It is a 4KY - 26100R. We get 3 light flashes after it dies.

 

[Chuck v]

Have you checked the oil level in the generator? Many of the Onan units have a low oil shut down feature...

 

[George and Kim]

Brands new rig. Running the main engine or not, now we only get a few minutes of run from the generator. It is a 4KY - 26100R. We get 3 light flashes after it dies.

 

[SylverSprings]

Maybe main engine run not related, issue is (usually) a bad GEN electric fuel pump, but have read of rig where PO had piped GEN fuel line into main engine return line so GEN would ONLY run when main engine running. Should be piped to separate 3rd pickup line that only goes down to 1/4-tank and then sucks air so GEN does not leave you stranded. Has GEN ever run properly during your ownership? 4000 is a size, not a model, if a KY/similar, you can read codes that help diagnose. LOW fuel or bad Pump will give a 36 UNCOMMANDED SHUTDOWN.

Thanks so much for the helpful advice. But I finally got things going my way. Evidently the coach had set up too long at the dealership and ethanol gas gummed up the generator’s carb.
With a little help from Seafoam and multiple short runs, everything is clear and functioning.

I plan to install a shut off valve to prevent future heartaches.

Thanks again

 

[dramey]

We don't have ethanol gas in Alaska.