Onan CampPower 2500 generator starts, then stops immediately

Sounds like a faulty voltage regulator. Go to flight systems web page. They have a good trouble shooting section, in addition to thier web page, you can call thier techs on the phone and they will walk your way thru the trouble shooting. If you suspect that's it bad. You can send them your old V R and they will test it. They charge for the testing, but if the unit is defective they will apply the charge of testing to a new FS VR (better than the OEM)

I just had the same problem with mine. It would start fine and then when I released the start button it would shut off. I did this several time and then noticed that if I held the start switch, which is a toggle start/stop switch, slightly to the start position it would stay running. After much fiddeling, I figured out that the switch was stuck in the stop position. It was not obvious but I got it to release and the unit has run fine since.

If you have a low oil switch make sure you are setting fairly level don't ask me how I know.

You are experiencing the classic symptoms of a bad oil pressure switch.
Or, it could be a wire to the oil pressure switch.
It is either that, or the generator really is low on oil.

One more thing... some* had an oil level safety. Check the manual to be sure you're checking the oil the proper way**, and that your oil is full.


*I don't now when they quit using this feature, but it shuts the engine down as soon as you let off the switch on the ones that have it.

**You can do it two ways, by screwing the dipstick plug in or by resting it on the edge of the hole. Mine have all been the latter, per the manuals. If yours is too, and you happen to be doing it the wrong way, you're low on oil.

Jim, "I always wanted to be a procrastinator, but never got around to it."

Did you just change/fill your propane tanks? Might be air in the line.

From owning three 2800 Microlites which are similar, I think there's a knockout-type access plug located in the case below the service door. Remove it and the wire boot and you should be able to get a deep plug socket into the plug well. Replace the case plug when done, since it's part of the seal for the cooling air.

(on edit: if the camper structure interferes with access to the plug well, you may have to loosen the mounting bolts and tilt the front up & back.)

But if it's stopping immediately when you release the switch, I doubt it's the spark plug. The small Onans get their ignition voltage from the battery when cranking, but switch over to self-generated voltage once the switch is released. It's likely you have a failed voltage regulator or other issue in the voltage-making process (brushes or rotor/stator).

There's a pretty good step-by-step troubleshooting guide in the factory manual, assuming you have a volt-ohm meter and can use it. Flight Systems has some good info online too, IIRC.

Jim, "Caution! Do not look into laser beam with remaining eye!"

Thanks for the manual Kpack!

Maybe this can help.
Kvd onan service manual

is your battery fully charged, is your converter working
lp is controled by a 12v solenoid valve

also possible that the valve is gummed up and is freezing up
i don't think this is a sparkplug / ignition problem