I have an Onan 4000 microquiet model #4KYFA26100K. It will start and run and generate power. BUT, it randomly shuts down. Might be after ten minutes or two hours or 10 hours. Lately the best I can get is an hour or so, usually less. It has 2000 hrs on unit. I have changed fuel pump/ filters(twice), new fuel lines from tank. New spark plug and air filter. Oil is fresh and full. When unit shuts down, I've noticed that there is often not power to fuel pump until it's cooled down. Not always the case, but often. The Gen is located in a compartment, but I've experienced this in cool weather as well as hot. Unit does get adequate airflow and since it has 2000 hours, it's obviously run quite well in this space for sometime. I don't think it's the coil, since a faulty coil or coil wire shouldn't cause a no power to fuel pump issue at restart. I'm leaning toward the control board being the issue, just want some feedback before I invest $300 for a new board from Flight systems

Is there fuel in the float bowl of the carburetor when it shuts down?Chum lee

Does your generator have auto shut down for over temp or low oil pressure? If so, one of your sensors may be the cause. With the hours, these seem to be the first to give problems.

It does have fuel in carb bowl. To the best of my knowledge the K series units don't have any oil sensors. Not sure about temp sensors. The fault code is 36. Which translates as Unexplained Shutdown. Thanks to Onan for that real helpful diagnostic code...

¿Does not have low oil protection shutdown? Ya might wanna continue to probe...

stick a fan out there and see if your over heating, gotta start some where.

Onan 4000 microquiet randomly shutting down | Good Sam Community

11 Replies

TEXAS
Explorer
Apr 10, 2017
Your unit doesn't have a low oil sensor. That was dropped at spec B you have a spec K unit. The code you are getting is shutdown but no idea why. I would go over the connections. Clean and make sure the connections are good.
j-d
Explorer II
Apr 09, 2017
OP - Pretty (99 pct)sure you're right about the low oil signal deleted from the newer (many years before yours) 4KY's.

They're splash lubed like a mower, so there's no pressure to monitor and the oil sump's agitated all the time so no way to monitor the level. FYI this is why 4KY also does not have an oil filter: No way to pump oil through one. ONAN had more problems with false oil errors with the sensor so they deleted it and threw the burden on us to check oil more often. That said, there isn't much to go wrong with a 4KY's "oiling system" since there really isn't one.

DO check the oil often. That's an air-cooled engine running 3600 RPM so it's rough on oil. We had a rash of 4KY engine failures a few years ago that seemed to be mostly low oil.
JaxDad
Explorer III
Apr 09, 2017
Those units use externally excited coils, so voltage out is in direct relationship to the voltage input.

If you give it 12 volts, you will get 120 volts. If however you only have 9 volts in you will only get 90 volts out. Since that is an unsafe output the Onan will shut down for safety.

Check & clean all your connections, including the grounds.

All it takes is a funky connection to cause a momentary drop in voltage and you will see exactly your symptoms.
DrewE
Explorer II
Apr 09, 2017
It might be a useful exercise to check that all the wiring harnesses and connectors are good and tight and clean. Intermittent electrical connections can be very tricky to track down and cause all sorts of weird symptoms that aren't particularly repeatable.
MEXICOWANDERER
Explorer
Apr 09, 2017
Call a lawn and garden tractor repair place for accurate info. No doubt there are some sources out there who swear some cars do not have dipsticks and have permanently sealed cooling systems.
Jdfire12
Explorer
Apr 09, 2017
All that I've read on this series of gens said that Onan discontinued oil level/ oil pressure sensors. I can't find any drawing or posts that show location of an oil sensor. You would think a $3000 unit would have some type of oil sensor. If I'm wrong I'd sure wish someone would provide the location of it. I've suspected it as a culprit
midnightsadie
Explorer II
Apr 08, 2017
stick a fan out there and see if your over heating, gotta start some where.
MEXICOWANDERER
Explorer
Apr 08, 2017
¿Does not have low oil protection shutdown? Ya might wanna continue to probe...
Jdfire12
Explorer
Apr 08, 2017
It does have fuel in carb bowl. To the best of my knowledge the K series units don't have any oil sensors. Not sure about temp sensors. The fault code is 36. Which translates as Unexplained Shutdown. Thanks to Onan for that real helpful diagnostic code...
drmopar
Explorer
Apr 08, 2017
Does your generator have auto shut down for over temp or low oil pressure? If so, one of your sensors may be the cause. With the hours, these seem to be the first to give problems.