Onan Generator stalls after oil/filter change

[dawg6]

Just realized there are two more oil pressure sensors, on the engine body. Will check those next.

[dawg6]

According the parts manual, for the other two oil pressure sensors, one is supposed to close at 14 lbs decreasing, and it is open while engine is off and while running, which I assume is correct. The other is supposed to close at 5 lbs increasing and it is open while off and closed while running, which I assume is also correct.

[Pascal]

Again different models but on ours the mechanical fuel pump is before the secondary. If that s the case you could loosen up the fuel line exiting the filter, power up the pump to make sure fuel is coming out.

Not sure how an electric pump will work on a gen without a preheat button. With a preheat or run switch the pump kicks in so you can prime. If your Onan only has a start position you can’t use it to bleed.

[dawg6]

According to the owner's manual, I should hold the start/stop button in the stop position for about 10 seconds to pre-heat the engine. Not sure if that also activates the electrical fuel pump or not.

I guess I can change fuel filter to find out. I was hoping to avoid that until last resort (since after that, if it stalls out I won't know if the engine is primed or not). But I think I've checked everything else it could possibly be. It sure sounds like a fuel problem: maybe fuel filter is clogged or the fuel pump is failing. Either way, I guess I'm at the point where I need to take that filter off.

[Pascal]

I change the secondaries (and primaries) at every oil change. always.

The pump should be wired to the preheat circuit. Easy to check. Press the stop switch and hear/feel the pump

[northshoreone]

Does it have a overheat sensor? My 1996 20k did and it was bad, doing the same thing yours is doing. Simple fix if that’s what it is.

[northshoreone]

If I remember correctly it was the two wire sensor in your pic

[dawg6]

Well, I guess the simplest solution really was the right solution. Replaced the secondary filter and now it purrs like a kitten again. Maybe when I changed the Racor filter some debris got dislodged and stuck in the secondary.

BTW, the off button didn't engage the fuel pump. It only turned on when I held the start button. When the engine stalled I could even hear the fuel pump "clicking" until I pressed off (now I know what the clicking sound was).

Anyway, I like the advice of always changing both when I do oil changes. Will add that to my check list from now on.

Time to go change the one on the other generator as well and order some more spares.

Thanks everyone! In the process I learned a lot more about my generator and troubleshooting.

[Pascal]

Glad you got it! A little odd that the dirty secondary would shut down the genny so quickly with no load but... it s a boat!!

[Westfield 11]

Do both fuel filters really need to be changed every 100hrs? IIRC, that’s the oil change interval for the MDL4 of that vintage…..