Onan generator shutting down after releasing start button

[Lyman713]

Hi! I have a 2013 class C with an onan 4KY generator (series P). It only has about 200 hours on it. It shut down one day (actually after being on only for about an hour after Hurricane Ian) and then when starting, it turns over great, but shuts down right after releasing the start button.

When I hold the button, I get a four blinking light code.

I disconnected the inside switch with no luck.

The odd thing is that, about 2 months later, I tried starting it, and it started right up and ran (no load) for 5 minutes and I manually shut it off. I tried again a couple of weeks later, and it started right up again.

I tried last week, and back to the issue of shutting down right after releasing the start button.

It is a manual transfer, so I have a 30 amp outlet I plug my RV cord into when I want to use the generator. I checked for AC voltage at this plug and get about 20 VAC.

Any thoughts? I initially thought brushes, but having it start up in between issues seems like it might not be (and also the low hours).

The RV is a bit low on fuel (about 1/4 tank) but I would think that a low fuel situation would not fire the generator to run initially anyway. (Unless there is some sort of electronic fuel sensor on the genset that faults the control board?? - I always thought the fuel pick up was just higher in the tank).

The control board it buried under the start relay, and I haven't tried taking out P1 and looking into that yet.

Any thoughts on accessing the control board on this model? I'm trying not to have to figure out how to get the generator out of the RV and work on it while still mounted.

I don't believe there is any oil sensor (the oil is full - recently changed about 20 run hours ago), but if you believe otherwise, please let me know!!

Thanks in advance for any insights or help.

[wa8yxm]

It could have been a whole lot more expensive....

But that's a different error code.

And before you ask... NO it was not MY generator.. (My Neighbor's at an event) Showed the code for "Low battery/cranking speed too slow" even though the ears said otherwise (Calibrated ears don't you know)

Turned out to be no AC out from generator (Brushes/commutator rings)

Thankfuly the party was parked next to the only two working (part time)(30 amp outlets on the desert (MY RV had a pair of TT-30 outlets) so They ate off my Onan... That's not why I put 'em in but hey. worked when it had to.

[MNtundraRet]

Thank you for letting us know it was the control board.
I needed to replace the board once.

[Lyman713]

Update from OP - took a chance and got a new control board from flight systems. Worked great! Ran awhile under 80% load perfectly.

Thanks to all for the insights.

[bounder39zman]

Mr Wizard's info is pretty much correct. If you are getting 20vac at 30amp gen receptacle, then most likely a "field" problem. Even at only 200 hrs, the field brushes might be sticking in the holder, or the slip rings are oxidized or dirty. possibly a control board going bad, as the field (voltage regulation) is part of the control board. Unfortunately, brushes/slip rings are not easily accessible, as they are located behind fan/flywheel assembly. there are troubleshooting procedures to determine problem, but some specialized test equipment needed. BTW, no low oil level switch is used on this spec 4KY.

[MrWizard]

The brushes are for the field winding in the rotor, a stuck or dirty brush can mean no field current which equals low or no output voltage/power, a failed control board also does this,brush problems are more likely to be weather condition intermittent, than control board problem,
Check the brushes and the wiring, dirt or corrosion is a possibility

[MNtundraRet]

Have you checked connections to the control board? The board may need to be replaced.

[Grit_dog]

Maybe not the issue but worth mentioning, the ecu or control board on the one Onan I had was NOT waterproof.
Basically brand new generator I washed the dust n dirt out of it and shorted out the board. Temporarily thank goodness.
If it got wet it could be the issue.

[Lyman713]

Thanks for the replies. I'm saying it's not low fuel or other issues. It runs great, so long as I'm pressing the start button. (which bypasses the control board from shutting down the unit). So, I'm saying not fuel, carb, etc., as the engine side seems to run great (starts right away and I do try priming when I haven't run it that day).

[wa8yxm]

https://thecampingadvisor.com/onan-generator-fault-codes/

[midnightsadie]

I,ve hears this problem before go put fuel in the rv and see if it goes away gauges are not to be trusted.

[wra]

I had a similar problem. The problem was the fuel shut off solenoid on the carb. It got stuck in the shut off position. Clean or replace it and it should be good again.

Having a low RV fuel tank could be a problem too. The gen gets its gas from the RV tank. The pipe that the gen gets the fuel does not go to the bottom of the RV tank. This keeps the RV from running out of gas by the generator use. There should be enough gas left to get to a gas station.

[Bobbo]

When I had an ONAN in my previous MH, the ONAN manual said to exercise it for 2 hours once a month under 50% load.

[MNtundraRet]

Did you prime the generator before trying to start it.
It sometimes takes a few times to get enough fuel to start the engine.

By the way, you should always run the generator about an hour to dry out all components. There is a saying for generators: "Use it or lose it.".

[bmwbob]

Ours will do that also IF either the oil level is low or the gas tank is not nearly full.
Since becoming aware of those issues and keeping things topped off, I’ve had no problems.
Bob