I have an Onan Marquis 5500 Generator on my 33R, 2002 Fleetwood Bounder that runs for approximately twenty minutes and then randomly revs up and down, then shuts off. It seems to last a little longer if the motor home is in motion and/or in heat. I am aware of the ¼ gasoline tank tank automatic shut off and have made sure the tank was full. I have also changed the oil to the recommended higher viscosity of 15W 45, replaced the air filter, removed the oil pressure sensor indicator, and even loosened the gas tank cap, because I had read of vapor locks. None of this has worked. I am not sure if I have a fuel delivery or electronic problem. The Fault code is 36, which means, “Engine Stopped without Command” (really, it says that!). I have even called Onan and they aren’t sure what it is. Has anyone else experienced this? Suggestions?

Lots of people that have this 20 minute shut down problem change the fuel filter right off. If that doesn't do it, then disconnect the fuel line and put it into a can of gas. If the rubber fuel line on top of the fuel tank is leaking, drawing air, that can give your symptom. Why it can repeatedly take 20 minutes for the problem to show up is a mystery to me. Or I can't remember what others have said about it.

Why it can repeatedly take 20 minutes for the problem to show up is a mystery to me. Here is why I think it takes 10 – 20 minutes for generators to shut down when they have a clogged filter or cracked fuel hose. The carburetor has a carb bowl that contains a few ounces of gas. The generator feeds off the fuel in the carburetor bowl and if you cut the fuel supply the fuel in the bowl will allow the generator engine to run for a few minutes.. The cracked fuel line, or clogged filter, doesn’t allow enough fuel to flow into the bowl to compensate for the amount of fuel the generator engine needs to run. It is providing some gas, just a reduced amount. After about 10 – 20 minutes (dependent on how clogged the fuel filter is or the amount of air being dragged into the fuel line) the bowl runs low enough to starve the generator’s engine. Hence you are good for about 10 – 20 minutes. Some ideas on how to distinguish if your fuel line, fuel filter or fuel pump is the problem would be of great benefit to many on the forum.

I agree. Sure sounds like time for a new fuel filter to me. A lot of times when an engine is running out of gas, it leans out and runs a little faster or revs up and down until it dies.

Excellent eval Sloop Smitten. Now, if I can only remember that for more then a few hours I'll be doing well.

Mine ran for over 2 hours again this morning before it shut down. Once cooling for 30 min then it would only run 15 min. I suspect vapor lock, bad pump or filter. Mine is still under warranty so will see what they say. It threw code 36 which is no fuel.

Onan generator shuts down | Good Sam Community

C-Leigh_Racing
Explorer
Jul 03, 2013
On what year models do they have the "prime function" on the gen start switch. Does the rocker switch have like a three step feel, how will you know ?.
Thanks, Neil
Community Alumni
Jul 03, 2013
C-Leigh Racing wrote:
On what year models do they have the "prime function" on the gen start switch. Does the rocker switch have like a three step feel, how will you know ?.
Thanks, Neil

On my Onan 5500 (2008), both the in dash and 'on unit' toggle on/off switches have integral primer lights. Hold the switch down and the light comes on indication the pump is priming. I usually prime mine about 10 seconds if it has sat for a month. If I've been using it regularly, it doesn't need priming.

Personally I'd rather have a choke like on my Honda 2000 I use around the house and the Honda 3500 we use in the race hauler. They don't get too much use (long intervals off) but they sit with Sta-Bil in them and are never an issue. I wish the Onan's would be that way.
sc3283
Explorer
Jul 04, 2013
Packer, your Onan has a choke...it is automatic....the "prime" feature on the rocker switch just activates the fuel pump to ensure fuel in the line and in the carb bowl..well let me rephrase...my 2006, 5500w Onan has a choke and primer feature...I'd bet yours is the same
Don_Don
Explorer
Jul 04, 2013
Avoid guessing.......call Onan.
Community Alumni
Jul 04, 2013
sc3283 wrote:
Packer, your Onan has a choke...it is automatic....the "prime" feature on the rocker switch just activates the fuel pump to ensure fuel in the line and in the carb bowl..well let me rephrase...my 2006, 5500w Onan has a choke and primer feature...I'd bet yours is the same

Mine is the same but what I really would like is a manual mechanical choke; I'm an old school 'hand over the carburetor ' guy ! :B

... Eric

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Onan generator shuts down

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