Onan generator shuts down

[tacgle]

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?

[Community Alumni]

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

[Don_Don]

Avoid guessing.......call Onan.

[sc3283]

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

[Community Alumni]

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.

[C-Leigh_Racing]

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

[wb2ivu]

The above is a perfect example of my fingers and brain refusing to listen to each other...

"It turned out to be the coach batteries. We added the necessary amount of Distilled water and the Generator ran fine."

Um... what did I add the water to? LOL!

I never thought to check the water level in the coach battery's, simply because they were new. (within the year)... So, in Milan Tenn, the Gen stopped working. It was not till we got to a RV repair facility the Tech discovered the water in the battery's had been boiled off. The Tech filled the cells and everything worked well... until we reached Rochester NY... and discovered the water level in the battery's were low again... This is when we discovered the on board battery charger was over charging them...

Hope this clarifies things...

Chris

[Community Alumni]

Onan 5500 was actually starting by itself in cold weather storage when I turned the battery cut-offs back on. It would also stop by itself after a different run times, sometimes 15 minutes, sometimes 2 hours. Turned out to be a faulty start switch on the genny itself (not the on board dash switch).

Also, sometimes mine would suddenly stop on occasion when a change in load occurred, this was attributed to dirty slip rings after long storage/non-used periods. It woul fix itself (clean up) after 2-3 of these stopping episodes.

[WyoTraveler]

I'm parked & over 90 degrees. I openen the door to the generator compartment & the generator ran for 6 hours. No problems. Vehicle engine was off. Now I think it is a bad sensor. Shuts it down & throws bad code 36.

[wb2ivu]

We had a similar problem with our Bounder. It turned out to be the coach batteries. We added the necessary amount of Distilled water and the Generator ran fine. However, that was not the only issue.. it seems the Converter / Battery charger had lost its ability to detect a over charge mode... So the cycle begins The Gen., would run the charger which actually over charged the coach batteries, and boiled off the water in the batteries, causing the gen, to run hot and go into a shut down mode.. The reason I throw out this as a cause is we have our gen serviced every 4 months, with include all filters.. I was fairly confident it was not a fuel problem causing the Gen to act wacky

[CloudDriver]

Several years back I had the same problem with the Onan Microquiet 4KY generator in our MH. The generator would run for 15-20 minutes, then surge like a lawn mower does when it runs out of gas and shut down. After this happened, the generator would crank OK but wouldn't restart. I discovered that if I waited for 1/2 hour or so, the generator would start and run for another 15-20 minutes before surging and quitting.

Our generator has a "prime" function on the start rocker switch at the generator. This function runs the fuel pump without cranking the starter, which allowed me to hear whether the fuel pump was running. I found that if I tried the prime right after the generator shut down by itself, there was no buzzing sound from the fuel pump. A 1/2 hour later, using prime would give me the normal sound from the pump. I figured that the pump must be heating up and seizing after running for a short while.

Replaced the fuel pump and no more problems since. Replaced the fuel filter while I was at it.

[WyoTraveler]

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.

[Jim]

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

[RedG]

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.

[Sloop_Smitten]

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.