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Old 03-31-2017, 02:29 PM   #1
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Onan Shutting Down

This happened last fall and has now happened again. My 5500 Onan will run fine if just sitting stationary. Once you get on the road it will only run for anywhere from 15 minutes to 30 minutes before shutting down. I have looked at my fault code and it is of course code 36 (3 blinks and then 6 blinks).

I have read past posts on this forum and did some research online. For my model (2014 chassis/2015 coach - Challenger 37GT) it looks to me like this could possibly be one of three things. A defective fuel pump, inadequate air ventilation to generator compartment, or carb gummed up from lack of use.

I just filled the tank for preparation of heading out on a 7,000 miles plus trip in about 3 weeks. The first thing I am doing is inspecting and probably changing the air cleaner on the Onan and then adding several cans of Sea Foam to the tank.

For those that have had similar experiences with their Onan gen sets, what have you done to correct this situation besides taking it back to dealer or Onan facility?
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Old 03-31-2017, 02:59 PM   #2
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I think you can eliminate the completely defective fuel pump problem: When our fuel pump went out it completely went out. We were using it driving along when it quit never to start again until we got the fuel pump replaced.

If the fuel pump is starving for fuel I don't see how that would be different between driving and not driving.
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Old 04-01-2017, 01:54 AM   #3
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Air + fuel + spark. Pretty simple, yet can be frustrating! Spark is unlikely to be your probem. If your air filter is ok, replace the fuel filter before you take it to a dealer. Seafoam can work wonders!
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Old 04-01-2017, 03:12 AM   #4
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Gotta agree with the SeaFoam. But, I'd take a look at the number of hours on our gennie. If you are getting close to 900 hours or over, I'd look at brushes. Ours went out and we had to replace at about 800 hours. Just suggesting them based on the additional vibration. Also, double check your warranty. Onan (Cummins) has a very comprehensive 1,2,3 year warranty based on when the unit was placed into service.

Just a couple of more ideas to look at.
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Old 04-01-2017, 03:40 AM   #5
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Are you getting any codes when the generator shuts down, if so that can help diagnose the problem.
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Old 04-01-2017, 12:31 PM   #6
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Thanks for quick suggestions. Changing the fuel filter should be fairly simple. Are they available at an auto parts store or do you have to get them from an Onan dealer?


As far as hours on my generator, I haven't looked in the last few weeks but it should be between 50 and 60 hours. When I bought it there were 29 hours on it and the coach had been in service with the original owner for just over 2 years. It only had 3,200 miles on chassis so I suspect original owner was seasonal camper that just parked it somewhere and didn't really travel or use gen set much. I guess that may be working against me as far as gummed up carb or bad fuel filter?


I get the "36" code which is useless as far as telling you exactly what is wrong with it.


My chassis (Ford) 3 year/36,000 mile factory warranty expired in May 2017, so that would indicate that the Onan would have been in service 3 years also in May of 2017. I may investigate to see if it is still covered under original warranty if I can't keep it running. My extended warranty would probably also cover it but I like to "bang my head against the wall" for awhile and fix my own issues first if possible.
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Old 04-01-2017, 01:08 PM   #7
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Joe, you're right, code 36 is kind of a catch all, it means something is wrong, ok but what? Sorry this was no help.

You can try disconnecting the fuel hose, getting a small gas can, and putting a short length of hose in the can, this will tell you if it's a supply problem from the coach tank. After that it's a process of elimination to figure out what's wrong.

On one of my older coaches I had the same problem, turned out to be the coil shorting internally when it got hot, took a while to figure that one out!
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Old 04-02-2017, 02:50 PM   #8
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Joe, you're right, code 36 is kind of a catch all, it means something is wrong, ok but what? Sorry this was no help.

You can try disconnecting the fuel hose, getting a small gas can, and putting a short length of hose in the can, this will tell you if it's a supply problem from the coach tank. After that it's a process of elimination to figure out what's wrong.

On one of my older coaches I had the same problem, turned out to be the coil shorting internally when it got hot, took a while to figure that one out!
I am hoping it doesn't turn out to be anything as hard to find as that! Going to buy more Sea Foam today, not sure 2 cans is enough.
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Old 04-07-2017, 03:17 PM   #9
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Joe, I had a similar problem that drove me nuts. I even replaced the coil, fuel pump and carb where new and the filter was not restricted. I turned out to be air in the fuel line after running the main fuel tank a little too low. I simply pulled the fuel line off the carburetor and put it into a jar while running the fuel pump to purge the line. Worked like a charm after that. Intermittent fuel supply or air in the line can be very frustrating to diagnose.
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Old 04-08-2017, 12:57 AM   #10
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My generator would shut off replaced fuel pump but it would still die sometimes after 30mins the dealer was finally able to figure it out after many attempts it was the vent line for the fuel tank
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Old 04-08-2017, 01:05 AM   #11
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Joe-Fl - when I was having issues I used the spray Sea-Foam then added the gas tank additive. Really fixed it.
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Old 04-08-2017, 03:16 AM   #12
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If It runs fine when sitting, but quits during travel, it would seem to me that there could only be two causes, One, a plugged vent line as above, because two engines are drawing from the same tank, raising the negative pressure, or two, road airflow is disrupting the generators normal airflow and causing an over heating situation. You do have the generator access door in place correct?
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Old 04-08-2017, 12:49 PM   #13
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Thanks for continued suggestions/support. Between getting the house ready to close up for a few months and checking off different maintenance items for the MH, I am working my way back to my generator issue next week.


I will be cleaning or changing air filter, changing fuel filter, inspecting fuel tank vent line, spraying carb with Sea-Foam spray, and dumping about 4 cans of Sea-Foam into my tank.


My side cover is in place on the generator and fits good, never an issue there.


I'm going to have to crawl under the coach to try to locate the fuel tank vent line, possibly around the back end somewhere. Don't recall seeing it. I assume it will be a rubber hose coming from the area of my main fuel tank.
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Old 04-08-2017, 01:01 PM   #14
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The vent hose typically enters the tank right next to the fuel hose to the engine. Both go through the sending unit plate.
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Old 05-13-2017, 05:14 PM   #15
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Prior to getting on the road for our 4 months I never had a chance to blow out the air vent line on my gen set. I located it but just never got back under there to blow it out. Fuel filter looked good as did air filter.

I put enough Sea Foam in my tank to equal about 2 ounces per gallon of gas. The new days prior to taking off I put about 10 hours on the generator under load, of course this was stationary. I had one occasion to use the generator while under way last week. Even though it was only for about 45 minutes it never shut down and worked as it should.

I think the Sea Foam may have possibly done the trick!
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Old 05-14-2017, 01:09 AM   #16
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Sea Foam - great stuff!!
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Old 05-14-2017, 09:46 AM   #17
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Sea Foam - great stuff!!
I second that, use it in everything that burns gas!
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Old 05-14-2017, 01:34 PM   #18
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I was having issues with my Onan 4000. Service tech suggested a new spark plug and Sea Foam. Problem solved. I now use Sea Foam for routine maintenance on all my gas engines. I also added spark plugs to my motorhome spare parts.
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Old 07-13-2017, 02:24 AM   #19
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Generator pump running !!!

On our recent trip, on our 2nd day out, we stopped for the night and heard a noise which sounded like something was running. After some searching we found the pump on the generator was running. We had not used the generator nor started it in a few weeks.
Having tried several attempts to stop it...I finally detached the cluster of wires to the generator.
We returned from our trip a couple days ago and I have not had time to do further checking nor have I plugged in the wires to see if it was just a glitch.

Has anyone had a similar problem or have an idea of what the cause might be?

I checked the Onan Troubleshooting site and found no reference to this problem.

Ron
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Old 07-13-2017, 02:26 AM   #20
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Quote:
Originally Posted by vkb View Post
On our recent trip, on our 2nd day out, we stopped for the night and heard a noise which sounded like something was running. After some searching we found the pump on the generator was running. We had not used the generator nor started it in a few weeks.
Having tried several attempts to stop it...I finally detached the cluster of wires to the generator.
We returned from our trip a couple days ago and I have not had time to do further checking nor have I plugged in the wires to see if it was just a glitch.

Has anyone had a similar problem or have an idea of what the cause might be?

I checked the Onan Troubleshooting site and found no reference to this problem.

Ron
If the fuel pump was running that may indicate that it thought someone was holding down the stop button (e.g. prime). Perhaps you have a short somewhere shorting the stop/prime contact.
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