Onan generator shuts off after 45 minutes.

Stump Jumper · 08-05-2010, 07:49 AM

My 2000 Bounder has a 5500 watt Onan generator. It will run fine forever when the motorhome is stationary. When we are on the road, it will run for about 45 minutes and then shut off. It is then very hard to get restarted. If it restarts, it will run again for a few minutes and then shut off again. I thought at first that it might be overheating, but that doesn't make sense if it will run continuously while stationary. My second thought is that it is running out of gas, possibly because of a vacuum problem when the coach motor is running. I see no change in performance with the coach motor when this happens. Oil and air filter are fine. Thoughts?

Fossilhog · 08-05-2010, 07:55 AM

Quote:

Originally Posted by Stump Jumper

My 2000 Bounder has a 5500 watt Onan generator. It will run fine forever when the motorhome is stationary. When we are on the road, it will run for about 45 minutes and then shut off. It is then very hard to get restarted. If it restarts, it will run again for a few minutes and then shut off again. I thought at first that it might be overheating, but that doesn't make sense if it will run continuously while stationary. My second thought is that it is running out of gas, possibly because of a vacuum problem when the coach motor is running. I see no change in performance with the coach motor when this happens. Oil and air filter are fine. Thoughts?

Are you getting a fault code?

**RJay** · 08-05-2010, 08:14 AM

You don't mention how much fuel you have in the tank at the time the generator quits but it could be the sloshing of fuel while driving put the level of fuel below the pickup tube for the generator and you suck air. It also could explain why it is hard starting since you now have air in the line. The pick up tube could also be a little higher in the tank than normal which makes the problem more pronounced.

InPursuit · 08-05-2010, 08:48 AM

with mid summer heat (and poor ventilation) it could be simple vapor lock

Stump Jumper · 08-05-2010, 10:56 AM

To answer some of the replies...It will do it no matter the fuel level. I am aware that most motorhomes will not allow generator operation if the tank is below 1/4. It will even do it on flat highways with a full tank. Also, I am not aware of any fault codes. How do I check those?

Stump Jumper · 08-05-2010, 10:59 AM

Could it possibly be something with the gas cap not allowing enough ventilation, causing vaporlock?

thepratts · 08-05-2010, 11:02 AM

Had same symptoms with a bad fuel pump. Replaced it and all was OK. It was also an Onan 5500. It is not hard to replace, it is under the generator. It looks almost like a filter but has two wire going into it.

Ron2 · 08-05-2010, 03:26 PM

How about oil level, checked it? I have an older Onan (1996) in my RV and was driving mountain roads with the generator on to run the A/C and it generator would die and I would have to restart it. It did this several times then I noticed it would only die while I was on an incline then it dawned on me that there is a low oil switch that shuts the generator down when it reaches a low oil level. On the next stop I checked the level and sure enough it was low, added oil and it ran fine the rest of the trip.
Ron

Ron2 · 08-05-2010, 03:28 PM

Opps, I just read your post again and noticed that you indicated that "oil and filter are fine". Sorry.
Ron

Stump Jumper · 08-05-2010, 03:37 PM

No problem, I appreciate any help that I can get on this one. We will be traveling in the heat this Sunday and I will need the generator to power the roof air in addition to the dash a/c.

AFChap · 08-06-2010, 07:49 AM

Fault code will be a sequence of "blinks" of the lighted start switch immediately after an unplanned shut-down. It helps if you read about them in the manual first o you understand what kinds of sequences to look for.

scoutmstr · 08-06-2010, 11:02 AM

If you have had this problem since you owned the coach, you might consider heat from the engine muffler system causing an overheat problem with the generator fuel line and vapor lock. Check the fuel line to the gen and it's closenest to a heat source created with the engine running. Try insulating the gen gas line.

Stump Jumper · 08-11-2010, 11:43 AM

Well, on the 600 mile trip home from our vacation, I loosened the gas cap on the motorhome and tried running the generator while traveling that way. Strangely enough, the generator ran smoothly the whole time and did not shut off. Do you think that I just need a new gas cap or is this a symptom of a weak fuel pump like someone had earlier suggested?