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Old 08-19-2010, 02:18 PM   #1
Join Date: Mar 2010
Posts: 56
Unhappy Onan Gen starts, then stops and won't restart

I have a 5.5HGJAB-1038C generator in my 2005 Pace Arrow. While the rig is garaged, I try to start the generator and it starts, but only runs for 1-3 minutes before quitting. The fuel tank in the rig is near full. I crawled underneath and disconnected the fuel line from the filter that's attached to the fuel pump. Nothing. No gas comes out. I blew compressed air into the fuel line, and the fuel began flowing. I reattached the fuel line and everything worked well (gen ran for 45 minutes). A few days later, the gen started up but once again quit after 1-3 minutes. I thought I had a fuel pump issue, so I bought and installed a new fuel pump and 2 new filters ($120...ouch!). I once again blew compressed air into the fuel line and heard the bubbles coming into the fuel tank. I reconnected and everything ran fine. Until a few days later, when I once again had the same issue with the same symptoms. It appears there is some sort of blockage somewhere between the fuel tank pick-up and the generator fuel pump. I need some help.
Additional info: When the gen stops, the light on the start button blinks 3 times. When I hit the Stop button to get the code, I get no code.

Any ideas? Does this generator have anything in the fuel line, inside or outside of the tank, that prevents fuel from flowing under certain conditions?


2005 Pace Arrow 37C, our 3rd Fleetwood.
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Old 08-21-2010, 01:36 AM   #2
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kgarvey, Is there a way you can SAFELY ... let me repeat that S A F E L Y temporarily disconnect the existing fuel line at the point where it enters the genset, CAP IT OFF SECURELY and provide a TEMPORARY fuel source from a fuel can just to rule out fuel starvation issues.

Be sure that you have the temporary fuel supply at the same vertical level to replicate the "lift" or provide the gravity flow under which it normally operates.

Since you have already replaced the fuel pump and filters, you have elimnated the most likely causes. However, if it is a long run from the gas tank to the genset, you may have an internal fuel pump in the tank... or a booster pump somewhere along the line... so verify that.

By providing a temporary fuel source, you will perhaps be able to narrow the problem down... i.e., if your genset works ok with the temporary supply... then work backwards to the main tank.

Sometimes fuel lines can delaminate internally and there is no outward indication. As the fuel pump runs and pulls fuel, the line collapses slowly. This can provide the symptoms you describe. Even if a fuel pump "pushes" a line, the pressure can cause an any internal loose layers inside the fuel to ripple and dam up the line... and thus starve the genset... same symptoms as you describe.

Remember also that the "pick up" for the generator is a bit higher in the fuel tank to avoid leaving you stranded in the deep woods. You must verify that the pick up is not only is clear (the bubbles in the tank as you blew compressed air)... but verify WHAT it is picking up... is there gunk that resettles after a while or exessive water (doubtful, but possible) and the pick up sucks it up?

Again, please proceed in a very SAFE manner to avoid causing a fire. You MUST be certain that you do not create a situation where an internal fuel pump is delivering fuel and it spills... cap off line, place it in a 5 gal. pail and have someone monitor it while you check this out so you can shut it down if it goes "sideways" on you.

Suggest also you take the coach out of any building or enclosure and have a suitable fire extenguisher handy. Lot's of people believe that gasoline is FLAMMABLE. I'm one of them.

Please provide feedback one way or other ... we learn a lot when we know what does and does not work.
Good luck and BE SAFE!
All the best,

Jim and Fran in Central Florida
1989 Country Coach Sedona Mark V
Turbocharged Detroit Diesel 8.2L "Fuel Pincher"
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Old 08-21-2010, 06:15 AM   #3
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Had the same trouble a couple of years ago. Fuel line had developed some cracks a few feet before it entered the fuel tank and would suck air. Had to drop tank to replace line. Has run fine since replacement.
Found crack by blowing back into disconnected fuel line then capping. In a short time fuel oozed out. MH was 5 years old at the time. Good luck


PS This happend to me on a 1977 Ford car 25 years ago should have known.
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Old 08-23-2010, 01:48 PM   #4
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localized the issue

Thanks for the suggestions and feedback. I first did the fuel pump test by disconnecting the fuel line at the carburator filter and putting that end of the fuel line in a jar. I disconnected the existing fuel line at the fuel pump and replaced it with a 3' piece of fuel line with the loose end in a container of gas. I ran the prime (holding down the stop button) and sure enough, gas flowed into the jar. Fuel pump is not the issue.
Next test is the leak test. I reconnected the existing fuel line at the carburator. The other existing line at the fuel pump I left disconnected, but plugged the end of it solidly. I set my air compressor to the lowest setting. I used rags around the regular RV fuel tank filler and fed compressed air into the fuel tank (no more than 20 psi or damage might result). I crawled under the tank and within seconds began to smell gasoline. Then, saw it running from the top of the tank down the sides of the tank. I turned off the compressor and removed the line from the RV fuel filler. The issued is now localized to the top of the fuel tank, either the piece of flexible fuel line up there, or the pass through into the tank. The tank will have to be dropped to fix this. But, at least the diagnostics are done so the labor costs won't include diagnostics.

Thanks for the suggestions. Hope this information helps someone who experiences these same symptoms.

2005 Pace Arrow 37C, our 3rd Fleetwood.
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Old 08-25-2010, 08:45 PM   #5
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Had the exact same problem a couple weeks back with my Onan while on vacation. Took it into Camping World and they diagnosed it as a dirty carburator which is very common for them. Was a $150 fix.
99 Fleetwood Southwind 32V (Class-A)

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Old 08-31-2010, 08:17 PM   #6
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Had the same problem 2 wks ago. took the bowl from the bottom of the carb off, cleaned it and then sprayed B12 carb cleaner , put it back together, runs great
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Old 08-31-2010, 10:13 PM   #7
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94 Brave. Onan 5.0 is having similar problems. Runs 1-3 minutes. Removed filter and there is no fuel. Any idea what pressure the fuel pump ranges? I have a non-Onan electric low pressure pump. Can I swap it out for the Onan pump? I will do the tests mentioned to rule out fuel line leak.
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Old 09-01-2010, 05:34 PM   #8
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Onan Gen Stop Running

FYI, on a diesel Onan Generator the oil level is critical. Mine would shut off after a few minutes and I couldn't understand why!!! Spoke to Onan and they asked about the oil level and I said "Fine, only a 1/2 qt low".... silly me!!!
They nicely asked me to top it off since it only holds about 3 qts and a safety shutoff switch is designed to be sure it has enough oil. Topped off only a 1/2 qt difference and it's been fine ever since!!
I know the discussion is gas fuel, but.......
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Old 09-02-2010, 08:42 AM   #9
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Careful replacing the pump. Onan generators use a low pressure pump and won't work (or for long) on a higher pressure.
On an older rig, I'd vote for the line cracked and leaking under vacuum of the pump (ask me how I learned this). Unless its in a very hot location a newer rig should not have hose problems (check for exhaust close to line (can also cause vapor lock).
There are several cutoff switches on an Onan generator; these can include oil level, temperature, low speed, and probably some I've forgotten.
Ernie n Tara

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Old 09-08-2010, 06:40 PM   #10
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I have the same problem on my 2003 FW Southwind, all this started when we was dry camping and running the genset till the gas tank went to 1/4 and the genset shut off, that is whene I started having this problem. I think I will replace the rubber gas line first before I venture to something I know nothing about. But I have to amit everyone has provided out standing information. Thanks
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Old 09-09-2010, 10:25 AM   #11
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Here's a summary for this issue.


1. Check fuel level in gas tank. To be safe, it should be 1/2 full or more to rule out the fuel being too low in the tank for the genset fuel pick up tube.
2. Check the oil level. It, too, must be near full.
3. Check the failure code. If the genset was running, and then quit, there should be a light on the genset start switch (the one on the genset itself) that is blinking 3 times, then pauses, then blinks again. Depress the switch in the STOP direction and release. The blinking should then represent the 2 digit error code; the first set of blinks is the first digit, the second set of blinks is the second digit. Consult you manual for the meaning of the code.
4. Carb and Pump test: Detach the fuel line at the carburator. Place the loose end into a glass or plastic container. Depress and hold down the STOP switch to activate the pump and primer. If fuel flows into the container, the problem is not fuel flow; it's probably a carburator issue. Listen for the pump while priming. If it makes a rapid clicking sound, it is running dry. It should make a softer whirring sound if it's getting fuel.
5. Pump Test. Reattach the fuel line to the carb. Attach any kind of a choking device to the fuel line on the gas tank side of the pump to prevent fuel flow. Have a container ready. Detach fuel line from the pump and place end in the container. Slowly release the choke on the fuel line and see if fuel flows into container. If so, choke it off; you have fuel coming from the tank. Problem is the pump. Replace with LIKE KIND (low pressure).
6. Leak Test. Rechoke the fuel line but leave it detached from the pump (step 5). Using rags to prevent air from escaping, put about 10-12 psi of air pressure into fuel tank at the fuel filler. BE CAREFUL! DON'T USE TOO MUCH PRESSURE. YOU ONLY NEED ENOUGH TO PUSH FUEL UP THE PICK UP TUBE AND INTO THE GENSET FUEL LINE. Check underneath fuel tank for leaks. You'll smell gas if it's leaking. If leaking, problem is with the fuel line on top of fuel tank or the fuel pick up pass through in the fuel tank. Take out your wallet.

This summary is only of my experience, which is casual as an RV owner. I'm not a technician. Techs may have more savy or even safer procedures.

Be safe. And Thanks for the input, everyone.
2005 Pace Arrow 37C, our 3rd Fleetwood.
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Old 09-09-2010, 11:43 AM   #12
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Originally Posted by Downsizer View Post
FYI, on a diesel Onan Generator the oil level is critical. Mine would shut off after a few minutes and I couldn't understand why!!! Spoke to Onan and they asked about the oil level and I said "Fine, only a 1/2 qt low".... silly me!!!
They nicely asked me to top it off since it only holds about 3 qts and a safety shutoff switch is designed to be sure it has enough oil. Topped off only a 1/2 qt difference and it's been fine ever since!!
I know the discussion is gas fuel, but.......
Thanks for your input. I always run my a little low. Sometimes it will stall and other times run just fine. Never could figure out why. I think you have solved the mystery.

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