Gen fuel supply issue

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Well-known member
Jul 26, 2012
Overgaard, AZ
I've had my '98 Bounder for over a year and never had any gen issues until now. It is a 5500 Onan.
I run it every 2 weeks with a load. I changed oil and filter in the summer. MH gas tank is full.

About a month ago, the gen would not start.

I removed the line to fuel filter and while cranking, nothing came out.
I removed the fuel line to the fuel pump, nothing ran out from the tank line.
I blew into the fuel line to the tank and heard girgling in the tank.

I connected a clear fuel line to the fuel pump and inserted the line in a container with 1/2 gal. of gas.
  While starting the fuel pump began pulling the gas into the line and the gennie cranked shortly afterwards and ran fine.

I had previously replaced the fuel lines on the gen end, and followed the steel line back to the tank.

I'm guessing either the gas hose just outside the tank is bad or the hose? inside the tank.
  Anybody have any experience dealing with the gen tank lines at the tank end?


I would suspect one of 2 possibilities....1.  An air leak between the pump and the tank pick-up or 2. The fuel pump on the generator is getting weak where it can pull from a can but not the pull from the tank.  I would be most suspicious of the line  and pick-up to the fuel tank.
This gen only has 210 hrs on it, but is 14 years old.

I just checked on eBay for fuel pumps and they are in the range of $50-75, so that's not much to fix and/or prevent possible gen pump issues in the near future.

I'll continue to inspect the gas lines near the tank for leaking issues.

It may be the pickuo tube in the tank that is bad. You need to pull a vacuum on the line going to the tank and see if you get fuel coming up to rule out the line. I would use a hand vacuum pump with a brake bleeder attachment to check the line.
I bought a low pressure pump from a auto parts store and replaced the gen-set pump. Used the original wires just spliced in the new pump and a short bit of flex fuel hoses... also had to use a different mounting but it works fine & was way cheaper than the factory pump.
This info is if your fuel line to tank is good and you are looking at a replacement pump.

My guess is that the fuel pickup line has fallen off and into the bottom of your fuel tank.  As gwcowgill suggests (Mighty Vac is a handy RV tool) see if you can manually pull fuel.  If not you've probably found the problem.
Remember I stated:
>>I blew into the fuel line to the tank and heard girgling in the tank.

So it sounds like the tank line is in 'some' gas.

It was 22F this am, hope to do some more testing when it warms up bit.

Thanks for all the suggestions.
Sorry, I forgot about the blowing into the tank.

I had issues this year with my truck engine not pulling fuel adequately.  I wound up replacing all the fuel line between the tanks and the fuel filter housing and found that I had an inline filter that was not sealing very well.  It wasn't leaking but it was pulling just enough air to starve the main fuel filter when I was pulling under load.
I went back to my RV on my lot in a RV park to do some more troubleshooting.

I still had the gas canistor connected, so I cranked up the gen w/o any issues and warmed it up.

I started to go under and check out the fuel lines, but decided to re-connect the tank line(in case it started to flow).
  Just on a whim, I decided to start the gen again. I knew it would probably run for awhile with fuel in the bowl, but it kept running.
  I went inside and turned on both ACs and ran it that way for 20 minutes. No issues.

I need to move the RV a few feet and lower the jacks so I can get under it, so I just left it w/o any more checking.
I still need to get under the tank, to check the gen hose where it leaves the steel line and enters the tank.

Sounds like the Genny fuel pump was unable to pull enough gas (perhaps a leaky line) but once primed it was good to go. Change out any rubber portion of the line 'in case' and you likely will have solved your problem for good.
I agree that youmay have bad rubber lines but don't rule out the steel lines especially if you are where rust could be a problem. Had an old Cadillac once that ran fine until you tried to climb a hill and then it would starve for fuel. Had a pin hole in the steel line.  Hope you find the problem.
Heh, heh,  replaced a few of those in my time, especially up here in the Great White North where salt was used liberally over the roads in winter!!! ;D    Vehicles surely have improved over the years, not too many rusted out wrecks seen around these days.....
Just curious ...did you get the neoprene fuel lines that are resistant to ethanol...there is a difference but I can't remember the SAE number offhand.
I just went to the local auto parts house and asked for 2 feet of gas line of proper size.
Same as I use on my '65 Mustang and '47 Ford 8N tractor.

It was directly behind the counter on a reel.
Fuel and Brake lines have improved over the years as well as the bodies but I still see rust in numerous other places. The old Cadillac was a 1947 and was in West Virginia where salting of the roads was standard procedure.

N7QVU hope that fixes your problem. Keep us posted.
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