Generator Fuel Leaks and Safety Issues

[cbr46]

Re: Onan Marquis 5500 on a 2002 Ford F53 chassis

A month ago there was fuel leaking at the fuel pump - the rubber fuel line had gotten old (14 years old) and was cracking around the hose clamp, which was one of those worm screw types around the line.

I highly recommend NOT using this type!
No problem. New fuel line, new clamp, good as new.

Then on the next trip the generator started cutting off after an hour or so, usually with driving and running the roof air in the July heat. A buddy said the fuel pump was collapsing the fuel line between generator and fuel tank based on his experience but after researching threads here on RV.net I decided to replace the fuel pump.

Last Friday I saw the back half of a nice looking Class A in full flames on I-75 near Macon GA. The part that was engulfed was toward the rear, about where the generator would be. That kind of thing can make you nervous . . . . .

So Tuesday I replaced the generator fuel pump (Onan Marquis 5500) with an Airtex unit through Amazon this week. Airtex is the OEM supplier for Cummins / Onan.
https://www.amazon.com/gp/product/B0076D5OI2

During the repair I noticed a very slight drip from the carburetor float bowl drain port. Very slight, but I was able to tight the drain screw 1/16 - 1/8 of a turn. No more drip. The drain screw had loosened by itself and was dropping fuel onto the engine plate but with all the cooling air blowing around I'm sure vapors were airborne as well. Very bad. I also put a drain hose on the port. Good idea.

Then on testing I noticed the fuel filter at the carb (original design has 2) was leaking around the body of the filter.

I always use a wrench on the "big nut" and never torque the filter on the body, (because I've done this before causing one to leak) yet it was loose enough to seep past the seam between body and nut. HAS ANYONE ELSE EXPERIENCED THIS?

At some point Onan recommended removing this filter, relying only on the filter between pump and tank, but I didn't have the hardware to swap it out. Maybe the fuel pump 4 psi causes them to leak?

I've fixed 3 generator fuel leaks in a month's time and witnessed a horrific fire that might have originated from a generator. AM I GETTING PARANOID?

Just check your generators . . . . PLEASE!

Best,
- bob

[Gjac]

I had a slight leak in my fuel line going into carb. I took me awhile to see the problem but it turned out to be a crack in the flare at the end of the tube. I had to cut off the cracked end and reflare it to get it to seal again. Another time when I removed the cover of the genset to replace a coil I found nests of dried grass and acorns packed under the cover. Both of these could have started a fire and were not obvious.

[wildmanbaker]

Thanks Bob, I know a lot of people hate the spring type clamps, but they do a fair job at sealing.

[bounder39zman]

Onan released service bulletin number of years ago covering these concerns. The worm gear type clamps should not be used, instead use what is called "fuel injection hose" clamp, pictured in previous post.
The fuel filters at carb. is considered redundant to filter at pump, and they were prone to leakage. Onan made a fitting available to replace the filter at carb, p/n A029S253. They also have a better filter, p/n 149-2341-01 to use at fuel pump. This filter has larger diameter than previous filter, and is difficult to install at carb....so replacement fitting should be used here. The newer units, and replacement carbs just have a metal tube to connect fuel line.

[cbr46]

On the fuel line from the tank I used something similar to this -


But probably should have stuck with something like this -


- bob

[wildmanbaker]

cbr46 wrote:
Re: Onan Marquis 5500 on a 2002 Ford F53 chassis

A month ago there was fuel leaking at the fuel pump - the rubber fuel line had gotten old (14 years old) and was cracking around the hose clamp, which was one of those worm screw types around the line.

I highly recommend NOT using this type!
No problem. New fuel line, new clamp, good as new.

Then on the next trip the generator started cutting off after an hour or so, usually with driving and running the roof air in the July heat. A buddy said the fuel pump was collapsing the fuel line between generator and fuel tank based on his experience but after researching threads here on RV.net I decided to replace the fuel pump.

Last Friday I saw the back half of a nice looking Class A in full flames on I-75 near Macon GA. The part that was engulfed was toward the rear, about where the generator would be. That kind of thing can make you nervous . . . . .

So Tuesday I replaced the generator fuel pump (Onan Marquis 5500) with an Airtex unit through Amazon this week. Airtex is the OEM supplier for Cummins / Onan.
https://www.amazon.com/gp/product/B0076D5OI2

During the repair I noticed a very slight drip from the carburetor float bowl drain port. Very slight, but I was able to tight the drain screw 1/16 - 1/8 of a turn. No more drip. The drain screw had loosened by itself and was dropping fuel onto the engine plate but with all the cooling air blowing around I'm sure vapors were airborne as well. Very bad. I also put a drain hose on the port. Good idea.

Then on testing I noticed the fuel filter at the carb (original design has 2) was leaking around the body of the filter.

I always use a wrench on the "big nut" and never torque the filter on the body, (because I've done this before causing one to leak) yet it was loose enough to seep past the seam between body and nut. HAS ANYONE ELSE EXPERIENCED THIS?

At some point Onan recommended removing this filter, relying only on the filter between pump and tank, but I didn't have the hardware to swap it out. Maybe the fuel pump 4 psi causes them to leak?

I've fixed 3 generator fuel leaks in a month's time and witnessed a horrific fire that might have originated from a generator. AM I GETTING PARANOID?

Just check your generators . . . . PLEASE!

Best,
- bob

OK..... Its a know problem using worm drive clamps on small diameter hoses, but just what type of clamp did you use, or recommend?

[MrLugs]

Thanks for the heads up. I replaced the filter at the carb. in our new to us, 2000 f53 with a Marquis 5500 and had an immediate leak at the threads. I nervously tightened it and it seemed ok while running but in the heat when shut down it remained pressurized and leaked a little. What a stink! I noticed pictures online of the filter and it had a red-ish tread sealing compound preapplied, mine did not. So I used yellow teflon tape, which is gasoline proof and it solved the problem.
After reading your post I am now planning to replace the pump, lines and clamps.
Like they say "an ounce of prevention.....prevents a fiery wreck " or something like that.