Onan 5500 Issues

[F463216]

My Onan 5500 Marquis generator does not want to keep running. Initially, when it is cold, it will stat and run without a heavy load (only the charger, i suspect), then will die - not always suddenly; sometimes it lugs down, picks up, and eventually lugs down to stop. When it is running it seems to generate ample power, as the A/Cs work. The fuel pump delivers ample flow, with and without the fuel filter.

I have replaced the plug, oil, oil filter, air filter, fuel filter, fuel pump and fuel line as far as I am able tho reach. This is in a '99 Fleetwood Southwind (class A). I noticed that the oil was slightly overfilled, so I drained it to the point that it is barely in the safe area on the dipstick.

The generator has 1,688 hours on the tach, all but 260 having put on it in the past three years. I suspect that the previous owner(s) seldom ran the generator as should have been to keep it in top shape. The motorhome had slightly more than 61,000 miles on it when purchased.

All service and replacement parts used by me have been Onan parts. Until the last two oil changes all oil used was Onan. It now has Mobile One.

The maintenance that I have performed, as stated above, has resulted in no change with he problem.

Model #5.5 BGMFA26105H, S/N A990848563.

I cannot determine what might be keeping it from running properly. My suspicions: (carburetor, though when it runs, it runs fine; or, 2) bad (cracked or clogged) fuel line or pickup where I cannot get to it.

 

Any advice out there?

[desertdeals69]

When I was an Onan dealer we would use a outboard fuel tank with reg gas and a primer bulb.  If the unit ran fine we would replace the fuel line all the way to the tank.  If it faltered running on the aux tank we would use the primer bulb.  If it ran ok then there would be something wrong in the fuel delivery system.  Most of the time it was a crack in the fuel line.

[ianbullock]

You didn't mention how long it ran before it "lugs down to a stop". Could it be the auto choke?  I know I had a similar situation on a previous Marquise 5500.

[dickandlois]

On 7/25/2019 at 4:39 PM, F463216 said:

My Onan 5500 Marquis generator does not want to keep running. Initially, when it is cold, it will stat and run without a heavy load (only the charger, i suspect), then will die - not always suddenly; sometimes it lugs down, picks up, and eventually lugs down to stop. When it is running it seems to generate ample power, as the A/Cs work. The fuel pump delivers ample flow, with and without the fuel filter.

I have replaced the plug, oil, oil filter, air filter, fuel filter, fuel pump and fuel line as far as I am able tho reach. This is in a '99 Fleetwood Southwind (class A). I noticed that the oil was slightly overfilled, so I drained it to the point that it is barely in the safe area on the dipstick.

The generator has 1,688 hours on the tach, all but 260 having put on it in the past three years. I suspect that the previous owner(s) seldom ran the generator as should have been to keep it in top shape. The motorhome had slightly more than 61,000 miles on it when purchased.

All service and replacement parts used by me have been Onan parts. Until the last two oil changes all oil used was Onan. It now has Mobile One.

The maintenance that I have performed, as stated above, has resulted in no change with he problem.

Model #5.5 BGMFA26105H, S/N A990848563.

I cannot determine what might be keeping it from running properly. My suspicions: (carburetor, though when it runs, it runs fine; or, 2) bad (cracked or clogged) fuel line or pickup where I cannot get to it.

 

Any advice out there?

This is a link to the Onan Handbook that covers the generator and a parts list is on page 21.

     https://cdn.ltvdns.com/leisurevans.com/owners/3rdparty/Cummins-Onan-RV-Generator-Handbook.pdf

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Rich.

[F463216]

Thanks, everyone for your replies. I'll add spray foam to the fuel tank. I now have a half-tank of gas. Too, I'll slowly spray some seafoam into the carb to help clean it out... or maybe Risolone. If problem does not wane and still persists I'll do the remote fuel source set with a bulb pump.