Question Does Not Like to Run While Moving

[WB2020ClassA]

I have an Onan 5.5kW Marquis Gold (HGJAB series) in my 202 WB Class A. The generator runs just fine when parked. But, when I try to run it while traveling, for example to run a rooftop air conditioner in hot weather), it will only run for a few minutes then it quits. On my in-coach display it shows error code 36. That's not very useful - the Onan owner's manual says to check the fuel level (it feeds from the coach 80 gallon tank), the spark plug (would not run stationary if spark plug was bad), the air filter (it has less than 25 hours on it) or "mechanical damage" (if there were mechanical damage it would not run stationary with mechanical damage). I tried to contact the Cummans/Onan "help desk" but all they would do is refer me to a dealer. Anybody else experience this issue or have any ideas?

 

[Richpatty]

I have not had that specific problem, but when I did have a stalling issue with my gas Onan a few years ago, after a few minutes of running, it was the fuel pump…

 

[SGilbert]

Pure wild a$$ guess: Your genny exhaust pipe is either straight perpendicular to or somewhat forward facing. That would force air INTO the exhaust, making exhaust from genny blocked.
It needs to be facing somewhat, or totally, rearward.

 

[Wemustrv]

What is yout fuel level? Most have shutoff somewhere around 1/4 tank. Going down the road fuel could shift and causes shutdown while moving. You may also want to check the fuel filters

 

[Neal]

In my experience Onan generators are very sensitive to oil level. If over filled, this can happen. I had this happen once and had to drain a cup (about 8 ounces) of oil out after researching this and then the problem stopped.

 

[WB2020ClassA]

Pure wild a$$ guess: Your genny exhaust pipe is either straight perpendicular to or somewhat forward facing. That would force air INTO the exhaust, making exhaust from genny blocked.
It needs to be facing somewhat, or totally, rearward.

Thanks, good guess, but the exhaust pipe is not damaged - it projects straight out under the rear bumper just like it came from the factory.

 

[WB2020ClassA]

What is yout fuel level? Most have shutoff somewhere around 1/4 tank. Going down the road fuel could shift and causes shutdown while moving. You may also want to check the fuel filters

Thanks. I know that fuel feed is higher than bottom of tank so genset can't starve chassis engine. The last try, I was driving with a nearly full tank. The genset does not have more than 250 hours so filters should be ok, especially because it runs fine stationary. I'll check them, though.

 

[WB2020ClassA]

In my experience Onan generators are very sensitive to oil level. If over filled, this can happen. I had this happen once and had to drain a cup (about 8 ounces) of oil out after researching this and then the problem stopped.

Thanks - I am very careful to check the oil level before and during every trip. Years ago, I knew somebody who forgot to check and his generator in Allegro Bay ran dry in the middle of the night.

 

[Scooterfan]

Had the (exact) same problem last year on our (same) generator. Changed out the fuel pump and it solved the issue. They are relatively inexpensive and easy to swap out. EXCEPT...it's a good opportunity to install a fuel shut off valve because when you disconnect the fuel line, gas will flow like a river Don't ask me how I know this. Good luck. Blessings

 

[newmarokie]

It nearly has to be either the fuel filter or the fuel pump. Two hundred and fifty hours on the filter is not alot, but one tank of bad fuel can stop up a filter. I lean more towards a weak fuel pump. Sitting in the campground, the genny is not competing against the engine for fuel and runs fine. On the road the genny and engine are sharing available fuel. Where is the fuel tank in relation the genny and the engine?

 

[WB2020ClassA]

Had the (exact) same problem last year on our (same) generator. Changed out the fuel pump and it solved the issue. They are relatively inexpensive and easy to swap out. EXCEPT...it's a good opportunity to install a fuel shut off valve because when you disconnect the fuel line, gas will flow like a river Don't ask me how I know this. Good luck. Blessings

Thanks. I heard this idea somewhere once but it was just thrown out as an idea. Glad to hear from someone with the same generator and problem. Seems like I shouldn't have to change a fuel pump at 257 hours, but ...
I think I can figure out how you know... I have a plan for that; it involves a golf tee and hose clam.

 

[newmarokie]

Scooter & WB,
I have a QD8000. It has a secondary fuel filter on the bottom behind a inspection plate that I don't think had been changed since it was sold new (I bought it used). Does the gas gennies have those?

 

[WB2020ClassA]

Scooter & WB,
I have a QD8000. It has a secondary fuel filter on the bottom behind a inspection plate that I don't think had been changed since it was sold new (I bought it used). Does the gas gennies have those?

Nope. Thanks

 

[WB2020ClassA]

Thanks. I heard this idea somewhere once but it was just thrown out as an idea. Glad to hear from someone with the same generator and problem. Seems like I shouldn't have to change a fuel pump at 257 hours, but ...
I think I can figure out how you know... I have a plan for that; it involves a golf tee and hose clam.

By the way, I'm also going to change the fuel filter connected to the fuel pump on the bottom of the generator. The Onan manual lists 3 fuel filters: gasoline, LPG and one labeled EFI (#0147-0860). I have no idea what that references, but the only fuel filter I can see between the fuel line from the coach gas tank to the carburetor is the one attached inline before the fuel pump (0149-2341-01).

 

[Scooterfan]

If I recall correctly, there's also a fuel filter on the carburetor intake...

 

[WB2020ClassA]

If I recall correctly, there's also a fuel filter on the carburetor intake...

Thanks - I took a look and I could not see one - the fuel line from the fuel pump goes into a fitting that connects directly to the carburetor bowl; unless what looks like a fitting is another fuel filter.

 

[WB2020ClassA]

Thanks - I took a look and I could not see one - the fuel line from the fuel pump goes into a fitting that connects directly to the carburetor bowl; unless what looks like a fitting is another fuel filter.

Just to be sure - I took a look at the part number from the owner's manual on the Cummins-Onan site - it is for EFI engines with different "spec" codes than the gas QG5500 HGJAB (J-L) and I do not see anything that looks like it near the carburetor.