Generator cuts off went hot

[Tomkat12]

I have a onan 5500 and when it gets hot and the gas is vaper locking and I changed the fuel pump and both filters thinking that was the problem and didn’t fix problem Then I pulled it out of compartment and took the covers off and checked for restricted air flow and found nothing Next I took a piece of hose and hooked to fuel pump and the other end in gas can and same problem so that should eliminate fuel line from tank problem then I hooked the fuel pump to a Constance 12 volts thinking that the control board was getting hot and shutting the pump off but it still gets hot and everything I pull the gas line off at the carberator and there is no gas there and try to run pump and pumps running but no gas is flowing. I have tried to find a answer for this problem and not one has said that they did this and it fixed the problem except one person said that they traded there MH Can any one help me please

[twinboat]

Try your test with the gas cap off. Could be creating a vacuum in the tank.

[Tomkat12]

I am going to try today but I did run from a gas can instead of tank

[George Schweikle]

Maybe not specific to your problem, but, does it shut down when driving, or sitting still?. My new Onan 4000 would shut down when driving, but run forever standing. A Cummins Onan tech. suggested installing an auxiliary fuel pump and this solved the driving shut down.

Originally Posted by Tomkat12

I have a onan 5500 and when it gets hot and the gas is vaper locking and I changed the fuel pump and both filters thinking that was the problem and didn’t fix problem Then I pulled it out of compartment and took the covers off and checked for restricted air flow and found nothing Next I took a piece of hose and hooked to fuel pump and the other end in gas can and same problem so that should eliminate fuel line from tank problem then I hooked the fuel pump to a Constance 12 volts thinking that the control board was getting hot and shutting the pump off but it still gets hot and everything I pull the gas line off at the carberator and there is no gas there and try to run pump and pumps running but no gas is flowing. I have tried to find a answer for this problem and not one has said that they did this and it fixed the problem except one person said that they traded there MH Can any one help me please

[MSHappyCampers]

Hi ! Welcome to IRV2! We're sure glad you joined the gang!

No knowledge of Onan gas gennys but noticed you are kinda new on IRV2 and wanted to say hello! Have fun and keep her between the ditches!

Good luck, happy trails, and God bless!

[Tomkat12]

Ok I hook a line to a gas can and ran it and it cut off after 30 minutes so I decided to remove the fuel pump and madeawire long enough to run the fuel pump outside the compartment and still ran it from the gas can and it ran for 1 hour so then I hooked it back to the gas line from the MH gas tank and it ran with 2 ac on for another 4 hrs without any problems. I am going to mount the pump out of the compartment in between the chassis because I think that the pump was getting to hot and quit pumping. If that doesn’t work I will post but I don’t see any problem

[Teamfoxy]

We had a similar problem with out Onan 4000. It would quit after 30-40 minutes and would not run again until it cooled down. From all the information I could gather, older fuel pumps will cut out when they get hot due to the rubber parts inside binding up. Let them cool down and the pump runs again. Like you, I could pull the fuel hose off the carburetor just after it shut down and sure enough, no fuel even though it sounded like it was pumping. Let it cool down and it would pump again. I wouldn't know why your replacement pump didn't work. Perhaps it was sitting on a shelf for a long time? From talking to others, it seems to be an age related problem rather than the amount of use.

My solution was to replace the pump with an after market product. No more problems.

[DDDonkey]

I had a similar issue with our 5500 and my fix was to get some heat shield for the fuel line from the pump to the carb. I used the same stuff they use on spark plug wires, I just cut to length and have been fine ever since. Mine only shut down when driving and it is really hot out 100+ degrees out do to vapor lock. No issues now since the shielding is on.

[Tomkat12]

Ok ran it under load for about a hr in about 85 degrees and it cut off again but this time it wouldn’t restart tried to prime pump and it wouldn’t run new pump so checked voltage to pump and was getting any so after it cooled down it finally got voltage so checked and found that tha voltage for the pump comes from the control board so I ordered a after market board and installed ran test today for 2 hrs and it ran with no problem it had 30 amp load on it when I shut it off hope this is fixed got to be a relay on control board that is acting up when it gets hot but that is the first time that I was able to catch it.

[Mojim]

Originally Posted by Tomkat12

Ok ran it under load for about a hr in about 85 degrees and it cut off again but this time it wouldn’t restart tried to prime pump and it wouldn’t run new pump so checked voltage to pump and was getting any so after it cooled down it finally got voltage so checked and found that tha voltage for the pump comes from the control board so I ordered a after market board and installed ran test today for 2 hrs and it ran with no problem it had 30 amp load on it when I shut it off hope this is fixed got to be a relay on control board that is acting up when it gets hot but that is the first time that I was able to catch it.

[THenne1713]

Guess you are aware GEN will SUCK AIR when MAIN TANK AT 1/4-tank level?; 2) Are you dealing with the $30 pump (chinese, probably?), even new, might still be bad? I have read of some buying new main tank FORD OEM $400 pumps and found them to go bad quickly. FACT: Defects happen. 3) Have also read that GEN Pumps or Main in-tank pumps that suck air can OVERHEAT AND GO BAD, because the fuel is also their COOLING AGENT. Famous saying from my FIL was "Take care of top half, bottom half will take care of itself"; 4) INTERMITTENT PUMP OPERATION can (seem to) work, but then FAIL when you think it is working :-( :-( :-(

[gatorb8]

Sounds to me like the replacement fuel pump may be bad also....

[Tomkat12]

Well I went on trip and ran gen in 95 plus degree days and it ran with no problems so second new pump and new control board is what I did to fix problem went with after market control board Onan wanted 1300.00 dollars for new board I got after market for350.00

[kenautoone]

Longest run on sentence ever ��