Onan 5500 Generator in Holiday Rambler 1998 Endeavor

[dalefuji]

Generator runs sometimes and then shuts off.
Replaced with new:
Spark plugs, oil change, oil filter, air filter. "still no run"
Replaced:
New carburetor, New fuel pump, New fuel filter, No gas line hose from carburetor to fuel pump.
"still no luck"
The in line 10 amp fuse above stop/start switch is okay. The 20 amp
two blade fuse by breakers is okay.
I help "stop button" in for 15 seconds to prime Gen. and then hit start button and it started and ran for 60-90 seconds and then started getting rough and shut off and would not start.
I ordered new 5 blade relay plug under air intake to see if that is problem.
Are there any other in line fuses that could be problem
Any suggestions would be greatly appreciated.

[dalefuji]

Thanks for input. gas lines were changed Last fall. 2022

[Ed_Manifold]

My Onan 7500 was doing the same thing a couple years ago. It is a 2002 and I had serviced it before our trip. When I got back I took it to my RV mechanic and he found bad/ rotted fuel lines, changed them and it now runs fine. With the age of your coach this could be the problem. When I had serviced the generator I didn't check the lines and I wouldn't have been able too see them up in the service area. Good luck.

[udidwht]

You need to find someone with a G-Man set and have them diagnose it within minutes.

[lfeather]

Could be fuel lines are weather cracked and sucking air. Try new fuel line in separate fuel tank from fuel pump.

Larry 2014 Reyo P

[enblethen]

Believe that is an isolation relay between remote start and gen start.
Thanks for the update!

[Snowwing]

I would really like to know what this relay's function is.
Thank's
RC

[Rick_Jay]

dalefuji,

Glad to hear you have it running! Kind of makes me wonder what the original problem, was though!?!?! 🙂

Thanks for posting your success...however you achieved it. 🙂

~Rick

[dalefuji]

Problem solved, Generator 5500 is running smoothly and runs my air conditioners.
I put the original fuel pump and carburetor after cleaning back on. Today I got a Bosch 5-blade relay that is located in air cleaner box. I started Generator and it runs excellent. Problem solved.
I want to thank everyone for all your input and suggestions. It was greatly appreciated. Thank you all.

[Rick_Jay]

dalefuji wrote:
Yesterday I spoke to friend at RV Dealership and he told me to hold stop button in for 15 seconds to prime carb. I did that and generator started and ran for about 3-4 minutes. After that it would not start. Today we disconnected gas line from main tank to fuel pump and hooked hose up to fuel pump and dropped hose in gas can. Generator would not start.

When you primed the generator, it started. I'm assuming it was running pretty well and not sputtering or running rough or you would've mentioned that. That to me would suggest that the carb is probably OK.

After you primed it, it ran, and then stalled once the fuel was used up in the float bowl. That's normal if there's not sufficient fuel being fed to the carb. Did you repeat the priming procedure every time you tried to restart it after that? If you just dropped the fuel line into a can of gas, it'll take A LOT of cranking before it can pull up enough fuel into the float bowl to fire.

Well, good luck in your troubleshooting. I'm still leaning toward it being a fuel line or possibly a fuel pump problem. I'll be very interested to hear what your solution turns out to be.

~Rick

[dougrainer]

dalefuji wrote:
The spark plug gap is set at .025 and plugs come set at .035 could an issue.
I always kept oil level at full mark, some say that oil level should be at
low level mark because dip stick is wrong?????
Is there a sensor on oil level that could be causing Onan not to start??

The Onan WILL start with the switch engaged. IF you have a LOPKO(low oil pressure switch) that is defective the Onan will then die once the start button is released. There is NOT any such problem with needing to have Oil Level lower than full on the mark. Where did you get your Carb? ONAN carb or aftermarket? Fuel Pump. ONAN or aftermarket or local auto part store. Doug

[enblethen]

Some Onans have one of these.1 PSI switch

[dalefuji]

The spark plug gap is set at .025 and plugs come set at .035 could an issue.
I always kept oil level at full mark, some say that oil level should be at
low level mark because dip stick is wrong?????
Is there a sensor on oil level that could be causing Onan not to start??

[dalefuji]

Yesterday I spoke to friend at RV Dealership and he told me to hold stop button in for 15 seconds to prime carb. I did that and generator started and ran for about 3-4 minutes. After that it would not start. Today we disconnected gas line from main tank to fuel pump and hooked hose up to fuel pump and dropped hose in gas can. Generator would not start. We come to conclusion that new carb. is not working and are going to clean old one and put it back on and see if Generator starts.

[Rick_Jay]

dalefuji wrote:
I took fuel line from fuel pump and stuck it in gas can and no luck...

This could just be semantics, but to be clear, you need to disconnect the fuel line going TO the fuel pump, not from. That is, the fuel line coming from the gas tank. That's probably what you did, but just want to make it clear. To do this, you'll probably need an additional length of fuel line to drop down from the pump to the gas can.

I still think your symptoms still sound like fuel starvation.

Can you repeat your test where you primed the engine and then tried to start it? If that works, it's most likely a fuel problem.

When you go to start it, does it "pop" or show any signs of trying to start? Have you tried spraying any "quick start" spray into the carb to see if that would get it to "pop"?

~Rick