Generator Surging/Dying After Hours of Operation

[john_engel]

I bought the RV with 77 hrs on generator. It didn't run. I cleaned slip rings and it ran but surged and died after 20 mins sometimes, sometimes after hours of operation. I've changed fuel, air, oil filters, changed oil, fuel pump, spark plugs. I've done the Seafoam with external gas can for six hours of run time...under load but had voltage too high due to governor screw adjusted too high. Adjusted it back down and surged and died after an hour. I went back to the tank fuel line and adjusted governor down. Did voltage checks, not hertz (don't have that on my voltmeter). Runs at 129V with no load, drops to 107 volts with Microwave, A/C, hairdryer.

Bottom line, it goes for a while, sometimes hours but eventually surges and dies. Took it to a football game, sub zero temps...ran for four hours...died. Fired it back up in the middle of the night...it ran for 32 hours until time to leave...the next weekend, it runs for 8 hrs, then surges and dies...we wait a while...it fires up and runs for a bit but always ends up surging and dying at some point...this is driving me nuts.

Probably Pointless observations: Problem gets seemingly worse in higher temperatures. There may be a connection to the door/automatic step as I've had it running and this caused it to surge and die on 3 occasions. It won't stay running while RV is going down the road. Longest I've had it running in transit is 1 hour.

Not Pointless: Altitude screw has to be out at least 4 complete rotations to run. The generator seems to be running rich...smelly but no smoke, trips the CO2 detector sometimes. I've pulled the carb and cleaned it, tried to go 1 1/4 turns out with the Alt adjustment but it wont' start that way. There is no idle adjust screw...the only ones I have are the governor adjust screw and the Alt adjust screw. They are most certainly out of adjustment as I have been endlessly tinkering with both.

Sorry about the long post but I'm at my wits end. No good ONAN shops here in Toronto, this seems like a quick fix but I'm just missing the boat on something.

Please help!

[HTElectrical]

Be careful running too much rubber fuel line. It could collapse under suction.

Different animal, but my friends 74 camaro was basically doing the same thing. Couldn't find the problem. It turned out to be a 4" piece of rubber fuel line from tank to steel fuel line that was collapsing.

[john_engel]

That is next step...its rubber hose from pump to frame...then steel line bck to the tank...then rubber into tank...the steel line is ancient and rotted...gonna replace wuth new rubber hose all the way back and new gas cap...thanks guys...will update once I try it...

[rockhillmanor]

I fought the same problem. Several mobile repairs. They replaced filters etc etc etc. Tested it and it would run. Then I'd get back on the road and like yours would just die.

Then I stopped in Kentucky I called mobile repair and begged them to come out to find the problem and not leave until they did! :B

Fuel Pump. It will test ok but when you pull it out you can see the rubber gets tiny holes and cracks in it and the rubber is fatigued so it runs fine sometimes and then quits.

He replaced the fuel pump AND....then he showed my how much EXTRA fuel line there was under my coach!!

Which would make the fuel pump work harder to try and suck it thru all that extra line which was tucked up and wound all over the undercarriage of my MH! Go figure!

He shortened that line 'substantially' and reran it in a more direct line from tank to gen and haven't had a problem since.

[jplante4]

+1 on the fuel lines. Surging could be from and intermittent crack opening in the fuel supply line.

[eHoefler]

Replace all rubber fuel lines. They are most likely not compatable with today's fuels.

[john_engel]

Already changed pump

[manitoba_travel]

Have same age gen onan 5000 , it was surging and stopping tested fuel pump
It would run then stop when it heated up, they are low pressure ,
A new pump made it run like a champ,

[The_Texan]

After the simple check to make sure the gas cap is not plugged, I would then turn my attention to the old fuel line. After that, I would be looking at the generator innards of the fuel tank.

[john_engel]

Not sure about fuel level...well above half way on last series of tests...the gas cap theory is interesting...the last time I was tinkering...i cracked the fuel line loose at the filter to check the filter and there was an air release....not sure if it was suction or pressure...filter was clear

[MrWizard]

sea foam is good stuff
BUT it wont fix a bad float in the carb
or a weak fuel pump
or a bad /clogged pickup tube in the RV fuel tank
what was the fuel level during the 'problem times'
and have you tried running the generator with the gas cap loose
a bad vented cap that is clogged can cause problems with the generator that you might see with the drive engine becuase of the difference in fuel systems

[john_engel]

Sorry...1998 RV...Onan 4000 Emerald Plus

[gbopp]

How old is the RV/generator? I'm just taking a wild guess but, could the fuel lines to the generator be getting soft and collapsing?
If the problem is worse in warmer weather, it may be a possibility.