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Re: [GMCnet] Onan - Vapor Lock? [message #178484 is a reply to message #178455] Mon, 30 July 2012 22:54 Go to previous messageGo to previous message
Carl S. is currently offline  Carl S.   United States
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma:
Senior Member
Dennis sch wrote on Mon, 30 July 2012 18:51

I had the same problem with mine. I did the same thing you did. then while I was on a road trip it let me down so I stop at a auto zone and picked up a universal fuel pump 3-7psi $50 i installed it in the parking lot 5 years ago and it solved my problems the gen runs like new every time we go. we just got back from a 10 day road trip and it ran every day at least 8hr a day the best 50 bucks I've spent

Robert Mueller wrote on Mon, 30 July 2012 20:04

G’day,

It seems that whenever the OAT gets to the mid nineties the Onan plays up. When the gas is "cold" it runs just fine. As the day
heats up or if we drive with it on it starts to hunt and then finally shuts down. If I try to restart it immediately no joy but if I
let it sit for about 5 minutes I will start and run for a few minutes then it dies again.

When I was here in February I disassembled the carb and cleaned it thoroughly which must be true as when it's cool it runs PERFECTLY
with a voltage output of 120.

Last week before we left I removed the fuel pump and disassembled it. The "piston" moved up and down in the "bore" nicely, both
plastic check valve balls were in fine shape and moved easily.

I removed the solenoid at the inlet to the pump as I reckoned it was one thing less to fail.

I installed a Pertronics mod a couple of years ago and a new Onan coil.

I really think this is a vapor lock problem - it was 97° in Carlsberg, NM today,

Oh yeah, I did check the fuel level in both tanks and both above 1/2.

As they say in this neck of the woods - any idears?

Regards,
Rob M.
USAussie - Downunder

PS - SURE GLAD I INSTALLED A SECOND ROOF AIR LAST YEAR!

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Rob,

I have had the same sort of behavior out of my Onan on the last couple of trips. It would shut off, at first, after about an hour and a half, the about an hour, next time it went for about 30 minutes, next time, 15 minutes. I have done the same as you have, rebuilt/cleaned the carb, replaced all the fuel lines, "overhauled" the fuel pump, plus, I put in heavier oil, and a new LOP switch.

I have concluded, like Dennis (above), that the problem is the fuel pump. I have a new one, a Mr Gasket, from Jim K. in my garage, waiting to be installed. Unfortunately, I won't get a chance to use the coach until October sometime to test it. But, I am confident that the new pump will fix the problem.

Carl Stouffer '75 ex Palm Beach Tucson, AZ. Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member

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