Generator Not Staying On When It's Over 90 °F

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Generator Not Staying On When It's Over 90 °F

July 10, 2024, 07:03:57 pm

My generator (Onan Emerald Plus 4000) runs very well when it's not very hot. I just ran it for an hour a couple of days ago when it was about 75 °F, with the A/C on and set to maximum cooling (the compressor turned on and off several times while the generator was running).

However, when the temperature is 90 or 95 °F or higher, the generator first starts as usual, but then it shuts down after three or five minutes (even without any load) and will not start again until the temperature is much lower again.

As far as I can tell the generator has enough oil, and the oil on the stick looks clean and yellow. I changed the spark plug, and it didn't make a noticeable difference. I checked the air filter, and it looked nice and clean. That's pretty much all I can do myself.

I asked a repair shop owner who also works with RV generators and other engines if he had heard about this symptom - and he had not. He also had no specific idea what this might be pointing to.

Does this sound familiar to someone and possibly points to a certain problem?

Klaus

Re: Generator Not Staying On When It's Over 90 °F

Reply #1 – July 10, 2024, 08:14:08 pm

Two guesses.
First, it could be a fuel line leak that happens when the rubber fuel line gets hot and soft, allowing a crack to open up enough to suck in air instead of fuel. When the fuel line cools, the crack closes up.
I saw this in early 2000 LDs and it was (is) a common problem. There are two sections of rubber fuel line, one down at the generator's fuel inlet and another up on top of the fuel tank. The top rubber hose requires the fuel tank to be partially lowered or dropped. The process has been discussed here many times, search the archives for more information.

Second, a less common issue is an electrical problem that only shows up when the part in question gets hot. Seen in coils and electric ignition modules.

It's most likely the first guess.
Larry

Re: Generator Not Staying On When It's Over 90 °F

Reply #2 – July 10, 2024, 08:24:39 pm

Thank you, Larry. I will look for these discussions and go from there. Klaus

Re: Generator Not Staying On When It's Over 90 °F

Reply #3 – July 11, 2024, 01:51:08 pm

A friend was having a similar issue... found a YouTube video about too much oil causing shutdown. Her oil had recently been changed and was right at the full mark, not over. It had run fine in cooler temps. After checking and ruling out fuel issues, decided to remove some oil with an old syringe... Got level down to about halfway between full and low marks. Doesn't make any sense to me but lowering the oil level slightly seems to have fixed it.

Re: Generator Not Staying On When It's Over 90 °F

Reply #4 – July 11, 2024, 03:07:10 pm

Our LD was doing the same when we bought it a couple of years ago. Thought it was the line from the gas tank but after changing it and the pump in the tank that was not the problem. Turns out it was the generator fuel pump. Ours would overheat after about 10 minutes and quit. I replaced it and have never had another issue. I was able to find a “green label) Onan pump on line but even the knock-offs may work as well.

Re: Generator Not Staying On When It's Over 90 °F

Reply #5 – July 11, 2024, 03:36:45 pm

Hi Frank; Thanks, or as Larry said "the affected part over heats and quits", could easily be the fuel pump itself. Or some other part too, associated with the electrical. Klaus,, with a 2001 likely has the same Onan Emerald Plus (noisy beast, but pretty reliable) that I have. Amazon lists fuel pumps in the $20-$40 range. Maybe made by the same Chinese company that makes them for Onan. RonB

Re: Generator Not Staying On When It's Over 90 °F

Reply #6 – July 11, 2024, 07:26:31 pm

Quote from: Duoglide - July 11, 2024, 03:07:10 pm

Our LD was doing the same when we bought it a couple of years ago. Thought it was the line from the gas tank but after changing it and the pump in the tank that was not the problem. Turns out it was the generator fuel pump. Ours would overheat after about 10 minutes and quit. I replaced it and have never had another issue. I was able to find a “green label) Onan pump on line but even the knock-offs may work as well.

I had the same problem with my Onan, and confirmed it was the pump and not a bad fuel line by putting a short fuel line on the pump and the other end in a gas can underneath the coach. Same symptom - stopping at high temperatures. Replacing the pump fixed the problem.

Re: Generator Not Staying On When It's Over 90 °F

Reply #7 – July 12, 2024, 12:12:12 pm

Thanks for all replies!

I already bought air, oil, fuel filters, and a fuel pump. Since I assume it is easier to replace the fuel pump than the fuel lines, I will start with that.

Klaus

Re: Generator Not Staying On When It's Over 90 °F

Reply #8 – July 12, 2024, 12:33:32 pm

Quote from: Eric Greenwell - July 11, 2024, 07:26:31 pm

I confirmed it was the pump and not a bad fuel line by putting a short fuel line on the pump and the other end in a gas can underneath the coach.

Testing this way is relatively easy and will determine if a leaking fuel line or a bad pump causes the generator to stop when hot.

Since the OP's rig is a 2001, it was built during the years when the fuel lines rotted prematurely. The rubber fuel line was old when it was installed.
Our 2003 LD's lower line was replaced within two years when it developed cracks, and the upper line lasted several more years before it started leaking.

Larry

Re: Generator Not Staying On When It's Over 90 °F

Reply #9 – July 12, 2024, 03:30:17 pm

"...built during the years when the fuel lines rotted prematurely. The rubber fuel line was old when it was installed."

We can thank miserly Ed Newton for that! He was of the mind that you don't throw away material that's already paid for.
Many of us have had to replace both upper and lower gen fuel lines because of that. I replaced the line from the tank to the gennie with solid stainless.

Re: Generator Not Staying On When It's Over 90 °F

Reply #10 – July 12, 2024, 04:57:36 pm

Quote from: Larry W - July 12, 2024, 12:33:32 pm

................ The rubber fuel line was old when it was installed. ....................

That's interesting about the line being old when installed. It was about 2004 was when MTBE started to be banned and ethanol started to become "the additive of choice" in the gasoline industry. There were many cases of premature fuel line failures with ethanol as "ethanol resistant" hose wasn't always used until sometime after about 2004. My Dad had an older car that developed fuel leaks around 2004-2005 when all the fuel had ethanol where he lived... Hose that had been soft for years turned rock hard very quickly once he started using E10. It was difficult for us to find ethanol resistant fuel hose in stores around that time, they still had the "old stuff".

From that experience I would have guessed the generator fuel line failures for vehicle built pre-2004 or so were ethanol related and not age related.

Re: Generator Not Staying On When It's Over 90 °F

Reply #11 – July 12, 2024, 07:02:35 pm

Hi Mark; MTBE ( methyl tertiary butyl ether) started being used to oxygenate fuel to make it burn more completely back in 1979. Problems in about 1999 when my rig was made, with MTBE leaking from tanks into groundwater, caused a switch to ethanol in 2002-2003 (California). Because it absorbed water, it caused rust problems in tanks, and affected older hoses in pre ethanol vehicles. Right now I have a vapor leak somewhere. Rats maybe! also. I keep resetting the MIL (check engine light in a '99 Ford just says "engine maintenance needed", but not a liquid leak, and the generator still runs. I'm suspecting the carbon cannister purge line. Got to get under there to inspect those lines. RonB

Re: Generator Not Staying On When It's Over 90 °F

Reply #12 – July 13, 2024, 09:51:44 am

Hi Ron, I hope you find your issue soon! It can be maddening to fix issues like that. I was just surprised to hear stated that the reason for premature generator hose failures was "old fuel line installed at the factory" when I assumed it was the "switch to ethanol as an additive".

Thanks to the knowledge and information on this forum, one of the first things I did on my 95 was drop the tank and replace the little piece of generator connector hose... it wasn't leaking yet... but it was in pretty bad shape... it did split during removal. (Installed new fuel pump module at the same time)

This forum sure saved me from a big hassle down the road as you know the generator hose probably would have failed at the worst time!

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