Greetings all,I’m looking for some help here. I have a 2010 37’ Cyclone toy hauler. I bought it used last year and it’s been great. However I’ve never really ran the built in Onan Gold Marquis 5500. The thing was clean and I was always at a full hookup site. I did run it for about 20 minutes each month under load to make sure that the carb stayed clean. So fast forward to now. I am prepping to go elk hunting and wanted to make sure the generator is squared away. I tried to start it and it wouldn’t run. I figured it was the carb and just figured that it had varnish in it. I pulled it off and cleaned the c#*p out of it. The thing looks like new and I blew everything out to make sure the jets weren’t plugged.... still no luck. So I bought a new carb and installed it.... same story. It acted fuel starved and I figured ... well it must be the fuel filters are plugged so I replaced them. This was just a fruitful as the carb replacement. It would run for about 60 seconds, idle down and s*#t out. So I figured .... must be a fuel flow issue, so I replaced the fuel pump... still no joy! I just replaced the spark plug today ( which the old one looked horrible) and it’s still doing the same thing! It does restart after every time it dies, but it just does the same thing. I wanna fix this thing so any help would be greatly appreciated. I’ve tried adjusting the carb altitude adjustment knob and it doesn’t help. I took a video of it that I’m gonna try to attach to this post if possible. If it’s not and you’d like to see it please message me and I’ll send you the video if you think it’ll help!! . Hopefully I can get some help here, because I’m sure this is just something small and stupid, but I’m out of ideas! Thanks in advance everyone!!

Where's the generator getting the gas from? If it's through a rubber hose, that hose may be cracked a sucking air instead of gas. I saw someone post a troubleshooting tip on here about draining the fuel bowl as soon as the generator stopped to see if there was anything in it. Leave the drain open and press the stop button to prime the generator and see if you get a good stream of gas coming out. If not, buy enough gas line to run from the fuel pump to a gas can and see if it continues to run. That would prove the trouble is between the fuel pump and gas tank.Start troubleshooting and stop throwing parts at it.

That’s a really good idea. I’ll try that tomorrow. It’s just really bizarre that it’ll fire back up immediately without priming it, after it dies. It only runs for that 60ish second time frame but I all I have to do is hit the start button. It initially runs pretty solid but then isles down and stops again.

Jlemaster wrote:That’s a really good idea. I’ll try that tomorrow. It’s just really bizarre that it’ll fire back up immediately without priming it, after it dies. It only runs for that 60ish second time frame but I all I have to do is hit the start button. It initially runs pretty solid but then isles down and stops again.i will be following this post, i have an onan 4000 doing the same thing, maybe i can learn something from this.

So on further troubleshooting.... I have determined two things... First and foremost it’s not fuel starvation, it’s actually flooding itself and dying. This is the case regardless as to what I clean or do to the carb. Everything is intact with the float and the needle/seat is perfectly clean. It’s obviously been running rich for a long time because the old spark plug was nasty and covered with carbon, and the brand new one that I put in ended up the exact same way. It happened to the new one after the thing only running for like 30 seconds a crack and then dying out. Second and most importantly, I realized today that I had forgotten that when I pitched the trailer, I got an extended warranty with it that covers nearly everything.... including the generator! Thus I’m going to take it into the professionals to get it fixed as it will only cost me $100 bucks for the copay. It’s obviously something to do with either the float or the pressure sensor that attaches to the bowl, not telling the pump to stop sending fuel to the carb, but it’s over my head as to what could be causing it as I’ve checked everything I can think of.

Jlemaster, please come back and let us know what they find.

My Onan Generator is Vexing me! | Good Sam Community

Jlemaster
Explorer
Dec 12, 2019
Yup! It was freaking expensive. But worse than that... it took like 4 months to get that done. It was done at a Cummins dealership because no one else would fix it.
4x4van
Explorer III
Dec 12, 2019
$689 WITH a warranty? :O
ADAD437
Explorer
Dec 07, 2019
wa8yxm wrote:
True story about a Honda EU-2000i.. Same symptoms you have Ran for like 2 minutes. then sputter die.. Checkd gas (tank full) did it again, and again, and again and finally I ask the park employee working on it if he'd opened the vent in the fuel cap. Ran for 2 or 3 hours after than and stopped when someone turned it off (A park employee).

Possible fuel tank vent issue. OR Clogged screen on fuel pick up

Though my money is on a bad fuel line as per a prior replay.

so far i have replaced fuel filter, fuel pump, carburater, fuel line from pump to carb., put short hose in fresh can of hi test gas still dies after 3 or 4 min. i might add i am getting code 36.
wa8yxm
Explorer III
Dec 07, 2019
True story about a Honda EU-2000i.. Same symptoms you have Ran for like 2 minutes. then sputter die.. Checkd gas (tank full) did it again, and again, and again and finally I ask the park employee working on it if he'd opened the vent in the fuel cap. Ran for 2 or 3 hours after than and stopped when someone turned it off (A park employee).

Possible fuel tank vent issue. OR Clogged screen on fuel pick up

Though my money is on a bad fuel line as per a prior replay.
Jlemaster
Explorer
Dec 07, 2019
Sooooo...... It’s funny that you posted this today... I just got it back from Cummins YESTERDAY!! They ended up replacing the fuel pump (they said it wasn’t the correct part for that generator), the spark plugs, both ignition coils, carburetor and the rocker cover seal. It works fine now. I started it and ran it for over two hours just to be sure. Cost me 689.00 and the warranty company paid 1100.00. So almost 1800 total to fix it.
ADAD437
Explorer
Dec 07, 2019
still waiting, what did they find out?
ADAD437
Explorer
Nov 28, 2019
Jlemaster wrote:
It was replaced, but it was with a factory Onan pump. I’ll definitely post a follow up once they repair it.

so what did they find? i am having exactly the same problem.
Jlemaster
Explorer
Sep 10, 2019
Yeah hopefully they unscrew the mess on the 19th . That’s when it goes in for service. I think it’ll probably be a pretty quick fix for people that work on them all the time.
mchero
Explorer
Sep 10, 2019
Dford has some excellent suggestions!

I have seen some NASTY generator fuel line(s) from the gas tank. Road dirt and debris get kicked on top of fuel tank. Dirt gets wet and slowly dries creating some nasty rust. Also brittle fuel lines.
Might not be the issue but worth looking into.

How old is the gas that the generator is drawing from?
bounder39zman
Explorer II
Sep 10, 2019
you have a 2 cylinder engine....replace the other spark plug if the one you pulled looked bad.I find NGK3432 work best (BPR4EY). Onan says gap should be .025

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