My Onan Generator is Vexing me!

[Jlemaster]

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!!

[bobsallyh]

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

[Jlemaster]

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.

[ADAD437]

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.

[Jlemaster]

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.

[DFord]

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.