Onan genset stops running--------Fixed

[427435]

Finally got the MH out. The genset started up OK and I let it run while I did some other things with the MH. It started to surge after 10-15 minutes and quit. It restarted after setting for a while. That cycle continued several times this afternoon.

My best guess is a mouse nest causing the overheat temp sensor to kick out. I won't have time to deal with it for a couple of weeks, but I'm interested in other possibilities to check before I pull the shrouds (which looks like it requires pulling the genset out). 😞

[wildmanbaker]

427435 wrote:

BobR wrote:
Start by dis-connecting generator fuel line. Mix a gallon of gas with SeaFoam and run generator for 15 minutes from gas can fuel(Have can higher than Genny for gravity feed). Let sit for at least 30 minutes and then restart. It just may be a gunked up carb. Repeat again if necessary. Might have to reset choke. If that doesn't work, then look at other culprits like fuel pump and filter.

Running from a separate fuel source would determine if it's a bad fuel line or a bad pump. If the carburetor were the problem, it wouldn't start and run for 20 minutes.

X2, its easer than reaching the tank connection hose.

[427435]

BobR wrote:
Start by dis-connecting generator fuel line. Mix a gallon of gas with SeaFoam and run generator for 15 minutes from gas can fuel(Have can higher than Genny for gravity feed). Let sit for at least 30 minutes and then restart. It just may be a gunked up carb. Repeat again if necessary. Might have to reset choke. If that doesn't work, then look at other culprits like fuel pump and filter.

Running from a separate fuel source would determine if it's a bad fuel line or a bad pump. If the carburetor were the problem, it wouldn't start and run for 20 minutes.

[BobR]

Start by dis-connecting generator fuel line. Mix a gallon of gas with SeaFoam and run generator for 15 minutes from gas can fuel(Have can higher than Genny for gravity feed). Let sit for at least 30 minutes and then restart. It just may be a gunked up carb. Repeat again if necessary. Might have to reset choke. If that doesn't work, then look at other culprits like fuel pump and filter.

[soxbrat]

Here's what solved my problem, yesterday. Started the genset. it ran for 3 minutes before surging and dying. It wouldn't restart. Amp draw was a consistent .78 amps right up to engine shutdown. I happened to have another, used, pump that I installed. This pump showed .80 amp draw. Generator started, powered up and ran for an hour with A/C running. I'm calling this problem solved. A new pump from Cummins was about $120 so it's not an inexpensive fix, but it was simple to get to and only about a 5 minute swap so you shouldn't have to pay to have it replaced.

[timmac]

I am having the same problems now that's its warm, I have found out when leaving the access door to genny open it stays running meaning it gets more air circulation and not overheating, try that and see if it stays running than you can narrow down the issue without throwing parts at the genny.

[mcal63775]

NOT to the carb....but to the FUEL PUMP... my bad...lol

[mcal63775]

My Onan 7000 Marqui experienced same problem. AFTER a new fuel pump and fuel filter (carb was replaced a year prior to this problem), it STILL continued. I ran a new gas line to fuel pump and from a gas can....it ran great. Found a split gas line from fuel tank to fuel pump. Replaced the line. Problem resolved.

[johntank]

427435 wrote:
Finally got the MH out. The genset started up OK and I let it run while I did some other things with the MH. It started to surge after 10-15 minutes and quit. It restarted after setting for a while. That cycle continued several times this afternoon.

My best guess is a mouse nest causing the overheat temp sensor to kick out. I won't have time to deal with it for a couple of weeks, but I'm interested in other possibilities to check before I pull the shrouds (which looks like it requires pulling the genset out). 😞

I just had a similar problem with my Onan 4000 in my 5er fuel pump and filter new last year so had good fuel flow, a Cummins shop in my area after checking it out said it was a bad carb.

PM me if you want more info.
John

[soxbrat]

I'm having a similar problem in a 5th wheel toy hauler. I've replaced everything,i.e., spark plugs, filters, etc., except the fuel pump. I've been trying to find out what the amp draw should be for the pump so that I can check it out.I'll be interested to see what your final analysis is. If I get this problem corrected I'll post.

[mikestock]

Surely sounds like a possible fuel line or filter problem. I found that Tiffin, for some reason, places a small fuel filter ahead of the Onan, built in, filter. Cummins said to take it out and replace it with a hose splicer. I did so and my problems ended.

I don't, personally, know if Tiffin is the only builder to add this useless filter.

[sdianel_-acct_c]

The generator has codes if you can get a copy of them. Ours did the same thing and we took it to Cummins. The tech tried the switch and said "fuel line getting air".... we had to replace the fuel lines going to the generator.

[gbopp]

Did you change the fuel filter lately?
I solved a surging problem on our Onan 5500 by changing the fuel filter.

[snarley]

Very similar sounding problem to what I had- turned out to be fuel pump because of very high air (+95 deg F) temperatures- changed the pump, less than $ 50 thru Amazon, and been OK for two plus years.Story is some made in China fuel pumps are known to have this issue.

[jwmII]

Check the rubber fuel line from the tank to the gen. fuel pump. Yours is 15 or so years old and probably dried out and cracking. This lets the fuel pump suck air along with some fuel and eventually it cannot keep up with the engine fuel requirements and shuts it down.

While you are in there check the other rubber lines going to and from the tank as they are due for replacement as well.