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

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.

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.

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.

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.

soxbrat wrote:
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.

I hope you found the problem, but I don't know if I'd make the same conclusion about the fuel pump being the issue with the currents you measured. The difference between 0.78 Amps and 0.80 Amps is only about 2.5%. That's within the range of accuracy on DC current scales of many DMMs and Multimeters, so depending upon the meter you're using, it might not be an accurate indicator. Plus, knowing NOTHING about the electrical specs for the fuel pump, that variation may well be within the operating specs as oftentimes the ranges seem to be around + 5 % or even + 10 %.

Now, the fact that putting a different fuel pump in kept the generator running...then that is obviously a good sign. :) Just not so sure you can make that determination from the current measurements.

I hope your diagnosis is correct. Please keep us posted on longterm operation.

~Rick

Rick Jay, I put those amp readings in for a reference.I don't know if they're relevant or not. Electronic problems are my Achilles heel. I fairly well understand mechanics, not so much electronics. I removed this 2nd pump a couple of years ago because I couldn't get the gen to even start. Why it will run with it now, i have no idea,lol. My thought was that the pump was drawing excessive amperage and tripping a self-resetting breaker. It would run for 15 minutes, die, wait 5 minutes, start, run 5 minutes, die, etc. My next option is to go to a repair shop and I hate to pay some one to fix a problem if I can fix it myself. Keeping my fingers crossed for now.

soxbrat,

What brand is your generator? Is it an Onan 5500 or 7000 by any chance? I know that many of these are very sensitive to oil level, and in my case, oil weight. Mine used to shut down frequently while traveling on the road in hot (over 90 degree) temps. I was using the multi-viscosity oil Onan recommended for the temperature range (5W30...I think, but would have to check.). I discovered that the oil level would drop a bit while traveling, so then I got into the habit of checking/topping off the oil level on the generator before and after every trip. That helped, but it would still, on occasion, die...especially after going over a pretty severe bump or road heave.

I switched to straight 30 weight oil (also recommended by Onan) and haven't had the problem since. I know the multi-vis oil was supposed to be as thick as 30W in the heat, but I don't think it was, and thus sloshed around a lot more. That's the only thing I can think of.

I don't know if your issue is related to the oil, but I do know that the oil level shut-off switch on these Onans can be very touchy.

Good Luck,

~Rick

I just finished replacing the fuel pump (and fuel filter). It started and ran fine for 40 minutes with both air conditions as load. When I got the old pump off, there was a bunch of tar-like crud oozing out from the bottom of the crimped end. Something was going wrong inside the pump. Hopefully it's fixed for a while.

sounds like the ethanol in the fuel is deteriorating the fuel lines or the fuel pump.

For future reference. These are for my Onan 5500 generator.

Fuel Pump

Fuel Filter