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Oldman5145 · 04-13-2017, 09:19 AM

I have a Onan 5500 gas generator that will randomly shut down. The unit was brand new in my 2017 Thor motor home. Cummins /Onan charged me $600 to tell me it was a tank of bad gas in January. First of April I went on a 2200 mile trip. One day on the road it would not run for more than 30 minutes (full tank of gas ). The next day it ran flawlessly. I think the bad gas excuse is garbage, but I am no expert and I refuse to put another $500 to $600 in something that should be under warranty.
I feel like it may be a weak fuel pump. Anyone have any other ideas?

ModestMonk · 04-13-2017, 10:55 AM

Do you exercise it regularly?

Gordon Dewald · 04-13-2017, 11:07 AM

I had issues with out 5500. Mostly lack of use. I took it to Cummins and they flushed the carb with a product called 4C. They took off the fuel line, dumped out the gas and filled the line with 4C. Then put the line back on and started the generator.

Repeated several times. Ran flawlessly after.

winniman · 04-13-2017, 02:59 PM

If you use regular gasoline with ethanol in it, it also goes into the generator. If you dont use your generator regularly, or exercise it , the ethanol can gum up your carb. I had that problem once with my onan. Took the carb off, cleaned it and all was well. Now at the end of the season as storage approaches, I put the last few tanks of fuel in as premium. This is not supposed to have ethanol in here in Ontario. I also add some fuel stabilizer as well.

**Lt Dan** · 04-13-2017, 03:05 PM

Another possibility is the fuel pump. The 5500 fuel pumps are noted for giving problems. I had continuous problems with the one on my Itasca shutting down with no trouble code until I replaced the pump. You can search on Amazon for the part number located on the pump and find one for less than $40. The pump is located underneath the left front edge of the generator and is easy to change out.

Clay L · 04-13-2017, 03:07 PM

Have you checked the code on the generator stop switch?

vsheetz · 04-13-2017, 06:02 PM

Two problems I had with a 5500 that would intermittently shut off.

1) Fuel pump. It's relatively inexpensive and easy to change yourself
2) The oil level must be up to the tippy top (not just full on the dip stick), else the low oil sensor will errantly shut it down.

I also have paid Cummins / Onan a lot of money for not fixing anything... )-:

raineman · 04-13-2017, 06:21 PM

Sounds like a fuel pump or oil level to me as someone has already mentioned. Very similar to the issues I had. However, I am a bit confused why you are paying anything, let alone $600. Cummings Rocky Mountain here in in AZ replaced my fuel pump under the 3 year warranty (from date of purchase) with no charge for diagnostics and replacement. No issues since

winniman · 04-13-2017, 08:05 PM

I changed out my generator a few years back, and when we put in the new to me generator, it would not run. It had run perfectly when we tried it when we bought it. My friend said to check the ground. We put a jumper cable on the side ground and ran it to the frame ground on the sidewall. Bingo, it ran instantly. Not saying this is your problem, but worth a try. The ground on my onan was only a strap on the back that grounded to the generator carrier, not to the actual frame. We ran a permanent ground and have never had any trouble since.

Oldman5145 · 04-14-2017, 06:24 AM

Quote:

Originally Posted by raineman

Sounds like a fuel pump or oil level to me as someone has already mentioned. Very similar to the issues I had. However, I am a bit confused why you are paying anything, let alone $600. Cummings Rocky Mountain here in in AZ replaced my fuel pump under the 3 year warranty (from date of purchase) with no charge for diagnostics and replacement. No issues since

Thanks to all responses. Cummins Atlantic in Roanoke, VA says that I have water in my gas tank and that is not a warranty item, so they charge by the hour. As far as use I purchased the coach new on May 25, 2016. It had 610 miles in delivery to the dealer. I now have 11800 miles on it. My DW is known to keep things cold enough that we don't really need a freezer, so we travel using the rooftop air. My generator now has over 300 hours on it. The longest it has sat is from Thanksgiving to January. I have changed the oil twice, coach and generator at 5000 mile intervals. I start looking to get gas at a half tank so I never get below a quarter tank and the fuel filter has been changed.
I think that I am going to buy a fuel pump and an oil sending switch. Replace them both and put Cummins/Onan on my try not to buy list. I know that they will never feel it, but I will feel better!

winniman · 04-14-2017, 06:39 AM

Pull off the fuel line and crank it over. If there is gas flying out of the line, chances are your fuel pump is fine. On mine at least the pump was on the generator. If you think there is water in the gas, put some methol hydrate or gas line antifreeze in the tank. You could also try running a line out of a can of fresh fuel to the pump. Good luck. You shouldnt have to pay for such a new unit. Thats not right.

twinboat · 04-14-2017, 07:20 AM

Since the generator pickup is set high in the tank, to run out at 1/4 tank, if you have enough water in the tank to effect it, the engine should be stumbling too.

Have you gotten any check engine lights while driving ?

If not, I wouldn't worry about bad gas, since water settles to the bottom of the tank.

The generator should be saving codes when it shuts down. Look for fuel, oil or overheat.

If fuel, pull off the gas filter and see if you can blow thru it easily, you should be able to. If not, replace it. Otherwise it could be the pump.

If overheating, you may need additional air flow.

If oil pressure, make sure it's full.

Johndale · 04-14-2017, 07:31 AM

https://youtu.be/q3gJvJaBtO8

ga traveler · 04-14-2017, 07:39 AM

We were changing out way to many fuel pumps on the Onan's. I finally got fed up and started researching the problem. I started tearing down the pumps and found almost every one was shutting down because of rust. Rust in fuel is not like what you envision when hear the word rust. It is not long pieces of brown metal. It is like tiny sand, except it is metallic and can be picked up with a magnet. I looked in my Onan installation manual. It clearly states "There must be a fuel filter before the fuel pump to prevent clogging of the pump." Most of the motorhome manufacturers DO NOT install a filter before the fuel pump. My pump failed on my 1998 Pace arrow. My son-in-laws failed on his four winds motorhome. I removed both pumps and cleaned them. Installed a filter before the pump and we have had no problems in 10 years.