Cummins Onan 5500 Generator

The ethynol based fuel has very little shelf life before it starts breaking down. Additives help but pure gasoline is better at sitting. Mine was run twice a month and didn't have problems but my lawn mower became an annual carb cleaning affair even after running out the gas at the end of the season.

Finally got my generator fixed. I took it in to Cummins and they replaced the carb under warranty and also installed a shutoff valve so I could run it out of gas (just like we used to do with our motorcycles) while storing it. I still don't understand how the carb could have gone bad in 4 short months. Glad it got fixed.

Wow... that is the cleanest generator I have ever seen!!!

Bedlam wrote:
Picture linked here:

First off let me say I am a bit EMBARRASED. Secondly, the generator still doesn't run and I plan to take it in as it's under warranty.

The reason the fuel went from 3/4 to empty wasn't due to a fuel leak. I hit the battery disconnect. That cuts the power to the gas gauge and that's why it went to EMPTY. I didn't realize this until I pulled the disconnect switch back out to allow power to the trailer. The gas gauge went back up to 3/4.

I am VERY sorry for sending you all down the wrong path. I hope it will be helpful to someone.

I will report back after I get it back from the dealer.

dieseldan723 wrote:

So the reason fuel is coming from there is that the carb is gummed up? How could that happen in 5 weeks? I ran it after Thanksgiving for 30 minutes!

Just because you got this TH 5 weeks ago doesn't mean that was the first time fuel was in the genny, its a cumulative effect. Could also be as simple as a defective/damaged carb.

Good points by Bedlam, imo, take his advice...

I agree 110%, you should without a doubt bring it in if it is under warranty... why wouldn't you...???
Especially with the other problems that might arise from the flooded engine. Check your oil, see if it smells like gas, but don't do anything before bringing it in for warranty repair. Couldn't hurt too, if under warranty, to document this repair by an authorized Onan repair shop, for possible related future problems.

jmo

As it has already been said individual parts are not available, Cummins solution to carb problems is replacement. All is not lost, I have rebuilt ( mostly cleaned/removed varnish) several with great results. I believe the port in the picture is the vent for the fuel bowl. A misadjusted or stuck float would be a possible cause for the bowl overflowing. This carb has tiny passages that can be a challenge to clean/clear. At this point you have a couple of choices, pull the fuel bowl or as Beblam already suggested, take it in on warranty.

Bedlam wrote:
Picture linked here:



You want to be careful about letting gas flow around like that. If it washes down the cylinder walls, the rings will have no lubrication and scratch up the surface. Check the oil level - If it is higher than normal or the oil smells from gas stop attempting to crank the generator.

I have had good luck with carburetor cleaner and compressed air to clean out gunked carburetors. I will spay cleaner through each port and follow with compressed air. Any pieces that can be removed are pulled and inspected for blockage. It's a good idea to snap pictures as you go through disassembly so you can refer back to them when putting it together.

Since yours is still under warranty, I suggest you take it in before any damage results.

So the reason fuel is coming from there is that the carb is gummed up? How could that happen in 5 weeks? I ran it after Thanksgiving for 30 minutes!

Picture linked here:



You want to be careful about letting gas flow around like that. If it washes down the cylinder walls, the rings will have no lubrication and scratch up the surface. Check the oil level - If it is higher than normal or the oil smells from gas stop attempting to crank the generator.

I have had good luck with carburetor cleaner and compressed air to clean out gunked carburetors. I will spay cleaner through each port and follow with compressed air. Any pieces that can be removed are pulled and inspected for blockage. It's a good idea to snap pictures as you go through disassembly so you can refer back to them when putting it together.

Since yours is still under warranty, I suggest you take it in before any damage results.

I took the cover off today and primed the pump. Within seconds fuel was pouring out of the air filter housing. I took it off and the filer was soaked with gas. I hit the PRIME button again and fuel was spitting out of a small opening. Please see this picture as I have highlighted where the fuel was coming out.

picture

Thanks for the above information about the filter. Although I no longer have my 5500, I also had a failing fuel filter in the generator compartment about two years into ownership. After that, I started replacing both of them annually but never bypassed it. I never had a repeated problem with filters and assumed that one was faulty or I had left it too long without replacing it.

Annually, I would clean the air filter (never had to replace it), replace the oil, oil filter and two fuel filters. The spark plug was also still original after 7+ years of use, but I did carry a spare air filter and spark plug with me.