Onan 5500 gummed - fixed!

[roam1]

I think I dodged a bullet today! My 2010 Onan 5500 HGJAB with 1000 hours finally got the often talked about dreaded gum up 😞 It would start but under load it coughed, spit, and died).

It has worked flawlessly for 5 years, probably cause I used it a lot. This is the first summer I left it in the Florida heat unattended for 3 months.

I took the carb off and hit it inside and out with Gunk carb cleaner. I sprayed every orifice I could find. I opened the bowl drain and half filled the bowl and tightened the drain screw. I reattached the carb and before attaching the fuel line, filled it with an ounce of sea foam. When it was all back together I hit the prime button for a while to force the pure sea foam into the carb. I let is soak for a few hours and then started it up. Was a little rough at first and then smoothed out. Turned on one AC for 5 minutes and then the second AC was turned on. She's purring now! From all the horror stories I've read about the Onan 5500 I feel I cheated death (of a carburetor)! 🙂

[Dusty_R]

wilanddij wrote:
I had to go through the Onan carb gum-up and cleaning exercise when I couldn't be around to start and run it every month, so I installed a shutoff in the fuel line. When I put the RV away this year I ran the generator till it died from lack of fuel. I'm anxious to get back and see how it starts and runs.

I put a switch in the wire going to the electric fuel pump, then do the same as you. Has worked for me for the past several years.

Dusty

[MEXICOWANDERER]

Please post a follow-up because what you did is popular with some folks 🙂

[wilanddij]

I had to go through the Onan carb gum-up and cleaning exercise when I couldn't be around to start and run it every month, so I installed a shutoff in the fuel line. When I put the RV away this year I ran the generator till it died from lack of fuel. I'm anxious to get back and see how it starts and runs.

[edatlanta]

I use non-ethanol gas in my 5500, treat it with StaBil Marine formula all the time and run it under load for 1 hour/month. It currently has 250 hours on it and has never failed or had any problems for a bit over 5 years now.

When I do have to use gas with ethanol I still treat it with Stabil Marine, but make sure I run it all out before refilling the tank with non-ethanol.

Works for me.

[westend]

If you treat your generator gas with fuel stabilizer, you'll have a lot less trouble. I use Stabil for my small engines and don't have many fuel related problems. I just pulled two string trimmers out of storage. They hadn't been used in quite awhile. The gas lines were rotted into pieces. A carb cleanup, new gas tubing, and some fresh gas got them going.

[Golden_HVAC]

Thanks for this report. Fuel can evaporate inside the carb when it is left in warm weather, leaving behind some gunk. I probably will need to do this to my motorhome generator. Last time I used it was back in 2008. So I have a feeling that it will take a carb rebuild to fix it. .

Fred.

[roam1]

gbopp wrote:
Thanks for the report.

Don't forget to change the fuel filter.

Where is the fuel filter? and why does my operation manual say it has to be replaced by an Onan mechanic???

ok, found it in the parts diagram, underneath....

[gbopp]

Thanks for the report.

Don't forget to change the fuel filter.