Onan/Cummins 5500 Surging

[Dan Lockwood]

The other day I had to use my generator as the park power was scheduled to be down for a couple hours. Since it was in the 90's I fired up generator to keep it "cooler" inside for the power outage.

Started up and everything was running inside, Good to go.

I had both AC's on for a decent load I would assume, but after about five minutes the generator started to surge in rpms. Quite noticeable.

I know voltage output is dependent upon rpms and did not want to run the AC units in low voltage.

I started it back up a few minutes later and it started to surge again. Kind of like the smaller generators with no load.

Is there a governor adjustment to limit the down side of the throttle to smooth it out?

The generator only has about 14 hours total use since '12.

I have a tach to set the rpms if needed.

Any suggestions?

Thank in advance!

[mybluox]

How old is the fuel? You could have a gummed up carb.

[Texas Steve]

Is it possibly low on oil?

[Dan Lockwood]

Flushed old fuel last August when I purchased the rig and put in new gas and Seafoam. Ran it for couple hours and it was good then. Added Stabil to the tank when I winterized it last winter.

I've used it just a little at home this spring, but didn't see any issues then. I would have to guess has is not the issue.

Changed filter and oil this spring too.

[ChuckS]

https://youtu.be/C6JEiGbR01A

[Frank G]

Change the fuel filter, In the motorhome I blew compressed air through the line to the main tank. It is ok to drop the carburetor sediment bowl and see what it looks like. Is the fuel tank properly vented?

Good Luck

[roadglide]

My 5500 did the same thing . The next day it started good sounded bad . I changed a fuel filter that didn’t help , looking at the exhaust pipe seeing it’s black from running rich , getting to the plugs and pulling the baked on caps will be miserable . Onan recommends changing the plugs at 500 hours mine has right at the hours and 5 years old . The unused fuel is used for the old beater truck. I’m betting the plugs are dirty .