Surging Onan

550Doug · May 5, 2013

I have an old Onan, 2cyl about 20 hp, that has worked fine for years. This spring it has begun to surge while idling, but under load it runs very smoothly. Is there some kind of adjustment that is out of whack?
Ideas?

David G · May 5, 2013

Open up idle mixture 1/2 turn and see.

DoubleR · May 5, 2013

A good dose of Sea-Foam has straightened allot of carb problems I have had. Especially with my two generators that sit idle for long periods of time.

Anonymous-0 · May 5, 2013

Try to pull the choke on and see if it stops. My guess is the idler jet is dirty.

Texasmark1 · May 6, 2013

I have an aux power unit that does it unloaded. I too think it is the governor searching as it was probably designed to function under load.....just like gas cars used to be.....at idle they would miss, put a load on them and it would stop.

On my unit I just pull flip the choke around to the first notch back from wide open and it solves the problem.

On yours, since it didn't do it before, I'd go with the SF (great stuff for internal combustion engines) and maybe take the cowl off and shoot some aerosol on then linkages of the governor.

Mark

gab · May 6, 2013

I don't know what you mean by old but I've got two of the Onan Perfomer series engines P18 and P20 and both of them do that about every other year, especially shortly after changing an air filter. I think it's a piece of dust gets in an air bleed in the carb. top. All I do is remove the air cleaner top and the round plastic piece over the carb. and spray carb cleaner around in there and blow it out with air. It has always worked for me.

Surging Onan

550Doug

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David G

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DoubleR

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Anonymous-0

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Texasmark1

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gab

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