onan generator

grinder613 wrote:
I know changing the filter is probable the most important but Ive been under there and traced the fuel line back to the tank (thank you coachmen)and the only filter I can find is the tiny one in front of the pump which is buried next to the genny motor. would have to pull the genny to get it out. ouch. Will try the diluted seafoam before I do that.

I think you should be able to unhook stuff to get at the fuel pump and filter without dropping the generator. It involves removing the starter solenoid and the voltage regulator/electronic control modules, and groping around in some tight quarters, but I would do that over dropping the generator. At least in my case, I had to remove all these bits anyhow before dropping the generator to disconnect the AC output lines, whose wires appeared to be too short to drop without first removing them.

Regardless, if a seafoam treatment works for you, so much the better.

You will probably have a dirty carb. If you think it's the fuel filter open the fuel bowl drain screw while the generator is running you should have a solid stream of gas if you do and it continues to run you don't have a delivery problem. You can get those carbs fairly cheap.
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I know changing the filter is probable the most important but Ive been under there and traced the fuel line back to the tank (thank you coachmen)and the only filter I can find is the tiny one in front of the pump which is buried next to the genny motor. would have to pull the genny to get it out. ouch. Will try the diluted seafoam before I do that.

There are a couple of possible culprits that are easy to check and fix.

If your gas is down around a quarter tank or so (or lower), it may not be getting good consistent fuel flow from the tank. The solution is obvious in this case—buy more gas. Likewise if it hasn't been run for a relatively long time there may be air in the line from the tank to the generator causing it to surge for a minute or so—the problem should clear itself up of its own accord in this case.

A dead or dying fuel pump or a binding/dirty governor linkage can also cause surging/hunting. Presumably a quite dirty fuel filter could do the same thing.

Probably the most common cause is a gummy carburetor, unfortunately, from what I've gathered.

Use the forum search feature - hundreds of post on how to clean carbs with Seafoam.

You may get some play on your question if you "Notify Moderator" and ask this thread be moved to Tech Issues. Update your information to include the full Model Number, all the way to the Spec Code which is the last letter in the Model number.
Often the OP doesn't provide enough detail (mostly full Model Number) for a tech to provide detailed help. There's a crowd of techs at smokstak.com and you can ask for help there also.
If it's running relatively well, you can change Filter and run it with fuel heavily dosed with SeaFoam, Berryman, other cleaners. That MAY do it. Some have dismantled and soaked the carburetor. I've heard of filling the inlet hose with SeaFoam/Berryman. Then start the genny and shut it off for a couple hours. Repeat. The idea is that you're running heavy concentration of cleaner without having to go to the separate tank or dis-assembly processes.
I couldn't get ours right and was very blessed to obtain a good used carb from a genny with a blown engine. Now, I add Stabilizer (Sta-Bil) to every fillup and exercise the genset regularly.

Tech Issues is the place to ask generator questions.
But lots of questions about generators get answered here in Class C.
If you do not get answers you need I can move thread to Tech Issues.

Change Onan fuel filter. Use 1 gal gas can. Add at least half of a can of SeaFoam. Disconnect fuel line to genset stick in can and run til empty. Also some carb spray now and then will keep it running smooth. Onan carbs are Expensive. Also exercise that genset every month for an hour or two with at least a 50% load on it.