Onan Generator Fuel System Flush

Number 1 Most Common Problem – In all our years of dealing with Onan generators that won’t start or run well, the most common issue was that the carburetor or fuel injector was clogged with varnished fuel.

Unfortunately, in this unit below it usually means that the carburetor needs to be disassembled and properly cleaned or replaced.

Here we are attempting to perform a Onan carburetor fuel system flush to clean out carburetor. This treatment typically takes about 1-3 days of setting and soaking and running sea-foam through the fuel system.

For details on how to do this procedure please see Onan or Sea Foams website.

Unfortunately due to the age and gum this service was unsuccessful. Will have to contact customer to advise generator will require a carburetor replacement. Below is the auxiliary gas container used to flush the system with the Sea Foam and fuel mixture.

Auxiliary Gas Fuel Container

I can’t tell you how many times people have said that they removed the air filter and sprayed carburetor cleaner into the carburetor but their engine still doesn’t run well. I’ve never actually seen this strategy work, and yes, we have tried it many times over the years.

Generator maintenance is key to saving money and down time at the shop

The reason this doesn’t work is because there are tiny passages that fuel needs to be able to pass through that are usually clogged with varnished fuel. Simply spraying the cleaner into the carburetor won’t clean these passages.

Running mixture of sea foam through system to flush and clean the fuel system

A carburetor is a very sensitive part of your engine and it isn’t something that you can “get close enough” when you’re reassembling it. It MUST be reassembled very precisely. (Which we don’t offer at California RV Specialists) It’s very labor consuming and very easily to damage small carburetor parts.

In most cases the carburetors are no longer available due to the model or age of the unit. The amount of labor it costs to rebuild the carburetor in most cases exceeds the cost of just replacing it with a new carburetor.

We recommend that you operate the generator at least once a month under a load. (Running the roof air conditioner.) we also recommend that you add some fuel stabilizer to protect system. I hope this helps you understand how important it is to operate the generator regularly under a load and stay up on your maintenance.

More from Dustin

Dustin owns and operates California RV Specialists, an independent RV repair shop located in Lodi, CA. He thrives on sharing his knowledge and enthusiasm of RV repair and maintenance with his team, customers, and virtual friends.

Be sure to check out his YouTube channel where he shares what’s going on in the shop and the product offerings in the store. Dustin is also very active on Facebook. Join his group, RV Repairs and Tips – What’s in the shop

Dustin proudly operates the business alongside his wife, Ashley; but the true pair that run the show are their Boston Terriers, Arvie and Hitch.

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California RV Specialists