Onan AC Generator Wouldn't Start

by Don Archer
(Peachtree City GA)

My Onan AC generator would not start, and I knew that it was a gasoline problem. I tried starting fluid which caused it to run for a few seconds and tried carburetor cleaner which didn't do any good. I made an appointment to have the carburetor replaced on this Genset for a charge of $500. Fortunately the snow storm hit Atlanta the day I was supposed to take it in.

I decided to try one more time and removed the gas line going to the carburetor on this AC generator, held it upside down, and drained as much gas out as possible. Then I sprayed straight carburetor cleaner into the line and reconnected it to the carburetor.

After fighting this problem for a couple of months, the AC generator started right up. I let it run with a couple of bottles of SEA FOAM added to the gas tank. This genset has been starting right up and running great ever since. Hope this helps somebody else.

Editor's Note:

Don is to be commended for his persistence and diagnostic skills. This genset is probably one of the most temperamental systems on a Class C Motorhome. I'd like to add a few thoughts here because I feel that with a little additional information, an issue like the one in Don's story can be easily avoided. Having said that, here goes... all gensets need to be babied for two big reasons:

1. Exercise

Onan recommends that their generators need to be run at least 2 hours each month at 50% capacity. Unfortunately, not running your AC generator can cause a buildup of gum or varnish type substances that can, over time, block the small orifices in any carburetor. This will potentially prevent your genset from starting. It can also make the system run rough with a surge effect. Don was correct in first assuming that his carburetor was the culprit with his malfunctioning generator.

2. Ethanol

The E-10 fuel we use today is hygroscopic. This Ethanol fuel tends to suck moisture out of the air and deposit it at the bottom of our fuel tanks. Of course, this is precisely where our fuel pick-up is located.

Water in the fuel line is a major reason many lawn mower motors do not start in the Spring. Folks, when you boil it all down, your AC generator is just a big lawn mower engine. Water in the line could have easily have been Don's issue.

There are a couple of things you can do that will inhibit this scenario, but I'm only going to recommend one. Keep your tank full when you are storing your Class-C-Motorhome. It is important to understand that Ethanol cannot absorb moisture out of the air if it isn't in contact with air. A full tank will prevent this type of contact.

Again, I want to thank Don for bringing this important subject to our attention...