On board 5th wheel generator

CEDRICWARD wrote:
To all those of you who have Onan 5500 generators. Or other large ones.
I have one that has been run less than five minutes since 2008. It came with a deluxe toy hauler that was stationary while I had it.
Not knowing how bad ethanol gas is on small engines (and everything else..it absorbs water and when old it leaves a horrible amber residue in your carb which nothing dissolves) I have been learning all about the problems with Onan generators.
First, NEVER leave old ethanol gas in your generator for any period over two weeks. It goes bad very quickly. It will gum up your carburetor (They cost $270 at the least with some asking over $300).
The two metal fuel filters can become clogged with a thin membrane of varnish or residue ethanol like mine did (the one screwed into the fuel pump under the generator where the fuel line enters on the left side near the front by the 12 volt lines was the one that plugged up on mine. The one by the carburetor was okay. The fuel pump filter had a solid membrand over the exit tube going into the fuel pump that looked like looking into a toothpaste tube, but it was just a thin membrane.
I took a pick and got the gunk out of it and blew through it to see it was clear. The filter going into the carburetor wasn't plugged.

I agree with the poster who put a clear filter BEFORE the fuel pump so you can see the gas's color and also make it easier to replace if it's not under the generator (one tech said ethanol gas can corrode the fuel pump too).

It can also rot your fuel lines, so if you have trouble starting your generator you have to check everything from the fuel inlet hose through to the carburetor before you buy expensive parts.

The new carburetors have a metal hard fuel line sticking out of the carburetor where the old second filter was so you don't have to mess with a second filter OR getting an adaptor that threads in to the carburetor if you did have a second filter and removed it requiring an adaptor to put the rubber fuel line back on saving over $18 for the adaptor. If you have a second filter by the carb, I would remove it and get the adaptor so you don't have to hassle with it anymore.

As to a gas Onan or a Propane Onan, my research says that gas is a better fuel for energy output than propane, but with this ethanol gumming up everything and absorbing water and corroding rubber fuel lines, I say STAY AWAY FROM ETHANOL GAS! You can buy non-ethanol gas for about 30 cents more if you can find it.

You can find it using http://pure-gas.org/, Be sure to update the site when you find gas on it as the prices need to be current.

Propane does not put out the energy that gasoline does but it doesn't go bad like this ethanol gas does and you can store it forever.

You should have a SEPARATE propane tank for your generator from your onboard appliances to eliminate any pressure problems between all the devices.

My experience calling the main office of Onan was very poor as Cummins-Onan won't give you any information about anything that is not their equipment due to liability.

I asked about propane adaptors for my gas 5500 and got nowhere with them. It turns out that my unit is the one that no one has an adaptor plate for to adapt to propane so if you are going to buy an Onan, be sure to get the propane model or one that can run multi fuels if they have one, then be sure to never run ethanol gas in it unless it's an emergency, and then AFTER USING GAS clean it out and pump some Seafoam straight out of the can using the rubber fuel line that leads into the fuel pump until you think it has reached the carburetor using your primer button.

I think the generator will actually run on Seafoam ($8 a can now down from $10...get several cans to have available for emergencies and use it in your gas for the generator if you have to use ethanol gas.)

Above all, NEVER leave any gas in your generator or it will cost you dearly for a new carburetor as everyone posting on other sites has had to do in the end after wasting time and energy trying to clean their carburetors. The carburetor CANNOT be cleaned well enough to make the generator run properly and the carburetors are just too expensive.

If you do leave your generator unused for any length of time, pump the Seafoam into it as described. It dissolves everything. Try it on a gas stain on your car fuel inlet to see how quick it works!

If I had it to do over again, I think I would buy that very expensive portable but quiet Honda generator (maybe two of them) as my opinion of Onan generators has been severely degraded from my experience with my unit and their pricing for parts.

Avoid problems and follow my directions or suffer the cost and the wasted time having to fix your generator.

Lack of use may have been your biggest issue. I believe it is recommended to run the unit for an hour or so once a month. If your unit has only been run for 5 minutes since 2008 I imagine you will have problems related to gas and gumming issues.