Onan 5.5K Generator

[10forty2]

Having trouble getting my generator to run. I dove into it yesterday and found that apparently it's not getting enough fuel through to the carb. Disconnected the fuel line, removed the fuel filter...it's open, evidenced by being able to blow through it. Some gasoline blew out of it and some runs out of the feed line, but not what I would think would be an adequate amount. The unit acts like it wants to catch and start running on its own, but it quickly stops when I let off the starter switch. I removed the spark plug, grounded it and hit the starter...good spark, so that's not the problem. I removed the breather and injected a small amount of gasoline directly into the carb and for a few seconds, it runs. Which tells me I have air and spark, but not enough fuel.

So....before I tear into the carb to check for a stuck needle or float, is there a separate fuel pump for the unit or is it simply a vacuum feed? I do not have documentation on it that came with the coach, and can't seem to find any documentation specific to my unit online.

[udidwht]

As for the fuel...Sea foam isn't a fuel preservative. If you plan on storing the RV for several months or more purchase the required amount of Sta-bil fuel treatment for your size fuel tank. Add it then top off RV and drive the RV prior to storage to mix additive in tank and to prime the lines with it. Once done it will keep the fuel fresh for a min. of 12 months.

[wilanddij]

If you eliminate any gas line or filter problems, tearing into the carb is not all that tough. Make sure you get the carb ALL torn down and cleaned. Took me 3 tries before I got all the crud out of mine.

Now I make sure the unit gets exercised under full load for an hour at least once a month like Onan says.

[mci7]

Screwed up, double posted

[mci7]

The biggest problem we see is the unit has sat for a long time, has the low grade (cheap) gasoline and the carb gets fouled up. The solution is replace the carb if you want it to run & act correct. With todays lousy gasoline, the shelf life is short. Once you have a good carb, you can start with the Sea Foam and other cures, agree Sae Foam does have a place.
Over the years you learn to use a higher grade of gasoline with the higher octane, it does have a longer shelf life.
My lawn mower is the only thing I have left that uses gasoline, and it only gets the good stuff, can sit all winter, and starts up in spring like it was just used yesterday.
Good luck
Dave M

[10forty2]

Well, after a little tender loving care, ....and gaining partial access to the carb and gently shooting Seafoam into the Venturi valve with a hypodermic needle and on the choke butterfly and into the bowl via the fuel line..... she's breathing...coughing and sputtering... but breathing. I had to hold the choke closed to get enough fuel into the intake so it would crank, then hold it partially closed for about 5 minutes before the unit would finally run roughly on its own. Still cuts off, and still runs rough, but I think with fresh gas infused with the essence of Seafoam now running through it, the float and needle valve will free up enough to work properly and let her have all the fuel she wants!

Word to the wise...if you ain't using your generator frequently or at least cranking it weekly for 15-20 minutes preventive maintenance, you are creating trouble for yourself when you get ready to actually use it!!!

[allbrandauto]

onan has fuel pump problems easy to check take off gen. cover when gen, shuts off hold down on the off prime position on start switch at gen, you should here a clicking noise to prime carb. if not fuel pump probably bad to check wiring to pump disconnect both wires going to fuel pump get 12 volt test light and hook up between both wires if test light lights fuel pump is bad

[mfox20]

Had the same issue on my 2000 Holiday Rambler Endeavor, 36' Gasser with the Onan 5.5 unit. My issue turned out to be a cracked fuel line from the main tank to the generator.

Easy test is to disconnect the main line at the generator where it enters the fuel pump then hook up a short piece of fuel line and drop it in a gas can on the ground. Mine would run for hours off the can but stop soon after hooking the main line back up.

PM me and I can give you some tips on getting to the top of your main fuel tank to replace the hose at that point without dropping the tank. Your outside compartments should be the same as mine.

Michael

[Gjac]

I would disconnect the fuel line to the carb then hit start switch and see how much fuel is actually pumped out. If it squirts out good before you dive into the carb try some Seafoam in the carb first and see if it starts.

[MountainAir05]

Maybe this is the right one., Yes it has a fuel pump, not vacuum feed if you have the one in the link.

http://www.cumminsonan.com/www/pdf/manuals/983-0501D.pdf

[WyoTraveler]

Onan has had fuel pump problems because of heat. Fuel pump mounted bottom left and it gets hot.

[don_b1]

I would suggest checking the rubber gas line for any signs of old age, crackng, etc. If you are lucky enough to inspect all the way to the tank connection look for any leakage. I would suggest disconnecting at the generator and and hook up a new line and run it to a 5 gallon gas can to check if the unit will run, that will eliminate any gas line problems as far as a faulty line to the tank.

[10forty2]

It is a gasoline unit that gets fuel from the main gas tank for the drive engine. I'll get the data plate information and go from there.

[Matt_Colie]

Doug,

There are three different Onan 5.5 units.
It probably did have a fuel pump - I'll get back to that.
Without knowing the model and the age, that is a stopper.
I am guessing that it is a gas engine because it has spark plugs, but some of the Onan 5.5s are diesel and some are LP.

Collect the data plate and search the web, there is probably a manual -service or at least operators - available somewhere.

If the unit is more than 10yo, replace all the fuel lines and then test the fuel pump. There probably is one, but it may have been murdered by the alcohol that the put in what is now sold as motor fuel.

I have had to deal with this on all of my old generators.

Matt