Onan 2.8 Carburetor Cleaning DIY (no removal)

[dolphindriver]

Let me start by saying I am not an expert on small engines, but I distilled a bunch of information from the web and it worked well for me.

My generator had 14 hours on it (1989) and had not been run in a while. Surprisingly, it did run at first, but I had to hold the choke to make it run. Finally the generator would not start at all. My generator needed the choke on because very little gas was getting through the carburetor and the choke makes it run richer (less air). Any generator that has been sitting or not exercised will have varnish and gunk in the carburetor that keeps it from running - or makes it run rough. You need to clean inside the carburetor on the fuel side. Spraying carb cleaner in the air intake will not work at all.

Here is what worked for me, without taking the generator off the coach or taking the whole carburetor out. Writing it out makes it seem much more complicated than it is.

1. Disconnect the fuel line from the carburetor (it connects the float chamber) and move the fuel filter out of the way as much as possible.

2. Unscrew the brass bolt on the bottom (underneath) the float chamber. The bolt will come out - it has some holes in it and an o-ring. It will probably be gunky. I think it is 1/2 inch or 12 mm.

3. Carefully twist the float chamber back and forth and pull down and it should come out (just a press fit on mine). Don't be scared - it is just one bolt and the float chamber - you don't have to disconnect any linkages or touch anything else. (you will spill some gas if there is some in the chamber - so get some rags under it).

4. Spray the parts of the carburetor you can now see (still attached) with a good carb cleaner (I used "Deep Creep"). I also sprayed up the hole where the bolt screws into the carburetor body. Make sure you get the float mechnism. Spray the cleaner in the fuel line connection as well. Do this a few times to get as much junk out as you can.

5. Take the float chamber and the bolt you removed and soak in a solvent (I used Deep Creep in a very small container). Take the o-ring off first (but don't lose it). I soaked and used paper towels/rags to get rid of all the varnish and gunk. I would let it soak, then come back in an hour and work a little bit, repeat. I was able to clean out the inside of the bolt (hole down the middle and two small hole on the bottom) with just paper towels (you do not want to scratch the inside - but a soft pipe cleaner would probably work great). Take you time and keep letting the solven do the work (overnight is good). Mine was almost spotless when I put it back on, but I still had some rust/gunk at the bottom in one place. Make sure you clean the hole on the inside barrell of the float chamber (I turned that plastic thing both directions with lots of Deep Creep - but then put it back in the position I found it).

6. Once the gunk/varnish is cleaned out of the chamber/bolt - put it back on the generator in the same position it came off. Don't forget to put the little o-ring back on the bolt first. Tighten the bolt down.

7. Get a small container (I used a clean coke can). I filled it with 2/3 gas and 1/3 Sea Foam (or another carb cleaner). You could adjust your ratio as you see fit. Buy 2 or 3 feet of fuel line (1/4 inch inside diameter) and find a small funnel that will fit in the fuel line.

8. Very Important - put a stopper in the fuel line coming from the fuel filter (or otherwise the fuel pump will pump gas over everything). I just used a short stuby philips head screw driver - it fit into the fuel line and I tighted the hose clamp - it held fine.

9. Attached the fuel line you just bought to the carburetor - hold the other end of the fuel line above the carburetor, and (using the funnel) pour the gas/sea foam mixture into the fuel line. You just need to add enough to fill up the float chamber. When no more will go in, carefully allow the extra gas/seafoam in the fuel line to run back into the coke can (put the can and the fuel line end below the level of the carburetor).

10. Move the fuel line and coke can away from the coach for safety. I also let the spilled gas evaporate for 5 minutes. If you are confident, you could probably keep the fuel line attached to the carburetor, but I disconnected it each time.

11. Start the generator - if you are lucky it will run. Let it run until it stops (float chamber empty). Then repeat steps 9 - 11 a few times. After that - let it run for a little while - then stop the generator. This will keep the gas/sea foam mixture in more parts of the carburetor. Let it soak for an hour - then repeat. When you get tired of this - just reconnect the regular fuel line it should run fine from then on out.

11B. If you generator doesn't start - you can try removing the jets from the carburetor and spraying deep creep in there (make sure you count your turns carefully as you unscrew them so that you can put the jets back to the correct depth). I feel that if you tried to run the generator a little bit each hour - with the gas/sea foam mixture in the float chamber - there is a good chance that it would break down the varnish over time and start to run.

12. Pour the remaining Sea Foam and gas/sea foam mixture into the trucks gas tank.

The theory is that varnish/gunk blocks up the carburetor. The carb passages are small - so even if you take if off the whole generator and soak it - you will probably not clean out all the gunk in the small passages. As long as the generator is running a little - if the solvent is in the float chamber it will pass through the carburetor and devarnish the little passages. One guy on the web said he a couple times a day over the whole week on a really bad one and the generator finally ran well.

I was pretty amazed that it worked for me, considering it was not running when I started. Certainly cheaper than $300 new carburetor.

[dolphindriver]

Option 2. If you don't want to take the float chamber off (if you think your carb is not that badly varnished/gunked) you could just start at step 7 in the procedure I laid out.

The theory is to get a high concentration of solvent/carb cleaner through the carburetor. You cannot put that high a concentration in the gas tank of the motorhome, so you need to just disconnect the fuel line from the carb (close off the original fuel line at the fuel filter somehow) and use a new fuel line to pour in a suitable concentration of gas/carb cleaner to get rid of the varnish/gunk. I suggest 2/3 gas and 1/3 SeaFoam or other solvent - people have used lower and higher concentrations of solvent - up to 100 % solvent for a short duration.

Cheers,

[Kim G]

Thanks for this!  I haven't had a chance to try yet, but when I bought mine the owner told me it needed a carb job before the generator would run.  I appreciate the tutorial.