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Sandpirates2 · 01-10-2012, 11:15 AM

Hi,
I have a 2008 Weekend Warrior 37ft 5th Toy Hauler. Due to being sent out of the country for work, my hauler set for about 6 months with nobody running the Onan 5.5KW monthly as I typically did. So, I have replaced the house batteries, removed and cleaned the carb, ran the prime into a container for about 2 gallons and replaced the plugs. Before all of this, the unit turned over but would not even try to fire. After all the above being done once primed the unit will fire up but will only run if I hold down the butterfly valve (Choke). It will run what seems forever with me holding the linkage forcing the valve 2/3 of the way shut.

Once I take my finger off the linkage, the butterfly opens, the unit acts like someone hit the stop button almost instantly and stops.

While cleaning the carb, I open everything and sprayed it with Carb Cleaner, but I didnt remove the jets, sprayed them like crazy in position. I did remove the float bowl, cleaned the float, and also the sensor that comes through the bottom of the bowl (Not sure what that does, but when disconnected the engine will not start period) so I figured its working. The prime works (pumps fuel when pushed) but the unit seems to be running out of gas once I let the butterfly valve open up.

Any help would be appreciated.

Sandpirates2 Mike

Mike Canter · 01-10-2012, 01:05 PM

That is an indication of a blocked main jet or incorrectly adjusted mixture screws. The choke enricment circuit is suppling the gas. Does it have none, one or two mixture adjusting screws and did you remove those or turn them. Normally in the down tube going into the middle of the bowl is a series of jets (inside) did you remove those and clean them. Are they all back in the same position they came out?

Sandpirates2 · 01-10-2012, 02:25 PM

Thanks Mike -

No, in my past dealings with Carbs, I learned not to touch the jets or air/fuel mixture, and as such, they may still have junk in them as I only sprayed them in place, and although I took the Carb apart, these two things I left in place. If I were to take them out to clean, I'm assuming that it would be the "mark and count turns" to ensure they are back in the same place.....??

Thanks
SP2 Mike

Mike Canter · 01-10-2012, 05:05 PM

On those idle adjustment screws yes turn them in while counting by half turns until they just barely seat. Then you can take them out. I was thinking and the other possibility is a major air leak between the carb and the manifold such as the gas in upside down or backwards so not all the holes line up or a hose for a crankase ventilation sysem cracked or not all the way on. Hold ing choke on would cut down some of the airflow to make up for the other air leak.

Dunner · 01-10-2012, 05:49 PM

Even if the main jet was plugged, it should still run off of the idle circuit. Count the turns, remove the idle screw and blow carb cleaner in the hole. If you do this with the float bowl removed, you should see the CC coming out of another hole. If you do, blow out that hole with CC.

Dunner · 01-10-2012, 05:58 PM

If that doesn't work, you may have some hardened varnish that even CC won't break through. Take a single strand from some stranded of copper wire and probe all the orifices and passages. The copper is soft enough to not harm anything.

bbeane · 01-11-2012, 03:49 AM

Sounds like to me the main jet is stopped up (the one in the bottom of the carb). It is easy to remove with the carb off. The hole/holes in the jets are very small and easy to stop up, as O/p said use a small wire or needle to clean them, it takes very little blockage to create the problem you have.

Sandpirates2 · 01-11-2012, 09:12 AM

Thanks - I'll give this a try. On the removal of the jets - do I have to worry about "Turns" or is it like my old holly carbs that you just go all the way to the stop when installing?

Thanks
SP2Mike

Mike Canter · 01-11-2012, 09:22 AM

You only need to worry about turns on the idle mixture adjust screw

Clay L · 01-11-2012, 03:35 PM

Something similar happened to me last year when I wasn't able to run mine for several months. If you don't have an air leak (I didn't) you might try running it for several minutes or so several times. That's what I did and it gradually started running longer and longer after I released it from choke until it ran okay.