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Tecumseh 12hp 632235 carb flooding


Mad Max's Avatar
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06-14-09, 07:48 AM   #1  
Tecumseh 12hp 632235 carb flooding

Howdy folks
okay, so I picked up a used Murray 12hp/38-inch riding mower, been sitting for years, plenty of varnish in the carb, etc etc etc.
RnR'd fuel line, new battery, attempted start, and to our disbelief it magically fired up . That was great 'n all and it wasn't running great...but it was running. It surged a lot and obviously was fighting 'old fuel' issues. Pulled the air cleaner and noticed fuel pooled up along the bottom of the intake and carb venturi - way too much fuel, leaking from somewhere. Wasn't leaking externally tho. Now I thought bad float or float issue. I know what a Holley or Edelbrock is supposed to look like and which parts go inside them, but not a Tecumseh - this be a first-timer.
Okay, so pulled carb apart, cleaned/blew it out, reassembled, and when fuel line reattached fuel started seeping out the venturi...from "somewhere". I thought the float was bad - pulled and tested - no fuel inside the float, and it floats without bubbles - float is good. Checked the needle/seat - both good. With the bowl off, fuel line connected, fuel will just dribble right out like it should and if I gently hold up the float fuel will stop - needle/seat are working fine. But, install the bowl....fuel leaks up/out...aparantly via the power screw (......)...and starts to fill the venturi.
Okay, so maybe the bowl itself is obstructing the float from moving, so I pulled the bowl, cut the bottom from a beer can, held my simulated float bowl up and watched fuel fill up the 'bowl', and the float bobbed up and...fuel stopped.
Okay, so then I placed a bit of towel in the bottom of the bowl forcing the float up a bit...watched the float come up at I reattached the bowl, inserted the power screw assy...attached the fuel line...and here comes the fuel out the venturi like before.
Okay, so the float is functional, but when the bowl is bolted up fuel leaks out the power screw. Now after searching the web for any good pics of the power screw I still don't know what the power screw is supposed to look like fully assembled, nor do I know exactly how it works, but I'm thinking the screw is either missing an o-ring or something like it and that is allowing fuel to essentially by-pass the float bowl and drain right up and out the venturi without giving the float a chance to do its job. That jibe with anyone? I don't want to replace a whole carb if there's a $.02 o-ring causing the problem.

The power screw assy (and repair kit) looks like this:
632235 Tecumseh Carburetor Repair Kit

The power screw has two threaded portions on it that screw up into the venturi base, and between the two threaded areas is a suspicious gap area, and my big question is this - is that gap supposed to have an o-ring in it? If not, then is it a typical issue for fuel to leak into the venturi via a jacked up power screw regardless of the float doing its job?

Thanks for your thoughts folks,
- Sam


Last edited by Mad Max; 06-14-09 at 08:08 AM.
 
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Mad Max's Avatar
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06-14-09, 01:52 PM   #2  
I think the o-ring is installed inside the power screw/bolt and apparantly seals off the mixture screw which is inserted in the bottom of the power screw. So maybe the o-ring is missing or disentigrated and is allowing fuel past the mixture screw, flooding the carb. Thoughts? I'll check to see if there is an o-ring inside the power bolt tonight when I get home, but I still don't have confirmation that it's supposed to be there in the first place...anyone???

 
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06-14-09, 08:00 PM   #3  
The only thing that can allow fuel to come up there is the needle and seat not sealing off the flow of fuel. Take the float off and hold it near your ear and shake it. If you hear something sloshing in it, it is bad. Replace the needle, seat, and float, all total less than $10.


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Mad Max's Avatar
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06-15-09, 04:26 AM   #4  
well like I said earlier, I checked the float - no sloshing, no bubbles. I checked the float action and needle and seat - all work properly. It all changes when the float bowl is bolted up with the power screw.

Within the power screw, if I tighten the mixture screw in until it stops, fuel will stop overflowing (and then the engine won't run). If I crack it open a bit, fuel will overflow up through the venturi (and the engine will barely run poorly).


Last edited by Mad Max; 06-15-09 at 05:57 AM.
 
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06-15-09, 06:15 AM   #5  
You need to take apart the carb again and soak it. Your problem is "plenty of varnish in the carb, etc etc etc."
You need to soak it in a carb cleaning solution and then use NEW parts. Your needle seat has varnish on it. You also said that you "cleaned/blew it out". If you blew air thru the gas line inlet, you blew out the seat, which is why it is flooding.

 
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06-15-09, 09:48 PM   #6  
Verify that the bowl vent is working. If so, replace the needle and seat.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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