Carb. Issue

Scottio57

Scottio57

Senior Member
1930 sport coupe. Zenith 1 carb. Been running great. One day on my way to work it would not idle, just died. Would restart and run fine just would not idle. The next day I noticed gas leaking from the adjustable needle and found the float valve would not shut off. I change the float valve from another running carburetor and it started leaking fuel from the small hole on the bottom of the intake throat at idle only. So I toke the float valve out and put it back in the other carb. and changed out the whole carb. Now it runs good and idles good but will not respond to adjustments. Adjustable needle and air mixture both shut off idles great. Open adjuster, no change. Open air mixture screw, no change. Both carbs are clean. I wonder why the original carb. Will run fine but leak gas from the throat only at idle and why the other carb. Will run fine but not take any adjustment?
 
Work on one carb at a time.
Several reasons for seepage, you fixed it with a change of fuel valves. You checked for proper float level?
When you start trying another carb start with a new carb to intake gasket, and
verify you have clean fuel.
Bob
 
Hopefully you have the pencil filter in the gas tank valve.
That's a good start to keep junk out of the valves and carb, even though you have two other factory filters.
 
I found an old thread that explains using multiple sealing washers to adjust float height. I was wondering why there were two on there I thought the last guy made a mistake and I only put one back on. I put two back on and solved my problem. I never heard of shimming the float valve before.
 
Scottio57 said:
I found an old thread that explains using multiple sealing washers to adjust float height. I was wondering why there were two on there I thought the last guy made a mistake and I only put one back on. I put two back on and solved my problem. I never heard of shimming the float valve before.
Click to expand...

I was told this was done to save metal fatigue on the float adjustment point.
 
Sounds like float level too high or float valve stuck
Check for debris in valve and adjust to 5/8 from carbs honed surface to top of float inverted.
If you can put you fingers in the throat when running or even still the float level is either too high, float sticking, or you have a cap or main jet that is loose/cracked, etc. the latter would be more uncommon . There can be more but that's a good start

Larry Shepard
 
Thanks a lot guys. I kept playing with the float level reducing it little by little untill it stopped leaking. Replacing the float valve started all this in the first place. I did not know there is such a difference between valves. I have been a professional mechanic most of my life but this is my first model a. I have had a t for quite a while but these model As are all new to me. Thanks again for all the good advise.
 
Scottio57 said:
Thanks a lot guys. I kept playing with the float level reducing it little by little untill it stopped leaking. Replacing the float valve started all this in the first place. I did not know there is such a difference between valves. I have been a professional mechanic most of my life but this is my first model a. I have had a t for quite a while but these model As are all new to me. Thanks again for all the good advise.
Click to expand...


Scott,
the New viton tip seats do pretty well if the car is used often, if not then not so well. Make sure where the needle contacts the float that there isn't a "dish" in that area. If so a small dremil and polish can help, as sometimes they are bad enough to cause the needle and float to bind a little. I test needle and seats and if they won;t hold vacuum they will leak.

Larry Shepard
 
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