Carburetor Problem - Need Help

Bob Grieb

Bob Grieb

Senior Member
I am unable to determine why the shut off valve will not stop the flow of fuel inside the carburetor.

I had the problem when I first installed the Zenieth carburetor and after not being able to resolve the problem I purchased and installed a new valve. I checked the float and it is free of liquid (it floats ).

I bought a sight gage to check the fuel level. When I first turn the shutoff valve at the tank on to allow the flow of fuel the fuel level in the carburetor is about 5/8 inch below the gasket. After about sixty seconds the fuel level rises to the gasket level and fuel begins leaking from the carburetor.

The carburetor is clean as well as the fuel being supplied.

Any help in resolving the problem would be appreciated.

Thanks
Bob
 
Hi, you should be using a VITON needle and seat valve. When adjusting the fuel level (about) 5/8" is not good enough. You can also adjust the float by turning the carb top upside down and adjusting the float parallel with the gasket surface. This information is in the carb repair kit. Hope this helps. Jim.T.
 
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Take old valve to your hardware and they will have a perfect fitting needle type valve for your "A." Mine only cost $3.89!
Stock Model A valves would be better suited for a beer keg.
 
Make sure all the surfaces are smooth and flat with regard to the float. Also, make sure it isn't really close to the bowl sides or something. It seems like it is not smoothly closing. If the valve is new, and works properly then it has to be something else. I agree with the 'level' float when it is closed and upside down. This is only true if your float is un-bent where it touches the needle. I did this, and the distance from seam to seam was extremely close to 5/8's...within 1/32 and mine runs great. I understand the ball valve works better, but I'm using the needle valve with fine results because it is what was there and newish. Good luck..
 
I prefer the Grose style valve.. If the needle has worn a dimple in the float arm it can/should be sanded smooth.. Has the float been previously repaired [soldered]?? If it has, it may be too heavy.. Also submerge the float for awhile just to make sure it isn't leaking.. All the other info is good..
 
:(I just rebuilt and installed my Zenith carb. Before assembly I checked the top section attached to a glass jar with gas line attached to a remote gas system. The level stopped at 5/8 inch from top. The float held at that level overnite. Also checked the bowl for leakage with gas in bowl 5/8 from top.No leakage at the main and cap jet bases, Bottom drain nut or the GAV nut. However when I reinstall carb run engine and then turn off gas flow at the tank, the bottom of the carb will continue to stay moist with gas seepage for hours. Not leaking enough to drip,[ evaporating] but it definately stays moist.
Could this be coming out the top of the cap jet? When looking down thru the throat after assemby and off vehicle I can see gas at the top of main and cap jets but no leakage there after observing off and on for several hours. Anyone have a suggestion for my dillema other than buying a new carb.
Warren
 
Thanks for all the good information. I will take another look tomorrow and see if I can resolve the problem

Thanks

Bob
 
Possibly the valve is not tighten enough on the gasket. Do you have more than one gasket under the valve? If you have gas at the tips of the jets, they are either to short, or the gas level is to high in the bowl. Or a combination of both. Check the book for the correct height of the jets. It is easy enough to measure. Do the jets have the tops, looking like they were drilled out some, or are they raised up or flat? The two jets should look like they were drilled down a bit. This helps them to not weep and also helps the air suck gas from the jets, and make a better blend of air and gas.
 
Ford Fixer; When you say the valve is not tight on the gasket, are you talking about the float valve? If so ,It is tight .Do you recomend another gasket under the valve to lower the gas in the bowl some. The main and cap jets are the right lengths. The cap jet is concaved at the top main not so much. Should I add another gasket to them both to raise them more? Still cant understand why no leakage was found when testing them seperately. The leak is apparently in the lower part of the carb though, seeping out the weep hole. I can feel the moist gas when i stick my finger in under the choke plate.
Warren
 
The float valve gasket could be to thin. I fine them in many different sizes. When setting the fuel level, I remove the float valve gasket and measure the thichness with a veneir calipir. Depending on which way I want the float adjusted, I go with a thicker or thinner gasket under the valve. I never use the white plastic gaskets. They squish down and don't stay sealed like the red fibers ones. I don't like to bend anything on the float. I always straighten the tabs so they are straight. I have found some gaskets at 25 ths. and others as thick as 64 ths. So I never throw these away. Never no when they will be needed in another carb that I will rebuild.
 
Did you do what ford fixer said?.Mine leaks at the drain hole.Can't seem to stop it.?I will try his Idea. I'm with you on the valve shutoff. Shutoff it should!
Good luck,Art
 
Did you do what ford Garage said?.Mine leaks at the drain hole.Can't seem to stop it.?I will try his Idea. I'm with you on the valve shutoff. Shutoff it should!
Good luck,Art
 
I have found that old, hardened gaskets can cause some leakage, so I always use new one throughout. Also, while the main and cap jets may be the right length, it is important that the tops of them also occur at the same 5/8" level as the float when it is at its uppermost position. (See diagram in Les Andrews's book, vol. I).
 
You may have the correct length jets, but, if the gaskets are to thick it will lower the jet that goes in the bowl from the bottom. Now it is not high enough into the venturi. It could also be just at the level of the gas in the float portion of the carb. If so, it will weep. The jet itself could also be cracked and this would then weep no matter what you do. Buy a new set of jets, flow test yourself or have someone in your club do it. This should stop any leakage. Hope this helps. Jon
 
Thanks for all of the response. With so many unknowns about my carburetor I ordered a new rebuilding kit from Snyders today. I will update this post when I get the rebuild complete.

Thanks

Bob
 
Bob, if someone in your local club doesn't have a flow tester, you can also just check the apertures in the jets with some numbered drill bits to make sure they're within recommended tolerances. Les Andrews's book tells what size drills to use, but if you don't have that, post here again and I can give them to you. I don't have a flow tester but I have found that the drill bit measurements serve me well.
 
700rpm said:
Bob, if someone in your local club doesn't have a flow tester, you can also just check the apertures in the jets with some numbered drill bits to make sure they're within recommended tolerances. Les Andrews's book tells what size drills to use, but if you don't have that, post here again and I can give them to you. I don't have a flow tester but I have found that the drill bit measurements serve me well.
Click to expand...

Thanks - I have the Les Andrews manual and I did read the drill bit information. Thanks Bob
 
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