Carb leak from idle adjust screw

[1931 Pick-up]

Hello all!

I have an odd fuel leak from my Tillotson XF carb and might need some assistance. Everything is fine idling before a drive, until after I drive for 10+ minutes and get it hot... Then it sputters fuel from the hole drilled opposite the idle fuel screw. See pictures for precise location - The yellow arrow is where the fuel is coming out, the blue indicates the adjustment screw.

The issue it that after a drive (hot engine) then shut it off, I hear sputtering and a spritz of fuel leaks out and lays on the top of the carb...some even sprays as far as the valve cover. I don't mind losing some fuel, but the obvious concern is fuel landing on the hot exhaust and causing the worst possible!
I plan to tear it down tonight and replace the gasket tonight but I was curious if anyone else had a leak from the same spot and what solution they required.

Thanks in advance!

 

[chap52]

Years ago when learning to fly small planes we would cut off the fuel supply and then let the engine run out of fuel before turning off the ignition.
I hope that the new gasket fixes the issue for you. If not treat it like a Cessna at least until you can solve the problem. Chap

 

[1931 Pick-up]

Years ago when learning to fly small planes we would cut off the fuel supply and then let the engine run out of fuel before turning off the ignition.
I hope that the new gasket fixes the issue for you. If not treat it like a Cessna at least until you can solve the problem. Chap

Actually haven't tried that yet, good thinking! This model A was a gift from my grandfather who unfortunately isn't here to answer my questions anymore. I very much appreciate your suggestion!

 

[nkaminar]

Here is what I think, and I could be completely wrong. The little hole is a vent to keep the float bowl at atmospheric pressure. If the fuel in the float bowl gets to high it can squirt out the little hole.

The fuel supply tubing is not stock which raises some questions about the pressure getting into the carburetor, for instance if there is a fuel pump. If the pressure is too high it can cause the float valve to leak. Or the float valve could be defective or the gasket bad that would cause the valve to leak which in turn would cause the fuel level in the float bowl to be too high. Or it could be that the not adjusted correctly.

Chap has the right approach. The fuel should always be turned off when the car is parked. If it is going to be parked for a while the carburetor should be run dry.

 

[1931 Pick-up]

Here is what I think, and I could be completely wrong. The little hole is a vent to keep the float bowl at atmospheric pressure. If the fuel in the float bowl gets to high it can squirt out the little hole.

The fuel supply tubing is not stock which raises some questions about the pressure getting into the carburetor, for instance if there is a fuel pump. If the pressure is too high it can cause the float valve to leak. Or the float valve could be defective or the gasket bad that would cause the valve to leak which in turn would cause the fuel level in the float bowl to be too high. Or it could be that the not adjusted correctly.

Chap has the right approach. The fuel should always be turned off when the car is parked. If it is going to be parked for a while the carburetor should be run dry.

ah ok, I see your point about the atmospheric pressure vent. With higher temp and no fuel consumption (shut off after a drive) the pressure could increase and exit through there. And yes the fuel system has been modified... there's a tank under the bed and I believe there's a 6v pump somewhere under the frame. Will have a solid peek next time I can. I will definitely try the suggestion of allowing fuel shutoff before ignition shutoff.

It's very exciting to get this gorgeous piece of automotive and family history back to its glory! I appreciate y'all offering your help!

 

[nkaminar]

The Model A carburetors are not designed for very high pressure, only a few inches. You may want to measure the pressure at the carburetor to see what it is. There may be a pressure regulator or the pump may be adjustable or designed for low pressure. Some fuel pumps are designed to stop the flow when they are shut off. If that is the case with your car then you may want to install a separate switch for the fuel pump so that you can turn it off half a minute before you turn off the ignition.

Welcome to the Barn. When you get a chance, post some photos of your car.

 

[1931 Pick-up]

Welcome to the Barn. When you get a chance, post some photos of your car.

Thanks again! and thanks for the warm welcome!

snapped a few the other day when i was working on it. sometime soon I hope to get rubber for the black powder coated wire wheels and get them mounted...havent decided on black or white walls yet

 

[nkaminar]

Nice looking truck. I can see where the gas tank is mounted in back of the cab. That looks like a nice safe place for it.