Re: 1929 640 fuel running out of the carburetor

Posted by DavidM On 2011/3/2 23:28:55

Hank,
If I understand it, fuel is overflowing out of the air vent on your vacuum tank. I had a similar problem once on 1929 633 which has the same fuel delivery system as your 640.
The vacuum tank contains two valves that are operated by the float. When the float level rises it cuts off the vacuum line to the manifold, and opens the air vent so the fuel can flow from the inner chamber to the outer, when the float drops it opens the vacuum line and closes the vent so that the inner chamber is under suction to draw fuel from the tank.
The 2 small valves have half round spherical pieces either side of the lever arms that are soldered in place. One of those came off the vacuum line on mine so that the suction line was permanently open. The same thing may have happened to the vent line on yours although that does not explain why it works on another car
I would take the top off the vac tank and check that the 2 valves are working correctly. The Vac tank is a very simple device.
David