Are you sure it's a fuel problem? The electrical system could also give you the same type of complaint. The immediate restart is a sign that it is likely not fuel-related. With that said, a little about vapor-lock: Vapor-lock is a condition where the fuel boils in a portion of the fuel system, turning into a vapor. The fuel pump is designed to pump a liquid, and cannot move the "bubble", once it is in the pump itself. Normally, when this condition occurs, the removal of the heat from the affected part is the most effective solution to your problem. Vaporization of fuel at the carburetor is often easier to overcome than vaporization at the pump, and can be dealt with by restarting the engine. The crank time will be extended, and may also exhibit signs of a flooded engine. The smell of gasoline is usually very strong when the fuel is boiled out of the carb during extended idling or heat-soak while turned off. Another problem we now have, is that gasoline is no longer formulated for delivery by a carburetor. It is no longer formulated with as good resistance to boiling, because it is kept under pressure in a fuel injection rail, usually above 30 psi. No consideration is given to those vehicles that require "gasoline boilover protection". We must adapt. If your problem is indeed vapor-lock, it is likely due to heat buildup at the fuel pump. In most cases, an electric pump can be installed to "boost" the fuel from the fuel tank to the mechanical pump, and help keep vapor-lock at bay through pressurizing the fuel between the tank and the mechanical pump. If the heat is just too much, eliminating the mechanical pump is the only good alternative. Should the problem be electrical, the first culprits to check are the ignition switch, the grounds, and the connections in the ignition system. On electronic ignitions, failing pickup coils often act in this way.
