Vapor lock is a myth, invented by people who don't understand physics and are too lazy to learn. True "vapor lock" is extremely rare, and it's a condition where fuel lines, the fuel pump, and other associated parts get hot enough to boil the fuel, resulting in vaporized gasoline that can't be pumped like a liquid. It has absolutely nothing to do with a refusal to crank. That's an electrical problem you haven't discovered yet, probably a bad ground that heats up and won't conduct enough current flow to operate the starter efficiently. Start by running a heavy gauge new battery cable from the battery negative post to the engine block, cylinder head, or other location near the starter. Be sure to scrape away all the paint, rust, or other insulating stuff down to bare, shiny metal before bolting the cable on. Some people recommend using a copper-based conducting grease on the connections- - - -I've never found a need to do that since I began doing electrical work in the 1950's, if I do the rest of my job right.
Jerry
