[JSeery]

Vapor lock occurs when liquid fuel vaporizes. Many things can contribute to fuel vaporizing. Both heat and pressure come into play. High heat can boil the fuel in the carb float bowl (vaporize it). Low pressure on fuel can also vaporize it. The higher the pump is relative to the fuel tank and the futher it is away from the tank the lower the surface pressure on the fuel will be. That is because the pump pulls the fuel by creating a lower pressure at the pump relative to the tank. This increases the likelyhood of vaporizing the fuel. A pump mounted low and near the tank requires much less pressure drop between the tank and the pump and pushes the fuel under pressure to the carb.