Automobile Fuel-System Design and Vapor Lock

TEMPERATURE rise in the gasoline as it passes through the fuel system is the important factor in vapor lock that is within the control of the car designer. Gravity and vacuum-tank feed systems are considered briefly, including tests showing that weathering of the gasoline in the vacuum tank consists largely in removal of propane.

Vapor lock in a pump system is most liable to occur on the suction side, because of the difference in pressure. Increasing the capacity of the pump for handling vapor offers little relief. Evidence is presented to show the gain made by locating the fuel line where it is protected from the heat. One example is cited to show the advantages of keeping a large flow of hot engine oil away from the pump. It is advantageous also to locate the pump where it will be cooled by the air entering the engine compartment of the car.