A fuel system vapor lock is when the fuel in a vehicle changes from a liquid to a gas state while it is still in the fuel lines. If the fuel is in a gaseous state in the fuel lines, the fuel pump can't push liquid fuel to the engine.
Continue ReadingA vapor lock is typically caused by the fuel overheating somewhere in the fuel delivery system. The problem is most common on gasoline powered carbureted engines that have a mechanical fuel pump in the engine compartment. Excessive heat due to weather conditions, engine overheating or high-altitude driving, which reduces the boiling point are common causes. Gasoline with a higher ethanol content is more volatile and can be a contributor as well.
Vehicles affected by vapor lock tend to run roughly, sputter and die. Typically, the engine doesn't start until it has cooled down. Fuel-injected vehicles with an electric fuel pump located in the fuel tank are less susceptible to vapor lock.
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