How Do I Repair a Vapor Lock?

by Dwight Malone
rare old car image by pearlguy from

Vapor lock is rare in newer cars because of the modern fuel injection systems but is common in older carbureted cars. Vapor lock is most likely to happen when driving on hot days and in stop-and-go traffic. The constant acceleration and deceleration makes your engine work harder, causing it to run hotter than normal. Excess heat causes the fuel to heat up to the point where it vaporizes in the carburetor, fuel pump or fuel lines. This fuel vaporization keeps fuel from reaching the engine and prevents your vehicle from running.

Step 1

Pour cold water over the fuel pump and fuel lines while the ignition is in the off position. This will quickly cool down the fuel pump and condense the fuel from vapor back to liquid form, eliminating the vapor lock in the fuel pump and lines.

Step 2

Turn the key in the ignition to start the vehicle while at the same time slightly depressing the accelerator. Do not press the accelerator all the way to the floor, as this will send too much fuel through the system and prevent the vehicle from starting.

Hold the accelerator down when the vehicle starts until the engine is running smoothly. The engine will sputter for a few seconds until the vapor lock is cleared from the lines.


  • If you are routinely having problems with vapor lock in your vehicle, wrap the fuel lines leading to and from the fuel pump with aluminum foil. This will help insulate the lines and prevent the fuel from heating up to the point of vaporization.
  • An engine that hasn't been tuned to the manufacturer's specifications will not run properly and could be working harder than it needs to, which can cause it to run hot and lead to vapor lock. It is always important to follow the manufacturer's maintenance schedule.
  • The location of the fuel pump varies from vehicle to vehicle. If you are unsure where your fuel pump is located, consult your owner's manual.

Items you will need

  • Cold water
  • Aluminum foil

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