Vapour Lock generally occurs when the fuel inside the fuel delivery system overheats and vaporizes rapidly, the resulting excess gas bubbles accumulate to a level that blocks normal fuel delivery. Vapour lock is caused in warmer temperatures as the fuel can vaporize in lines when it receives heat from the engine, exhaust and/or outside temperature. High altitude and other factors can lower the fuels boiling point, leading to vapour lock. Vapour Lock is a modern problem, since fuel was designed for modern fuel injection systems, Fuel-injected engines use a more volatile fuel that is easier to vaporize and mix with air for a much better combustion. So this new fuel has a lower boiling point, this vaporized fuel can cause back pressure in the fuel system to prevent fuel from reaching your engine, this happens when the motorvehicle is idling or when it has been turned off and back on. Vapour locks are prevented in modern engines because of the use of an in-tank, electric fuel pump. This