A fuel leakage prevention system for preventing undesired leakage of fuel into the combustion chambers of an internal combustion engine equipped with a pressure/time, cam actuated unit fuel injection system. The system includes a main housing containing an evacuatable chamber adapted to be connected by a first fluid conduit to a source of sub-atmospheric pressure by a check valve and manual shut off valve. The evacuatable chamber is also adapted to be fluidically connected to a common rail supplying fuel to the injectors by a solenoid controlled valve which is open during engine shutdown and closed during engine operation whereby fuel is withdrawn from the injectors by the vacuum upon engine shutdown.