30 according to a first embodiment of the invention is seen in fig2 a 2c valve 30 is positioned in fluid communication with the fuel line between the pump 14 and intake manifold 22 preferably adjacent or in the fuel pump outlet 15 see fig1 valve 30 is a spring biased ball valve which is biased in the open position seen in fig2 a at rest with no forces acting thereon valve spring 32 which is connected to and between valve seat 34 and valve plate 36 biases ball 38 in spaced relation to the valve seat 34 an opening having a spacing u201c s u201d is thus created about the circumference of valve ball 38 in the normally open unbiased condition of valve 30 fig2 b shows valve 30 in the extended open position which occurs when the engine and fuel pump 14 are running and fuel is flowing through valve as indicated by the arrows u201c f u201d the force of the fuel f flowing through the valve causes the spring 32 to extend which increases the original spacing s between the ball 38 and valve seat 34 fig2 c shows valve 30 in the biased closed position which occurs when the pressure in the fuel line downstream of the valve toward engine 24 is a predetermined amount higher than the pressure upstream of the valve toward pump 14 the pressure differential that occurs immediately after the engine is shut off is sufficient to cause the valve 30 to close as seen in fig2 c this will maintain the pressure in the downstream line 20 until the engine begins to cool maintaining the pressure for this period of time is desirable since the pressure prevents the boiling of the fuel in the.