It is common to employ umbrella-type check valves in an impulse fuel pump typically used with conventional two-cycle internal combustion engines. During operation of such engines, variations in operating speed and throttle condition produce generally corresponding changes in the pressure of the gaseous components of the fuel and air mixture within a crankcase. It is understood, of course, that the crankcase chamber may be considered a pulse chamber associated with the engine and within which fluid pressure pulses are created in response to the reciprocating movement of the piston therein. It is thus generally known that fuel is supplied to the engine through the fuel pump in direct response to engine generated, positive and negative pressure conditions within the crankcase. The check valves in the fuel pump are responsive to the positive and negative pressure changes produced by the pressure pulses from the crankcase to open and close and thus control fuel flow to the engine.
Conventional umbrella-type check valves have a standard style seat consisting of a flat surface with one or more fuel flow ports. This standard seat design, together with the valve, forms a large unsupported volume of space and area underneath the valve. The volume of space allows the valve to flex down flat onto the seat when subjected to pressure. This excessive flexing causes cracking and tearing of the valve material which results in reduced pump life. Additionally, excessive deflection of the valve directly reduces the output of the pump since the pump diaphragm must displace the unproductive volume of space underneath the valve on each stroke of the piston.