A high pressure fuel pump in which a pumping plunger is driven by a cam follower in contact with a profile of a rotating cam , the pumping plunger reciprocating axially in a pumping chamber between a retracting motion during which fuel is delivered to the pumping chamber and a pumping motion during which the plunger pressurizes fuel in the pumping chamber , said pressurized fuel flowing through a pump outlet passage to a pressurized common rail , said fuel pump comprising: an inlet metering valve arranged to control a quantity of fuel delivered to the pumping chamber during retracting motion of the pumping plunger , said inlet metering valve including: a metering valve member movable between a closed position preventing fuel flow into the pumping chamber and an open position allowing fuel to fill the pumping chamber , movement of said metering valve member from said closed position to said open position defining a variable flow area that increases as said metering valve member moves from said closed position toward said open position; an actuator piston in an actuator bore exposed to pressure in said common rail , said actuator piston biased toward a first position corresponding to low pressure in said common rail and movable toward a second position corresponding to maximum pressure in said common rail , said actuator piston including a valve stop that determines a metering position of said metering valve member ; wherein said metering valve member opens during retracting motion of said pumping plunger to a metering position such that the metering valve member opens until contact is made with said valve stop , said metering position defining a variable flow area which is a function of the pressure in the common rail communicated to the actuator bore . an inlet metering valve arranged to control a quantity of fuel delivered to the pumping chamber during retracting motion of the pumping plunger , said inlet metering valve including: a metering valve member movable between a closed position preventing fuel flow into the pumping chamber and an open position allowing fuel to fill the pumping chamber , movement of said metering valve member from said closed position to said open position defining a variable flow area that increases as said metering valve member moves from said closed position toward said open position; an actuator piston in an actuator bore exposed to pressure in said common rail , said actuator piston biased toward a first position corresponding to low pressure in said common rail and movable toward a second position corresponding to maximum pressure in said common rail , said actuator piston including a valve stop that determines a metering position of said metering valve member ; a metering valve member movable between a closed position preventing fuel flow into the pumping chamber and an open position allowing fuel to fill the pumping chamber , movement of said metering valve member from said closed position to said open position defining a variable flow area that increases as said metering valve member moves from said closed position toward said open position; an actuator piston in an actuator bore exposed to pressure in said common rail , said actuator piston biased toward a first position corresponding to low pressure in said common rail and movable toward a second position corresponding to maximum pressure in said common rail , said actuator piston including a valve stop that determines a metering position of said metering valve member ; wherein said metering valve member opens during retracting motion of said pumping plunger to a metering position such that the metering valve member opens until contact is made with said valve stop , said metering position defining a variable flow area which is a function of the pressure in the common rail communicated to the actuator bore . <EOS>