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 (42, 70) arranged to control a quantity of fuel delivered to the pumping chamber during retracting motion of the pumping plunger, said inlet metering valve (42, 70) including: a metering valve member (66, 90) 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 (66, 90) from said closed position to said open position defining a variable flow area that increases as said metering valve member (66, 90) moves from said closed position toward said open position; an actuator piston (60, 80) in an actuator bore (58, 74) exposed to pressure in said common rail, said actuator piston (60, 80) 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 (60, 80) including a valve stop (64, 86) that determines a metering position of said metering valve member (66, 90); wherein said metering valve member (66, 90) opens during retracting motion of said pumping plunger to a metering position such that the metering valve member (66, 90) opens until contact is made with said valve stop (64, 86), said metering position defining a variable flow area which is a function of the pressure in the common rail communicated to the actuator bore (58, 74). an inlet metering valve (42, 70) arranged to control a quantity of fuel delivered to the pumping chamber during retracting motion of the pumping plunger, said inlet metering valve (42, 70) including: a metering valve member (66, 90) 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 (66, 90) from said closed position to said open position defining a variable flow area that increases as said metering valve member (66, 90) moves from said closed position toward said open position; an actuator piston (60, 80) in an actuator bore (58, 74) exposed to pressure in said common rail, said actuator piston (60, 80) 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 (60, 80) including a valve stop (64, 86) that determines a metering position of said metering valve member (66, 90); a metering valve member (66, 90) 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 (66, 90) from said closed position to said open position defining a variable flow area that increases as said metering valve member (66, 90) moves from said closed position toward said open position; an actuator piston (60, 80) in an actuator bore (58, 74) exposed to pressure in said common rail, said actuator piston (60, 80) 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 (60, 80) including a valve stop (64, 86) that determines a metering position of said metering valve member (66, 90); wherein said metering valve member (66, 90) opens during retracting motion of said pumping plunger to a metering position such that the metering valve member (66, 90) opens until contact is made with said valve stop (64, 86), said metering position defining a variable flow area which is a function of the pressure in the common rail communicated to the actuator bore (58, 74).