A gas fuel injector of an electromagnetic drive type includes a cylindrical main body in which a fuel passage is formed, an opening/closing valve configured to open and close the fuel passage, a solenoid configured to open the opening/closing valve, and a nozzle provided at a distal end portion of the main body. The opening/closing valve includes a valve body configured to reciprocate together with a plunger constituting the solenoid and a valve seat configured to come into contact with and be separated from the valve body. The plunger is fixed to a retainer provided on an upstream side of the opening/closing valve. The retainer is installed between a closing spring configured to bias the plunger in a valve closing direction and an adjustment spring configured to bias the plunger in a valve opening direction.

An inlet valve assembly of a fluid pump comprises an inlet valve member movable between a closed position and an open position. In the closed position the inlet valve member is arranged to block a pump chamber inlet to prevent fluid from entering or exiting a pump chamber of the fluid pump through the pump chamber inlet. In the open position the inlet valve member is arranged to allow fluid to enter or exit the pump chamber through the pump chamber inlet. The inlet valve assembly further comprises a first biasing means configured to bias the inlet valve member in a first direction, d.sub.1, towards the open position, when the inlet valve member is in the closed position; and a second biasing means configured to reduce the speed of the inlet valve member when the inlet valve member is moving in the first direction, d.sub.1, towards the open position.