A fuel injector for an internal combustion engine

A fuel injector (50) for an internal combustion engine includes a main body (51) including a timing bore, a timing plunger (63) disposed in the timing bore, an electronically-operated solenoid valve assembled to the main body (51), a nozzle (54) having a needle bore (72) and an injection needle (75) disposed in the needle bore (72) which needle (75) is operable under certain conditions to lift so as to initiate fuel injection. Disposed between the main body (51) and the nozzle member (54) is a one-piece adapter (53) which is designed to include an axially-extending metering bore and a needle spring cavity (83). A metering plunger (65) is disposed within the metering bore and a biasing spring (76) is disposed within the needle spring cavity (83). At the base of the needle spring cavity (83) is a button (77) which serves as a direct abutment interface between the top of the needle (75) and the bottom of the biasing spring (76). The thickness of the button (77) controls the preload on the spring (76) and this is the force which must be overcome by fuel pressure present in the needle spring cavity (83) in order to allow the needle (75) to lift so as to create an injection opening between the needle (75) and the tip of the nozzle (54) for the fuel at high pressure to be injected.