Abstract: A fuel injector includes a housing (2) having fuel upstream inlet and downstream discharge end portions. The discharge end portion is adapted to adjustably receive a valve assembly (9). The valve assembly, in turn, includes a valve poppet (18), seat (17) and biasing primary compression spring (21) arrangement which is adjustable prior to the assembly's insertion into the injector housing. The inlet end portion of the housing includes a magnetic coil (25) and an armature (29) which forms a working gap (33) with the housing. The armature is attached to an actuator (34) which engages the valve assembly. A secondary compression spring (37) is confined between the armature and an upstream fuel inlet member (39) adjustably mounted to the housing. A first or preload adjustment is to the compression of the primary spring in the valve assembly, which is then inserted into the housing.