A fuel injector includes a housing (12) having a differential piston (32) surrounded by a coil (28), the differential piston (32) carrying and surrounding an armature (66) carrying a needle valve element (68). The valve seat (70) for the needle valve (68) is carried for movement with the differential piston (32). An air chamber (26) in the injector housing (12) communicates with the intake manifold and a fuel inlet (22) to the fuel injector includes a check valve (56). At the beginning of the combustion chamber intake stroke, the differential piston (32) is moved by a spring (64) toward the combustion chamber, enabling the check valve (56) to open and permitting fuel to enter the injector fuel passages (42, 34, 69, 81, 83, 85). Upon increasing pressure within the combustion chamber on the compression stroke, the differential piston (32) is displaced to pressurize the fuel in the injector. Near the top of the compression stroke, the coil (28) is energized and the needle valve (68) is opened to inject pressurized fuel into the combustion chamber. Upon deenergization of the coil (28) the needle valve (68) closes.