In general, the subject matter described in this disclosure can be embodied in a fuel injector that includes an upper housing portion that defines an inlet passage adapted to receive fuel, and a lower housing portion that is attached to the upper housing portion and that defines an injector outlet adapted to dispense fuel. The fuel injector includes an electromagnetic coil assembly that is user removable while the upper housing portion remains attached to the lower housing portion. The fuel injector includes a movable pintle that is biased to a closed position that is adapted to prevent fuel from flowing through the injector outlet, and movable, responsive to magnetic force produced by energizing the electromagnetic coil assembly, to an open position that is adapted to permit fuel to flow through the injector outlet.

In general, the subject matter described in this disclosure can be embodied in a fuel injector that includes an upper housing portion that defines an inlet passage adapted to receive fuel; a lower housing portion that defines a pintle-receiving cavity and an injector outlet; an electromagnetic coil assembly; a movable pintle that is: (i) located in the pintle-receiving cavity, (ii) biased to a closed position that is adapted to prevent fuel from flowing through the injector outlet, and (iii) movable, responsive to magnetic force produced by energizing the electromagnetic coil assembly, to an open position that is adapted to permit fuel to flow through the injector outlet; and a guide that is: (i) adapted to guide the movable pintle within the pintle-receiving cavity, and (ii) sized to be spaced apart from the movable pintle and provide a fluid bearing for the movable pintle during pintle movement.

A method for hard machining at least one orifice into a heat-treated fuel system component can include mounting the component into a holding fixture. The at least one orifice can include a first orifice. The method can include determining a desired orifice size of the at least one orifice based on a desired flow rate. The method can include hard machining the first orifice into the component. The method can include forming a first portion of the first orifice. The method can include forming, at an end of the first portion, a second portion of the first orifice. A diameter of the second portion can be smaller than a diameter of the first portion. The method can include forming a corner between the first portion and the second portion. The corner can have an edge condition having a dimension of 50 microns or less.