In this thesis, a new type of alternative fuel direct injection injector actuated by a permanent magnet (PM) plunger bi-directional motion actuator has been developed and investigated. The project composes of the development of the novel PM plunger bi-directional motion actuator, with mathematical modeling and physical analysis, including the system nonlinear magnetic characteristics.  The research demonstrated that this new type of PM plunger actuator could implement bi-directional motion when a properly defined bi-directional voltage is applied to the solenoid. The simulation results and experimental results matched well and validated that the mathematical model of the PM plunger bi-directional motion actuator is appropriate, which can be used as an aid for future design purposes. Moreover, the simulation results show that the injector employing the bi-directional motion actuator can significantly improve the injector closing speed and reduce post-injection