An attempt is made to develop solenoid operated injectors for diesel engines, to inject natural gas directly into the combustion chamber at high pressure. These new injectors have the size of conventional diesel injectors with small but powerful solenoids located in the former spring chamber, and the spring is moved to a location closer to the nozzle. To provide fast opening and closing of the nozzle, a multiobjective optimization method is used to select the design variables of the injector. The mathematical model used for optimization is developed with the help of experimental results obtained from the solenoid force measurements at transient conditions. The optimization results did show good dynamic performance of the injector, despite the use of a small size solenoid actuator.