PURPOSE: To control the injection timing and the injecting amount of the unit injector simply and surely by an electric means by a method wherein the timing of closing a metering port is varied by a pressure-feeding plunger in the unit injector.

CONSTITUTION: The unit injector 1 is equipped wth the sending plunger 3, connected to a follower 2, while the pressure-feeding plunger 3 sends fuel in a fuel reservoir 4 forcibly to drive an injection plunger 5. The injection plunger 5 injects the fuel in a pump chamber 6 into a combustion chamber 9 from the injecting port 8 of a nozzle 7. Teeth 20 are cut around the outer periphery of said sending plunger 3 and a rack 21 is engaged therewith. The rack 21 is driven by a servomotor 22 driven and controlled by a controller 19. According to this method, the rack 21 is driven by the servomotor 22 to pivot the plunger 3 when it is necessary and a timing to close the metering port 24 by the cut part 23 of the plunger 23 may be varied.