PURPOSE: To variably control continuous or split injection during a fuel injection cycle irrespective of an engine speed and load to correct a heat emitting characteristic in a combustion process, so as to reduce emission and noise levels.

CONSTITUTION: A hydraulic fluid in a hydraulic fluid transfer pump 24 is pressurized by a high pressure hydraulic fluid pump 32 to be communicated with each injector 14 via an operating part and a manifold 34. Sensor signals S1-S8 indicating various engine parameters are input to a microprocessor 40 including a logic for determining ideal fuel system actuating parameters, and a required hydraulic fluid pressure signal is calculated based on a present operating condition of an engine to be compared with an actual hydraulic fluid pressure signal to output a required current S9 through prescribed algorithm. A solenoid valve 38 is controlled by the current S9 to regulate inner pressure of the manifold 34, so as to be brought into a fuel injection amount, injection timing and an initial injection rate required respectively. High pressure feedback is not required thereby for a hydraulic control valve of the injector 14 to allow use of a simple opening and closing valve.