PURPOSE: To control each of a pre-stroke variable mechanism and a phase changing mechanism, which can change freely the rotational phases of an engine and a fuel injection pump, by providing each mechanism and determining optimum injection rate and injection timing by using an arithmetic unit.

CONSTITUTION: Optimum fuel-injection rate and injection timing are affected by the speed of revolution, quantity of injection, temperature of the outside air, temperature of cooling water, etc. of the engine. Accordingly, the speed of revolution N, quantity of injected fuel Q, temperature of the outside air T, temperature of cooling water W, etc. of the engine are detected by sensors of every kind, and the informations are inputted to the arithmetic unit 7. The arithmetic unit 7 arithmetically operates optimum injection rate and injection timing on the basis of these informations of every kind, and the pre-stroke variable mechanism 5 and the phase changing mechanism 6 are controlled by outputs from the unit. The engine is rotated by the optimum injection rate and optimum injection timing by controlling the pre-stroke variable mechanism 5 and the phase changing mechanism 6.