PURPOSE: To provide a 2-4 cycle switchable engine by switching the fuel injection timing of one engine into 2 cycles or 4 cycles.

CONSTITUTION: A solenoid mechanism 5 provided with a leak valve 54 controlled by an electromagnet 52, is installed in a leak flow passage 51 for fuel compressed by operation of the plunger 32 of an unit injector 34. At the time of two cycles, compressed fuel is injected from an injection hole 44 every rotation of an engine by control of the solenoid mechanism 5. On the other hand, at the time of 4 cycles, the solenoid mechanism 5 is controlled so as to reduce pressure of fuel through the leak flow passage 51 once in two times in rotation of the engine. It is thus possible to stop injection of fuel into a cylinder.