PURPOSE: To make it possible to stop the operation of an air compressor during a local-cylinder engine operation by introducing a non-operating cylinder compressed air into each compressed-air passageway in an air blast valve device which corresponds to a non-operating cylinder and causing injection of fuel from a nozzle port of an air blast valve device, which corresponds to an operating cylinder, by the non-operating cylinder compressed air.

CONSTITUTION: In an air blast valve device 20 disposed at the inner wall surface of a cylinder head 3, when a solenoid 30 is energized with the result that a needle 23 acts on a valve seat 25 to open a nozzle port 24, the previously supplied fuel which remains in the vicinity of the valve portion 25 is injected, together with a compressed air, into a combustion chamber 4 via the nozzle port 24. On the other hand, when the needle 23 opens the nozzle port 24, a compressed air flows into a nozzle chamber 32 and goes toward the nozzle port 24. When it is desired to start a local-cylinder operation during a low-load engine operation, an operation is so made as to open/close the nozzle port 24 of the air blast valve device 20 which corresponds to a non-operating cylinder to thereby supply the compressed air therewithin into an air blast valve device 20, which corresponds to an operating cylinder, via passageways 35, 58 and via a delivery pipe 56.