PURPOSE: To reliably check operation of a safety mechanism at the starting of an engine without the need for dry special operation, by installing a checking mechanism which allows operation of the safety mechanism only when the detected value of a coolant pressure sensor exceeds a specified value.

CONSTITUTION: A safety mechanism 21 consists of a hydraulic switch SW5 which turns ON when lubricating oil pressure becomes below a given value, a normally-opened contact R6-a of a sixth relay R6, and a third relay R3 for operating a fourth relay R4, and the fourth relay controls a fuel electromagnetic valve V2 through a fifth relay R5. A check mechanism 22 consists of the sixth relay R6 which allows excitation of the third relay R3 resulting from turn-ON of the hydraulic switch SW5 through turn-ON of the normally-opened contact R6-a by effecting excitation with a pressure sensor S2ON. This allows operation of the safety mechanism only when an engine is brought into a steady operating condition.