PURPOSE: To obtain a good combustion state, in the captioned device equipped with an oil pressure controller decreasing oil pressure and delaying fuel injection timing when an engine is low loaded, by detecting misfiring of the engine and reducing a function of decreasing said oil pressure when the misfiring is detected.

CONSTITUTION: When an engine is low loaded, a governor spring 39, connected with one end 43 to a turning shaft 42 of a control lever 41 interlocking to an accelerator pedal, is provided with small tension, and a governor sleeve 23 is moved upward by fly weights 20, then pressure in a pump chamber 4 is decreased. In accordance with the above, pressure in a pressure oil chamber 52 of a timer 44 is also decreased, and a timer piston 46 is pulled back to a delay side by a spring 49. Here the engine misfires, and a misfire detector 53 detects misfiring to excite a solenoid valve 28, if a relief passage 27 is closed, reduction of pressure in the pump chamber 4 is stopped, and injection timing can be set to an advance side even at a low and medium load.