condition even when the speed of rotation of the engine is constant therefore according to the present invention an oblique passage is cut on the surface of the plunger of the injection pump 10 so that rotation of the plunger relative to the cylinder thereof can provide adjustments of the fuel injection period and hence the amount of fuel delivered by the injection pump 10 the technique of cutting the passage on the surface of the plunger to control the amount of delivery of fuel is disclosed in the japanese utility model laying open publication no 50 54420 in the present invention a rack and pinion mechanism is employed as a plunger rotating means formed at right hand end of a rack 96 is a pressure chamber 98 which is connected through a line 100 to the first accumulator 18 thereby forming a feed back circuit when the engine 10 is running the pressure in the feed back circuit including the first accumulator 18 is less than the biasing force of the spring 102 and therefore the rack 96 is urged to the right in the drawing so as to allow the fuel injection pump 10 to deliver a maximum amount of fuel however.