A diesel engine coupled to a transmission and having a fuel injector control system which among other things monitors the load on the engine by measuring the transmission line pressure, a higher pressure being indicative of a greater load. When the pressure is below a preset value and the engine is sufficiently warm, the normal injector firing sequence is altered by not actuating injectors at spaced intervals in the firing sequence. As the pressure and therefore the load decreases, the intervals between which injectors are not actuated are decreased so that in a given number of engine rotations there are fewer injector actuations and as a result of corresponding cylinders being idle, less fuel is supplied to the engine at lighter loads.