PURPOSE: To prevent stoppage of Diesel engine by forming a simulated accelerator opening signal in accordance to whether brake pedal has been stepped or the speed change position is in travel range upon fault of accelerator sensor and idle switch.

CONSTITUTION: Pressure fuel feed through injection pump in Diesel engine will start upon rightward motion of pump plunger 28 and stop upon further rightward motion of plunger pump 28 to open a plunger spill boat 32 from the right end face of spill ring 34 into the pump chamber. The position of spill ring 34 is controlled by a control circuit 16 receiving detected levels from accelerator sensor 42 and idle switch 46 through a spill actuator 36. Upon fault of accelerator sensor 42 and idle switch 46, the control circuit 16 will form a simulated accelerator opening signals in accordance to on-off of brake switch 48 and neutral switch 52 to backup to assure operation.