PURPOSE: To allow the fuel to be fed to an engine even when a controller is disabled and improve the reliability by controlling the control rack position by means of a variable resistor when the controller controlling the control rack positon of a Diesel engine by an electronic control circuit is disabled.

CONSTITUTION: An abnormality detection section 5 is fed with a signal having a period of about 15 msec from a microcomputer, and when this signal is stopped, the condition is judged as abnormal. SW1 and SW2 are operated by the signal of the abnormality detection section 5. When a controller 2 is working normally, these switches are connected to the (a) side, and a control rack is controlled by the controller 2, but when the controller 2 is in an abnormal condition, they are connected to the (b) side, and the control rack 7 is controlled by a curent adjusting variable resistor 7. Accordingly, the reliability is improved.