PURPOSE: To synthetically diagnose the EGI apparatus of a car by continuously detecting the connection and disconnection of the valve opening signals and adding-up fuel injection time if the valve opening signal for injection valve is transmitted within a certain time and confirming the proper fuel feeding.

CONSTITUTION: When fuel injection-time measurement is instructed, injection starting position is detected by judging if the collector voltage Vl is at a high potential H or not, and the interruption which is generated at each time interval as the standard in time measurement is permitted, and a counter N for injection time is increased by 1, and the flag in the case when an injection valve 6 is opened is cleared. When the voltage Vl is at H, the flag is set, and when the voltage Vl is not at H, the counter (k) is increased by 1, and when k is less than a set value kl, the higher potential of Vl is detected, and if k is kl or more, the flag is cleared, since injection time is completed. kl is set so that the time in the multiplication of the time for one loop by kl becomes larger than the cycle of the connection and disconnection of the valve opening signal. The injection time can be calculated by multiplying the counter N by the interruption cycle.