Electronic fuel injection system for engine

An electronic fuel injection system for an engine comprising a self-triggered ignition unit for generating ignition signals induced on the primary side of an ignition coil in synchronism to the rotation of an engine crankshaft, said ignition signals contributing to the ignition, and also generating paired voltage signals before and after and of the opposite polarity to each of said ignition signals, a fuel injection valve for supplying fuel into an intake manifold, and a microcomputer for controlling the "open" time of said fuel injection valve according to an engine operating condition, said system further comprising:

• means for detecting the time interval between adjacent two of said voltage signals for every voltage signal generation;
• judging means for comparing two latest successive time intervals which have been detected;
• and
• means for determining one of said paired voltage signals to be a specific signal for obtaining a fuel injection timing according to the result of judgment by said judging means.