Abstract: A fuel injection system wherein a microcomputer carries out an operation of a fuel injection period using a generator mounted on an internal combustion engine as a power supply is provided, which is capable of preventing excessive feeding of fuel to the engine during restarting of the engine to ensure smooth restarting of the engine. The fuel injection system includes a charge storing circuit for carrying out charging of a charge storage element during initial starting of the engine, a discharge circuit for permitting discharge of the charge storage element to be carried out over a long period of time, and a signal generating circuit for generating an initial starting signal when the amount of charges in the charge storage element is below a predetermined level and a restarting signal when the amount reaches the predetermined level or more.