A battery-less fuel injection system, provided with an injector for injecting fuel supplied to an engine, a fuel pump for supplying fuel to the injector, and an ECU for controlling the injector, wherein a fuel pressure sensor for detecting the fuel pressure given to the injector is provided, and the ECU controls the fuel injection in the process of starting the engine, so that execution of fuel injection is suspended when the fuel pressure detected by the fuel pressure sensor is a set pressure or less, until it is confirmed that the detected fuel pressure has exceeded the set pressure.