Abstract: A fuel injection system for an internal combustion engine includes an air suction pipe, a throttle valve located in the pipe, and a member, upstream of the throttle valve, which is actuatable by air flowing through the suction pipe so as to move a piston valve to dose a quantity of fuel to a fuel injection nozzle. The system includes a duct which bypasses the throttle valve, the duct having a valve which closes the duct when the throttle valve is closed and when the engine is above the idling speed. Dosing of fuel is thereby stopped during coasting of a vehicle, leading to decreased fuel consumption.