Abstract: A fuel injection system for an internal combustion engine of a vehicle including a body having a first air channel and a second air channel formed therein, a fuel injection channel formed in the body, a first mixing chamber formed in the body between the fuel injection channel and one of the first and second air channels, a first valve means positioned in the first air channel for limiting a passage of air therethrough relative to movement of an accelerator of the vehicle, a second valve positioned in the fuel injection channel for limiting a passage of fuel relative to a movement of the accelerator, and a third valve positioned in the second air channel for limiting the flow of air/fuel therethrough relative to a movement of accelerator. The first air channel and the second air channel communicate with each other in the body. The first mixing chamber serves to mix fuel from the fuel injection channel with air from the second air channel.