The invention is directed to a fuel injection apparatus for two-stroke engines and is especially for small engines of high-speed tools such as motor-driven chain saws, for example. It provides for the valve-controlled input of fuel into a pressure chamber of a housing and includes a spring-loaded pump piston journalled for reciprocatory movement in a bore to supply the fuel. The pump piston is sealed by an annular seal. For fuel induction, the pump piston has a passageway opening into the pressure chamber and a valve seat. The valve seat of the pump piston cooperates with a substantially free-flying sealing body for opening and closing the valve.