Abstract: a fuel system for mixture-compressing internal combustion engines controls the pressure differential of the extraction air required for proportioning the fuel. The system includes a fuel proportioning device and a vane pump for generating a carrier air stream for transporting the fuel into the suction tube of the internal combustion engine. A control valve constructed as a differential pressure valve influences the air pressure at the fuel outlet area and consequently the differential pressure for fuel proportioning. The throttle point is located in the carrier air channel upstream from the fuel proportioning area. A change in differential pressure adapts the mixture composition for various operating conditions.