To reduce liquid fuel collecting in the pressure pulse chamber of the diaphragm fuel pump of a carburetor.

A fuel pump diaphragm held by the body of the carburetor forms a fuel chamber to receive fuel on its one side, and forms a pressure pulse chamber on the other side. The pressure pulse chamber is in communication with an engine, and receives a pressure pulse to actuate the fuel pump diaphragm. Thereby, the fuel is drawn in the carburetor, and the pressurized fuel is sent to a fuel metering assembly in the downstream. An air passage is provided, its one end is connected to an air source, and the other end is connected to the pressure pulse chamber. Airflow is supplied to the pressure chamber, and liquid fuel in the pressure chamber is scavenged, removed and dissipated, or air is mixed in it, in order to avoid the liquid fuel collecting there.