How It Works
The lever of the pump attached to the diaphragm is activated by an eccentric lobe on the shaft which the pump is connected to, this creates a pressure, pulling the fuel from the tank to the upper chamber of the pump, at this stage the outlet valve is closed sealing the pump chamber.
When the chamber is filled the inlet valve is sealed and the outlet valve is opened allowing the fuel to be pumped to the carburetor, this cycle is repetitive while the engine is turned on.
A return system is incorporated into the pump to allow excess fuel to be returned to the fuel tank, this is incorporated in both mechanical and electric pump fuel systems.