Fuel Pump: Description and Operation

Mechanical Fuel Pump:

The Fuel Pump, located on the engine, pumps fuel from the fuel tank to the carburetor. The Fuel Pump is a mechanical type (spring diaphragm), that is driven directly from the camshaft. As an eccentric on the camshaft raises and lowers the pump lever arm, the diaphragm moves in and out creating a suction that draws fuel from the fuel tank and expels it under pressure to the carburetor float bowl. Excess fuel pressure is returned to the fuel tank via a return line in the top of the fuel pump. Two flap valves, located in the upper part of the fuel pump, allow fuel to enter from the tank and exit to the carburetor. The Fuel Pump outputs fuel at 2.5 - 3.5 psi.