Ans. The purpose of the fuel feed pump is to supply the fuel from the fuel tank to the injection pump. Working of fuel feed pump :- A schematic diagram of fuel feed pump. It is spring loaded plunger type fuel feed pump. The plunger is actuated through a push rod by a cam mounted on the cam shaft. At the minimum lift position of the cam spring force on the plunger creates a suction which causes the fuel to flow from the main tank into the pump when the cam is turned to its  maximum lift position, the plunger is lifted upward. At the same time when the inlet valve is closed and the fuel is forced through the outlet valve.