It consists of following major parts:
(i) Rocker arm, return spring and connecting link.
(ii) Sediment bowl with retainer.
(iii) Lower body contains diaphragm, link and spring.
ivi) Upper body contain inlet and outlet check valves.
While camshaft turns, rocker arm of fuel pump is motivated back and forth. The unusual on camshaft pushes the rocker arm lacerate towards body of fuel pump. As the eccentric move off, go back spring pushes rocker arm forward towards engine camshaft. As the rocker arm is pressed back through the eccentric diaphragm in pump is pulled down, which make suction in the major chamber. During this point, inlet valve opens due to suction cause and fuel rush into the major chamber as of the inlet chamber. When eccentric pressure on rocker arm is out, the diaphragm moves upwards due to tension of the spring placed under it. At this time the outlet valve opens with the fuel is pump out of fuel pump. Working of Mechanical Fuel Pump As eccentric pushes rocker arm:
(i) Diaphragm is pulled down during the connecting link.
(ii) Suction or vacuum is formed in the major chamber.
(iii) Inlet valve opens.
(iv) Fuel rushes into the major chamber.
(v) Outlet valve remains closed.
Due to the up and clown movement of diaphragm suction and pumping cause is repeat again and again. Fuel as of the tank is drawn and pumped to carburettor with this action of pump.