Lesson 1/Learning Event 1
FIGURE 2. DIAPHRAGM-TYPE FUEL PUMP.
When the camshaft eccentric rotates 180, it no longer pushes the rocker arm down. The rocker arm spring
then forces the rocker arm to pivot on its pin in the opposite direction. The compressed diaphragm spring
now pushes upward, putting pressure on the fuel in the pumping chamber. The pressure created by the
diaphragm spring closes the inlet valve and forces fuel through the outlet valve to the carburetor bowl. The
diaphragm moves up and down in this manner until the carburetor bowl is filled with fuel.