Figure 2. Diaphragm-Type Fuel Pump

Wheeled Vehicle Fuel and Exhaust Systems
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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.