The general operating principal of the pump may be easily understood by following the fuel circuit through the pump.
FUEL FLOW
First, the fuel is drawn into the pump inlet, and through the inlet filter screen by the transfer pump. Excess fuel is bypassed through the pressure regulator assembly, and back through the suction side. The fuel, which is under transfer pump pressure, flows through the rotor and head. (Figure 4-33).
From here, the fuel is routed in a number of different directions. Some of the fuel is sent through the head locating screw to the automatic advance. The majority of the fuel is sent into a connecting annulus to the top of the hydraulic head. (Figure 4-34).
From this point fuel is sent to the transfer pump test tap and the vent wire assembly. The remaining fuel is sent through a connecting passage to the metering valve. (Figure 4-35).
METERING VALVE
The metering valve, which is controlled by the governor, regulates fuel flow into the head charging ports. (Figure 4-36). It is the equivalent of a throttle plate in a carburetor. It controls the flow area to the pumping plungers. Figure 4-37 shows minimum flow area, and Figure 4-38 shows maximum flow area.
Figure 4-39 shows the vertical straight edge and hole type metering valves. The 6.2L uses the vertical straight edge type.
