Pressure Control Valve

Fig. 4 Pressure Control Valve:

The pressure-control valve, Fig. 4, is mounted very close to the supply pump and connected with the upper recess by a bore. It is a spring-loaded slider valve with which the pump-housing pressure can be varied according to the quantity of fuel being delivered. If fuel pressure exceeds a preset value, the valve piston opens the return circuit and allows fuel to flow back to the pump's suction side. If fuel pressure is too low, this return circuit remains closed. The valve's opening pressure is determined by adjusting the spring preload.