4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System174Regulating ValveFigure 7-8The regulating valve regulates the fuel feedingpressure of the feed pump so that the fuel pressurein the pump chamber is maintained within thespecified pressure range.When the injection pump revolutions increase toincrease the fuel feeding pressure of the feed pump,the fuel compresses the regulating valve spring tolift the piston. The fuel is then returned to thesuction side as shown by the arrow in the figure.It is therefore possible to regulate the pumpchamber pressure by changing the set force of theregulating valve spring.Figure 7-9Figure 7-9 shows typical relationships betweenpump revolutions and pump chamber pressure. Thehydraulic timer directly uses the pump chamberpressure for controlling the injection timing.
