18 SENR9977 Systems Operation Section The cam plate moves the distributor plunger toward the head of the distributor (26). The high pressure is created by a decrease in the volume between the distributor plunger and the head of the distributor. The cam plate is pressed to the ring by two springs (28). This brings the distributor plunger back to the original position. The fuel solenoid valve closes the high pressure volume. Distribution and Injection g01132170 Illustration 18 Delivery valve in the closed position The delivery valve ensures that the pressure waves do not allow a reopening of the injector . The pressure waves are created at the end of the injection process.
The valve cone is lifted by the fuel pressure. The fuel is forced through the fuel line to the injector. The delivery ends and the fuel pressure drops. The valve spring presses the valve cone onto the valve seat. The reopening of a fuel injector has a negative effect on emissions. g01132136 Illustration 16 The rear view of the Bosch VP30 fuel injection pump (29) Fuel solenoid valve (30) Delivery valve (31) Timing solenoid valve Timing The distribution of fuel to the injectors takes place through the rotating movement of the distributor plunger. The fuel solenoid valve meters the amount of fuel by the following operations:
Retarding of the fuel injection is the direct relationship between the start of injection and the position of the piston. The timing compensates for the higher RPM of the engine by advancing the start of injection. Time of closure Duration time Start of injection Amount of fuel g01132164 Illustration 17 Delivery of fuel from the open delivery valve