The electronic injection pump is the heart of the fuel control system. The rotary distributor pump uses an electromagnetic control valve to regulate fuel flow inside the pump. Four plungers in the pump pressurize fuel for distribution to the injectors. A PCM-controlled electronic stepper motor controls plunger timing via an advance piston.
The PCM uses information regarding engine coolant temperature, engine speed, accelerator position, fuel temperature, the optical sensor, and air conditioning status to calculate when to energize the fuel solenoid driver (figure 5-11). The PCM also illuminates the โService Throttle Soonโ lamp and/or Malfunction Indicator Lamp (MIL) in the instrument panel to alert the driver to conditions requiring service.
The PCM also has the capability to interrupt fuel supply when conditions warrant. It does this by de-energizing the normally closed engine shutoff (ESO) solenoid. When de-energized, the solenoid plunger prevents fuel from entering the charging passages in the pump.
