E. Components With Operation USA Model Year 1984 California
OPERATION EXHAUST GAS RECIRCULATIONE. Components with operation USA model year 1984 California
Injection pump
The emission control system requires a control rod travel indicator. The indicator is attached to pump housing inside in range of control rod.
Overvoltage protection
Located in fusebox on model 126 and behind glove box on model 123. Serves to protect the electronic control unit. Fuse 10 A is installed at top of overvoltage protection.
When the ignition is switched on, terminal 15 is energized. The relay attracts and the control unit is provided with battery voltage.
Electronic control unit
Attached in legroom at the right behind side panelling.
Control unit is connected to battery voltage after ignition has been switched on.
The following signals are put in:
^ Coolant temperature
^ Engine rpm
^ Control rod travel
^ Barometric pressure
The inside of the control unit is provided with bellows (for altitude corrections).
The input signals are processed and the pressure converter (84) or the switchover valve (81) are pertinently activated.
Pressure converter
The vacuum generated by the vacuum pump of the engine is converted into a load-dependent vacuum signal by the pressure converter. The signal serves for controlling the EGR-valve.
Temperature sensor coolant (NTC)
The coolant temperature is obtained by a temperature sensor (83), which is installed on lefthand side of cylinder head. The resistance of the temperature sensor changes in dependence of the coolant temperature.
Rpm sensor
An inductance indicator which is screwed in on intermediate flange to automatic transmission (arrow).
The indicator comprises a magnetic core and a coil. It will pick up the engine speed for transmission to control unit in the shape of an AC voltage.
Control rod travel indicator
The control rod travel indicator is attached to pump housing at the right at level of control rod.
Layout
The control rod travel indicator comprises an iron core, two coils (measuring and fixed value coil) and two short circuit rings. It is connected to the electronic control unit by means of a 3-pole plug.
Coils (3) and (6) are attached to an iron core (2) fixed in housing. The short circuit ring (5) is connected to control rod (1) and slides this control rod free of contact on lower leg of iron core. The fixed value coil (3) and the short circuit ring (4) are attached to upper leg.
Operation
Together with short circuit ring (4) the fixed value coil (3) provides a constant inductance.
The distance between short circuit ring (5) and measuring coil (6) is changed depending on change of location of control rod (1). The resulting variable inductance is compared with the constant. From these data, the electronic control unit determines the control travel.
Switchover valve (electric)
This valve is activated depending on load condition of engine by way of control unit and provides the vacuum for the circulating air safety valve.
Circulating air safety valve
Integrated on compressor housing of exhaust gas turbocharger. The EGR quantity is increased in partial load range by partial reduction of boost pressure.
When the circulating air safety valve is activated with a vacuum, the valve will open and will let a part of the boost air in front of compressor flow back in a bypass system.