Function of the Components
Function of the componentsEDS control unit (N39)
Engine 602.962:
Engine 603.970:
The control unit processes the incoming signals and supplies a milliamp current to the vacuum transducers and to the injection pump idle speed electromagnetic actuator. With two additional wires leading to the test connection for diagnosis (X11/4), the entire system can be tested via impulse readout.
Atmospheric pressure sensor (integrated into the control unit)
The EGR volume is affected via the atmospheric pressure sensor, depending on the altitude and the ambient air pressure. The atmospheric pressure sensor provides the control unit with a decreasing voltage signal with decreasing air pressure (increasing altitude). The control unit adjusts the EGR volume to the ambient air pressure by reducing current to the vacuum transducer.
Test connection for diagnostics (X11/4)
Model 124:
The impulse readout for diagnostics can be read out at the test connection.
Air flow sensor (B2/1) with intake air temperature sensor (B2/1a)
Model 126:
Located in the air channel between the air filter and the turbocharger.
The air flow sensor plate is held closed by a return spring. Depending on the amount of incoming air, the plate opens to a specific angle which is measured by a potentiometer, to produce a voltage signal in proportion to the movement of the plate.
The intake air temperature is detected by the temperature sensor (B2/1a) in the air flow sensor.
Vacuum transducers (Y31/1, Y31/2, Y31/3)
Engine 602.962:
Y31/1 EGR valve vacuum transducer
Y31/2 Intake manifold air pressure control valve vacuum transducer
Y31/3 Wastegate vacuum transducer
Engine 603.970:
Y31/1 EGR valve vacuum transducer
Depending on operating conditions, the vacuum transducers receive a respective current from the control unit. The vacuum transducer then supplies a corresponding vacuum to its actuator.
Starter ring gear speed sensor (L3)
Detects the engine speed from the starter ring gear teeth (144 impulses per revolution) and sends it to the control unit in the form of an alternating voltage.
Air pressure sensor (B5/1), engine 602.962
Installed in the component compartment (right side) on the panel in front of the battery. The pressure sensor detects the pressure (P2) in the intake manifold, converts that to a voltage and sends it to the EDS control unit (see graph on following page).
EGR valve (60)
The EGR valve with the mixture tube (602.962 intake air control housing) is bolted on the right side of the cylinder head. It connects the exhaust manifold via a corrugated tube to the intake crossover pipe. The EGR valve is activated by a controlled vacuum from the vacuum transducer.
A Exhaust to the intake manifold
B Exhaust from the exhaust manifold
a Vacuum connection
b Spring
c Diaphragm
d Valve
Coolant temperature sensor (EDS) (B11/4)
Coolant temperature is detected by the coolant temperature sensor (B11/4).
It is monitored by the EDS control unit. The resistance of the coolant temperature sensor varies, depending on coolant temperature.
Intake manifold air pressure control valve body (94a) with intake manifold air pressure control valve (99) and vacuum actuator (100), engine 602.962
A vacuum-actuated intake manifold air pressure control valve is located in the intake manifold air pressure control valve body to induce a pressure differential between the exhaust and intake manifolds by partially obstructing the air intake during EGR operation. A minimum opening (arrows) is maintained between the intake manifold air pressure control valve and the intake manifold air pressure control valve body. The vacuum actuator (100) is controlled by the intake manifold air pressure control valve vacuum transducer (Y31/2).
60 EGR valve
100 Intake manifold air pressure control valve vacuum actuator