Function of injection system: - ra07216020j10x(0010)

U. Electronic diesel system (EDS) J. Location and function of components Engines 602.96, 603.96/97 Turbo 

U. Electronic diesel system (EDS) 

1. j) Location and function of components 

   EDS control unit (N39) 

   The control unit processes the incoming signals and supplies a current (mA) to the vacuum transducers, switchover valves, as well as to the actuator of the injection pump. The entire signal can be checked with the pulse counter by means of a signal, or the fault memory read via an outlet which runs to the test coupling (X92) or (X11/4).

   Fig 1: Identifying EDS Control Unit - Model 124 Behind Battery In Component Compartment

   Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Model 124 behind the battery in component compartment

Model 126 in right footwell behind side panelling

Model 126.13 (Engine 603.970) Installed on right in interior

Model 140

Engine 603.971

Model 201 behind battery in component compartment

Altitude sensor (B18) 

Model Year 1986/87 

The quantity of recirculated exhaust gas is influenced by the atmospheric pressure sensor as a function of altitude or air pressure. The altitude sensor supplies a voltage signal to the control unit which drops as air pressure drops (increasing altitude).

The control unit matches the quantity of exhaust gas recirculated to the respective air pressure by reducing the vacuum transducer current.

Models 124, 201 in component compartment

Model 126 in right footwell

Altitude sensor (integrated in control unit) as of Model Year 1990 

Basic Equipment Code 62/0 as of 06/91 as of Model Year 1992 

The quantity of recirculated exhaust gas is influenced by the atmospheric pressure sensor as a function of altitude or air pressure. The atmospheric pressure sensor supplies a voltage signal to the control unit which is proportional to air pressure (i. e. low voltage with low air pressure). The control unit matches the quantity of exhaust gas recirculated to the respective air pressure by reducing the vacuum transducer current.

Overvoltage protection (K1 or K1/1) 

The power for the electronic control units is supplied through the overvoltage protection relay.

Models 124, 201 behind battery in component compartment

Battery voltage is supplied constantly to terminal 30. A 10 A fuse is fitted between terminals 30 and 30a. The fault memory is energized through terminal 30a. When the ignition is switched on, the relays are actuated through terminal 15 by an electronic unit. The EDS control unit is thus energized through terminal 87E and other ancillaries through terminal 87.

The overvoltage protection is achieved by means of a 22 volts Zener diode. Voltage peaks in excess of 22 volts occurring upstream of the overvoltage protection are switched directly to ground by the Zener diode.

An overload is prevented by a fuse.

Terminals 87E and 87L are protected separately.

Model 126 in component compartment next to ABS control unit

Base module (N16/1) 

Engine 603.971, Model 140 base version Code 62/0, as of model year 1992 

The base module (N16/1) performs the function of the overvoltage protection relay.

Test coupling (X92) or (X11/4) 

Test coupling (X92) 

Model Year 1986/87 

The diagnostic test signal can be tapped via the test coupling.

Model 124 and 201 in right of component compartment

Model 126

Test coupling (X11/4) 

The pulse readout for the diagnosis of the EDS can be tapped via test coupling, contact 4.

Model 124, 201

Model 126

Test coupling (X11/4) integrated in module box 

Model 140 Model Year 1992 

The pulse readout for diagnosis can be tapped at contact 4 of the 38-pin test coupling.

Model 140

Air flow sensor potentiometer (B2/1) 

Fitted in the air flow between air filter and exhaust gas turbocharger.

Model 140

The intake air deflects the air flow sensor flap against the restoring force of a spring into a defined angular position. The position is measured by means of a potentiometer, and converted into a voltage

The intake air temperature is detected by a temperature sensor (B2/1a) in the air flow sensor.

Air flow sensor

Model 201 without round flange

Resistance trimming plug (R18/1) for idling speed 

Model Year 1986, 1987, 1988 

For setting the idling speed.

Specification: 630 ± 20/min.

Model 124

Model 126

Model 201

Reference resistor (R18/2) for exhaust gas recirculation, Model Year 1986, 1987, 1988 

Model 124 in components compartment

Model 126 at right of car interior next to control unit (N39)

Model 201 in component compartment next to battery

Vacuum transducer (Y31/1, Y31/2, Y31/3) up to Model Year 1991 

Vacuum transducer (Y31/1, Y31/4, Y31/5) as of Model Year 1992 

The vacuum transducers are supplied with a control current as an input signal from the control unit depending on the operating state.

The vacuum transducer then supplies the appropriate vacuum for the actuators. As of model year 1992 the vacuum is transmitted from the vacuum transducers through electrical switchover valves to the ARF valve and to the vacuum unit of the vacuum control flap or charge pressure control.

Engine 602.962 Model Year 1990

Engine 603.96 in Model 124

Engine 603.96/97 in Model 126

Engine 602.96 in Model 201

Engine 602.96 Model 124

Basic Version Code 62/0 as of 06/91 as of Model Year 1992

Engine 602.96 Model 201

Basic Version Code 62/0 as of 06/91 as of Model Year 1992

Engine 603.96 Model 124

Basic Version Code 62/0 as of 06/91 as of Model Year 1992

Engine 603.971 Model 140

Base version Code 62/0 as of model year 1992

ARF electrical switchover valve (Y27), ARF microswitch (S27/3) 

Basic Version Code 62/0 as of 06/91 as of Model Year 1992 

Microswitch, compressor cutoff/ARF (S27/6) 

only Model 140 as of Model Year 1992 

The ARF switchover valve (Y27) is actuated 10° before full load by the ARF microswitch (S27/3) of the accelerator control, or by the compressor cutoff/ARF microswitch (S27/6) of the accelerator control. This closes the ARF valve.

Engine 603.96 Model 124

Engine 603.971 Model 140

Base version Code 62/0 as of model year 1992

Engine 603.971 Model 140 as of Model Year 1992

Electrical switchover valves, charge pressure control (Y27/4) or vacuum control flap (Y27/5), Engine 602.96 Basic Version Code 62/0 as of 06/91 as of Model Year 1992 

The electrical switchover valves are supplied with a control current as an input signal from the control unit depending on the operating state, and with the vacuum from the vacuum transducer. They transmit the vacuum in line with the command of the control unit to the charge pressure control valve vacuum unit or vacuum control flap vacuum unit.

Engine 602.96 Model 201

Engine 602.96 Model 201

Typ 201

Electrical switchover valve, charge pressure cutoff (Y31/6), only Engine 603.971 Model 140 Model Year 1992 

If a fault occurs in the charge pressure control loop, the electrical switchover valve (Y31/6) admits air to the charge pressure control valve.

Consequently, no charge pressure is built up and no turbocharger quantity is released by the injection pump.

Engine speed sensor (L3) 

It detects the engine speed at the starter ring gear (144 pulses/revolution) and passes it to the control unit in the form of an alternating voltage.

Coolant temperature sensor (EDS) (B11/4) 

The coolant temperature is detected by the coolant temperature sensor (EDS) (B11/4).

The sensor is actuated by the EDS control unit. The resistance of the EDS coolant temperature sensor varies as a function of coolant temperature.

Bosch pressure sensor (B5/1) 

The pressure sensor detects the existing pressure (P2) and converts it into a voltage which is used as an input signal by the EDS control unit.

Engine 602.96 up to Model Year 1992

Fitted on right behind firewall in direction of travel

Bosch pressure sensor

Absolute pressure characteristic curve (Pabs in mbar) at 5 V voltage

Nippon Denso pressure sensor (B5/1) Engines 602.96, 603.971 as of Model Year 1992 

The function is the same as for the Bosch pressure sensor.

Nippon Denso pressure sensor

Absolute pressure characteristic curve (Pabs in mbar) at 5 volts voltage

Model 124

On right behind firewall in direction of travel

Model 201,140

On left in front of firewall in direction of travel

Tempomat cruise control, Model Year 1990 

In order not to influence the control of the Tempomat cruise control in the part load range, the charge pressure cutoff is rendered inoperative by the Tempomat cruise control/ charge pressure cutoff relay (K12/1) during use of the cruise control.

Model 124

Model 201

ARF valve 

The ARF valve is bolted to the mixing pipe on the side of the cylinder head. It is connected to the exhaust manifold by means of a corrugated pipe. The ARF valve is operated by means of a controlled vacuum from the vacuum transducer (Y31/1).

Version up to July 1991

For noise reasons, the ARF valve is provided with a smaller air passage (a) and a shaped valve seat (b). The connection fitting for the vacuum connection is designed in a tulip shape.

1. Version up to 06/91
2. Version as of 06/91
   Fig 52: Identifying ARF Valve

   Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Engine 602.961/962, 603.960/963/971 

Cast EGR valve (was steel).

Reason: cost and weight reduction.

Model	Engine	Engine end no. Automatic transmission
124.133/193	603.960	046010
124.333/393	603.963	003995
140.134	603.971	001998
201.128	602.961	011387

Model	Engine	Engine end no. Automatic transmission
124.128/188	602.962	017093
201.128	602.961	011441

Engine 603.960/963/971 

EGR valve vent restrictor modified.

Model	Engine	Engine end no. Automatic transmission
124.133/193	603.960	048091
124.333/393	603.963	004100
140.134	603.971	004832

Mixture housing (94a) with vacuum control flap (99) and vacuum unit (100), Engine 602.96 as of Model Year 1990 as of Model Year 1991 

Basic Version Code 62/0 as of 06/91 as of Model Year 1992 

In order to increase the vacuum in the charge air distribution pipe, a pneumatically operated vacuum control flap is fitted to the mixing housing. The vacuum control flap closes the fresh air port during engine operation with ARF. A minimum opening (arrows) between the vacuum control flap and the mixing housing is retained. As of Model Year 1992 the vacuum unit (100) is actuated by the charge pressure control/ vacuum control flap via the vacuum control flap electrical switchover valve (see function diagram).