Schematic representation of the ignition components of engines with the TCI system
1 - High-voltage wire of the ignition coil
2 - Ignition coil
3 - High-voltage spark plug wire
4 - spark plug
5 - Ignition control unit (Bosch)
6 - Ignition control unit (Siemens/ Telefunken)
7 - Cable
8 - Distributor housing with centrifugal regulator with weights
9 - Vacuum diaphragm
10 - Retaining ring
11 - Pulse sensor
12 - Sensor rotor
13 — Retaining ring
14 — Dustproof cover
15 - Slider
16 - Distributor
17 - Cylindrical pin
18 - Rotor and protrusions of the pulse sensor
19 - Cover clamp
20 - Pulse sensor connector
Pulse sensor (located in the ignition distributor) and the ignition coil needs to be checked if the spark plugs are not sparking. Check the spark plug wires, coil and spark plugs (see Sections Checking and replacing the ignition coil and Checking and replacing ignition sensors (Motronic system)). There are two types of control units: Bosch and Siemens/Telefunken. Both types can be distinguished by electrical connectors. The bottom of the Bosch unit has one large rectangular connector, while the Siemens/Telefunken unit has two round electrical connectors at the front.
Examination
Power supply and grounding of the ignition control unit
1. With the ignition off, disconnect the cable connectors from the ignition control unit. Connect a voltmeter between pins 2 and 4 of the Bosch system connector or between pins 6 and 3 of the Siemens/Telefunken system.
2. Turn on the ignition. Voltage should appear on these contacts. If there is no voltage, then check the wires for breaks (see chapter Onboard electrical system).
3. Using an ohmmeter, check the connection between pin 2 of the connector (Bosch) or pin 6 (Siemens/Telefunken) and car body. There must be a short circuit.
4. Using an ohmmeter, check the connection between pin 4 of the connector (Bosch) or pin 3 (Siemens/Telefunken) and terminal 15 of the ignition coil. There must be a short circuit.
5. If the reading is incorrect, repair the cable.
Pulse encoder signal
1. If voltage is supplied to the ignition control unit, check the transmission from the AC voltage pulse sensor to the control unit.
2. Use a digital voltmeter for the following tests:
- For Bosch systems, connect the positive lead to pin 5 of the connector and the negative lead to pin 6.
- On Siemens/Telefunken systems, connect the positive probe to the () small connector, and the negative probe to the contact (-).
3. Let the assistant turn the engine over with the starter, while checking for the presence of an alternating voltage of 1 to 2 volts. If there is no voltage, check the cable between the pulse sensor (in the ignition distributor) and control block. If the cable is OK, check the resistance of the impulse sensor.
Do not operate the starter for a long time. If necessary, disconnect the cold start injector electrical connector to shut off fuel to the engine.
4. To check the resistance of the pulse generator, proceed as follows:
- In Bosch units, measure the resistance between pins 5 and 6. The reading should be between 1000 and 1200 ohms.
- On Siemens units, measure the resistance between the pins of the smaller connector. The reading should be between 1000 and 1200 ohms.
5. If the readings are incorrect, replace the pulse sensor. If the resistance values for the pulse generator are correct and the voltages of the control units (Supply voltage and signal voltage are incorrect, replace the control unit.
Replacement
Ignition control unit
1. Make sure the ignition is off.
2. Disconnect the electrical connector from the control unit (s).
3. Turn away screws of fastening of the block of control and take it from an impellent compartment.
4. Installation is reverse to removal.
In Bosch control units, a special dielectric paste is installed between the back of the control unit and the heat sink. In the event of their separation (replacement or check) remove the old paste and clean the heat sink with 180 grit sandpaper. Apply Curil K2 paste (Bosch number 81229243). Silicone dielectric compound can be used instead of paste. This treatment is very important to ensure the long life of these expensive ignition components.
Pulse sensor
If your vehicle's radio is equipped with an anti-theft system, make sure you know the correct activation code before disconnecting the battery. Before disconnecting the wire, refer to Section Anti-theft audio system and instrument panel language.
If a message in a different language appears on the instrument panel display after connecting the battery, refer to Section Anti-theft audio system and instrument panel language.
1. Disconnect the negative battery cable.
2. Remove the ignition distributor from the engine (see Section Removal and installation of the distributor of ignition).
3. Using circlip pliers, remove the circlip holding the sensor rotor.
4. Use two flathead screwdrivers on opposite sides to pry out the sensor rotor and carefully remove it upwards.
Insert the screwdrivers as far as possible without bending the sensor rotor. Only work on the strongest central part of the sensor rotor. In case of bending, the sensor rotor must be replaced.
Make sure the roll pin does not fall out when removing the sensor rotor.
5. Remove the mounting screws, vacuum diaphragm and base from the electrical connector of the impulse sensor.
6. Unscrew the two screws of the vacuum corrector and separate it from the distributor by sliding it down and unhooking it from the base pin.
7. Using circlip pliers, remove the circlip holding the pulse transducer and base.
8. Carefully remove the pulse transmitter together with the base.
9. Remove the three screws and separate the base from the pulse sensor.
10. Installation is reverse to removal.
Don't forget to install an insulating ring between the sensor coil and the base. It must be centered before tightening the fastening screws. It will also be necessary to check/adjust the air gap if the sensor rotor has been removed or encounter an incorrect gap situation (see Section Checking and adjusting the air gap (TCI system)).