System Testing
Checking ignition timingAt idle speed 775 ± 25 rpm
10° BTDC ±2°
To display a secondary image at the oscilloscope, the engine tester must be switched to 4 cylinders, since the car's ignition system is divided into 2 separate ignition circuits. Firing order: 1-3-7-2-6-5-4-8
Ignition circuit I:
High-tension distributor on exhaust camshaft for cylinders 1-4:
1-7-6-4
Ignition circuit II:
High-tension distributor on exhaust camshaft for cylinders 5-8:
5-8-3-2
The high-tension power supply for ignition circuit I comes from the coil installed at the front right, the high-tension power supply for ignition circuit II comes from the coil installed at the front left.
a) Connecting the engine tester
Connect and adjust the engine tester in accordance with the manufacturer's instructions (note that the 4-cylinder measuring range must be selected).
To display the ignition pattern for ignition circuit I (right side), connect the tester to the ignition lead for cylinder 1 and the front right coil.
To display the ignition pattern for ignition circuit II (left side), connect the tester to the ignition lead for cylinder 5 and the front left coil.
NOTE: If a fault is indicated for all cylinders, it must be in the primary or secondary current circuit from the coil to the distributor rotor. If the fault is indicated for one cylinder only, it must be located after the distributor rotor.
b) Resistances at coil, high-tension distributor and spark plug caps
Coil (Ohms/V):
Primary resistance
Terminals 1 + 15 - 0.4 - 0.7 Ohms
Secondary resistance
Terminals 1 + 4 - 5.0 - 8.7 KOhms
Voltage at
terminal 15 with engine running > 10 V
High-tension distributor (Ohms):
Distributor rotor
Suppression resistor 1 KOhm
- Inspect for damage, tracking or oxidation.
Spark plug caps (Ohms)
Suppression resistor 3 KOhms
- Inspect for damage, tracking or oxidation.
C) Activating the high-tension side
To speed up troubleshooting in the ignition system, the ignition trigger signal can be simulated. To do this, disconnect the 2-pin connector (arrow) above the ZEL (green/white lead). Connect plug pins with test leads.
- Connect oscilloscope tester lead terminal 4 to ignition lead terminal 4.
- Switch on the ignition. If 12 V is applied at intervals to one of the two plug pins with the test lead, a high-tension peak should be visible each time on the oscilloscope screen (ignition trigger).
- If no signal is visible, check:
- Power supply to output stage and coil.
- Ground point for output stages (under right-hand coil).
- Plug connections at output stages, coils and high-tension distributor.
- The high-tension components (e.g. coil, ignition leads, spark plug caps ...)
- Wiring continuity from control unit plug to output stage (green lead: ignition lead I, white lead: ignition lead II).
d) Check output stage control signal
- Check at both (disconnected) output stage plugs.
- Connect the positive tester lead to terminal 5 and the negative tester lead to terminal 2 of the disconnected output stage plug. Crank the engine with the starter motor. The oscilloscope must display a control signal for each output stage plug.