Ignition System: Description and Operation

Ignition

Ignition
The engine has an inductive ignition system with static ignition voltage distribution. Each cylinder has a separate ignition coil, which is plugged directly into the cylinder head cover.
The ignition coils transform the low-tension voltage in the vehicle's onboard electrical system into the high-tension voltage employed to ignite the air-fuel mixture within the combustion chambers. The firing order is 1-4-2-3. The engine is installed in a transverse layout.

Brief component description
Descriptions of the following ignition components are provided:

Ignition coils
The ignition circuit of this coil ignition consists of:
- Ignition coil with primary and secondary coil
- Ignition output stage in the engine control unit
- Spark plugs, connected to the secondary winding

Each spark plug receives its high-tension voltage from its own ignition coil (pencil coil) and a separate individual ignition output stage within the engine control unit.
The ignition coils receive power from Terminal 30 from the ignition's load-shedding Terminal 15 relay.







The Terminal 15 load-shedding relay is in the engine-compartment power distribution box.







The spark plugs emit high-frequency interference pulses. A means is required to suppress them. The interference-suppression capacitor prevents interference from being propagated through the vehicle's electrical system. The interference-suppression capacitor is connected to earth in the load circuit. Always observe the diagnostic wiring diagrams when servicing this equipment.

System functions
The following system functions are described:

Ignition circuit monitoring
The ignition circuit is monitored on the basis of the current in the primary coil of the ignition coil. When the engine is switched on, the current must stay within specific values during certain time thresholds. The ignition diagnosis monitors the:
- Primary circuit of the ignition coil
- Wiring harness for the ignition
- Secondary circuit of the ignition coil with spark plug
- Spark duration

The following faults can be detected by the ignition circuit monitoring:
- Short circuit at the primary side of the ignition coil
- Short circuit on the secondary side of the ignition coil
- Spark plug
- Line disconnection of the activation
- Faulty ignition output stages

The following cannot be detected:
- Sporadic faults such as loose contacts in the wire to the actuator
- Flashovers in the high voltage circuit parallel to the spark gap without the formation of an interturn fault

Notes for Service department

General notes

NOTICE: Multiple spark ignition only in range close to idle.

Multiple spark ignition occurs only during the warm-up phase (maximum of roughly 65 °C) and in the engine speed range around idle.
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