Ignition Coil: Description and Operation

GF15.10-P-2100MIR Ignition Coils, Component Description
ENGINE 272.949 in MODEL 230.454 as of Model Year 09 /Modification Year 08 model refinement package
ENGINE 272.968 in MODEL 230.458 as of Model Year 09 /Modification Year 08 model refinement package
ENGINE 273.965 in MODEL 230.471 as of Model Year 09 /Modification Year 08 model refinement package








Shown on cylinder head on the right and left of engine 272

N3/10 ME-SFI [ME] control unit
T1/1 Cylinder 1 ignition coil
T1/2 Cylinder 2 ignition coil
T1/3 Cylinder 3 ignition coil
T1/4 Cylinder 4 ignition coil
T1/5 Cylinder 5 ignition coil
T1/6 Cylinder 6 ignition coil

Location
Ignition coils (single-spark ignition coils) are inserted in the cylinder head, one at the top center of each cylinder.

Task
The ignition coils provide sufficient ignition energy under all operating conditions for the respective cylinder.





Design

1 Pin 1: supply voltage (12 V) from circuit 87 M1 or M3
2 Pin 2: vehicle ground
3 Pin 3: engine ground
4 Pin 4: actuation (circuit 1)
A 4-pin plug connection.
B Capacitive pick up (for diagnosis)
C High-voltage terminal (with integrated spark plug connector)

The ignition output stages are integrated into the ignition coils.

Function
The ME-SFI [ME] control unit (N3/10) actuates the respective ignition coil at "circuit 1". The ignition output stage reacts at the ground end by closing the primary circuit. The current flow in the primary coil causes a magnetic field to form.

Dwell angle control by the ME-SFI [ME] control unit determines the operating time of the ignition coil primary circuit and thus the magnetic saturation of the ferrous core of the ignition coil.

The primary current flow is interrupted at the moment of ignition timing point. Due to the sudden collapse of the magnetic field in the primary coil, the ignition voltage is induced in the secondary coil (generated).

The diode is fitted to suppress any additional ignition spark when the primary current is switched on.

The ignition voltage is delivered to the spark plug through a diode and a high-voltage connection.

Power is supplied to the ignition coils through "circuit 87 M1 and M3".

Diagnosis
Because of the diode it is not possible to measure the resistance of the secondary coil.
The primary current is measured over the capacitive pick up for diagnosing the ignition coils