Ignition system function - GF07.10-P-1005MMC

ENGINES 157.9 in MODEL 216.3, 221.0/1

ENGINES 278.9 in MODEL 216.3, 221.0/1

Function requirements for the ignition system, general points

Circuit 87M ON (engine control ON)

Ignition system, general points

A single-spark ignition coil is plugged directly into each cylinder. For the ignition system, the ME-SFI (N3/10) control unit reads the following sensors and signals:

Front knock sensor (left side of engine) (A29/1)
Rear knock sensor (left side of engine) (A29/2)
Front knock sensor (right side of engine) (A30/1)
Rear knock sensor (right side of engine) (A30/2)
LH and RH intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions
LH and RH intake camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions
Coolant temperature sensor (B11/4)
Intake air temperature sensor (B17)
Pressure sensor downstream of throttle valve actuator (B28/7), engine load
Crankshaft Hall sensor (B70), engine speed and crankshaft position

The requirements of the torque coordination function are also taken into account.

For the following partial functions, ignition angle adjustment in the direction "retarded" or "advanced" takes place:

Idle speed control
Inertia fuel shutoff
Transmission overload protection
Knock sensor system
Torque coordination

Function sequence for ignition system

The ME-SFI [ME] control unit sends the signal for the dwell time of the respective operating point to the ignition coil (T1) over the actuation line (circuit 4). The respective ignition coil interrupts the primary circuit by means of an integral fuse after expiry of the dwell time. The ignition voltage passes from the ignition coil to the spark plug (R4) and causes arcing in the air gap between the center and ground electrodes.

Determination of the ignition angle takes place dependent on a performance map according to the input signals from the ME-SFI [ME] control unit.

Ideal development of the primary and secondary current for a multi-spark ignition

Fig 1: Multi-Spark Ignition Voltage Waveform

Courtesy of MERCEDES-BENZ USA

Cylinder arrangement and ignition firing order

Fig 2: Identifying Cylinder Arrangement And Ignition Firing Order

Courtesy of MERCEDES-BENZ USA

Diagnosis

The ignition angles can be checked only with the Diagnosis Assistance System (DAS).

Electrical function schematic for ignition system	Model 216	PE07.10-P-2705-97CAH
Electrical function schematic for ignition system	Model 221	PE07.10-P-2705-97SAH
Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MMB