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

ENGINE 157.9 in MODEL 212, 218

ENGINE 278.9 in MODEL 207, 212, 218

Function requirements for the ignition system, general points

Circuit 87M ON (engine timing ON)

Ignition system, general points

Each cylinder is equipped with a directly inserted ignition coil (T1). The ME-SFI [ME control unit (N310) reads in the following sensors and signals for the ignition system:

Left cylinder bank front knock sensor (A29/1)
Left cylinder bank rear knock sensor (A29/2)
Right cylinder bank front knock sensor (A30/1)
Right cylinder bank rear knock sensor (A30/2)
Left and right intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions
Left and right exhaust camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions
Coolant temperature sensor (B11/4) (model 207, 212), coolant temperature sensor (B11/4) (model 218)
Charge air temperature sensor (B17/8)
Pressure sensor downstream of throttle valve (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
Deceleration fuel shutoff
Transmission overload protection
Knock control
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 over the actuation line (circuit 4). The respective ignition coil interrupts the primary circuit by means of an integral fuse after expiration 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 characteristics map according to the input signals from the ME-SFI [ME] control unit.

In the classic operating mode the ignition coil is charged once per ignition process and generates an ignition spark. For new combustion systems the requests on the ignition also increase. For supercharged engines the ignition coil must provide a high secondary voltage so that an ignition spark can be generated.

Diagnosis

The ignition angles can be checked using the Xentry diagnostics.

Engine configuration and ignition firing order

Fig 1: Identifying Engine Configuration And Ignition Firing Order

Courtesy of MERCEDES-BENZ USA

Electrical function schematic for ignition system	MODEL 207	PE07.10-P-2705-97EAI
	MODEL 212	PE07.10-P-2705-97DAK
	Model 218	PE07.10-P-2705-97XAC
Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MM