Ignition System: Description and Operation

Ignition Component Locations:

The high tension ignition system must be able to deliver sufficient energy to ignite the air/fuel mixture under all conditions. If sufficient ignition energy is not available ignition does not occur and the resultant combustion miss produces reduced power and unacceptable tail pipe emissions. For this reason Mercedes Benz uses a very reliable secondary ignition system consisting of the (2) EZL/AKR control units, (2) ignition coils, (2) high-tension distributor, ignition wires with suppression connectors, and spark plugs. High voltage for cylinders 1, 4, 6 and 7 is routed through the distributor mounted on the left cylinder head, and high voltage for cylinders 5, 8, 3, and 2 are routed through the distributor mounted on the right cylinder head.

The primary side of the coils is connected with the positive battery terminal via the ignition switch. During the primary current-flow time (coil saturation) the coil is connected to ground through the power output transistor of the EZL/AKR control unit (ECU). The ECU receives input signals from the ignition switch, crankshaft position sensor, reference resistor, intake manifold vacuum signal, coolant temperature sensor, throttle valve switch, camshaft position sensor, knock sensors, transmission overload protection sensor, and the CIS-E control unit; processes these signals, and calculates the appropriate dwell/ignition angle, and simultaneously switches the ignition coil ground circuit.