Fuel Injection And Ignition System Synchronization, Basic Function - GF07.10-P-9902A

Engine All (CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 

General 

In order to make sequential ignition and injection possible, injection is synchronized with the ignition system. Following synchronization, the fuel is injected sequentially, i.e. the cylinders are selected in the order of ignition. Synchronization also makes knock control and fuel shutoff selectively by cylinders possible.

For synchronization, the combustion engine control unit reads the following sensor signals:

• Crankshaft Hall sensor (engine speed and crankshaft position)
• Camshaft Hall sensor (intake/exhaust camshaft)

Function requirements 

• Engine management ON (circuit 87M)
• Engine in operation

Courtesy of MERCEDES-BENZ USA

Signal evaluation of combustion engine control unit 

Function 

When the engine is started, the combustion engine control unit reads the signal of the crankshaft Hall sensor. The absolute position of the crankshaft, and therefore the TDC, can be determined by means of an irregularity in the sensor rotor (e.g. large pole field gap). Additional information about the position of the camshaft is necessary for determining the top dead center of the power stroke (ignition TDC) of cylinder 1. To do so, the combustion engine control unit reads the camshaft Hall sensor (intake camshaft).

If the signal from the intake camshaft Hall sensor is not available, the signal from the exhaust camshaft Hall sensor is used for detecting the ignition TDC in cylinder 1 instead. If no signal from a camshaft Hall sensor is available, ignition and injection take place after 360° crank angle.