5.2. General information about ignition and precautionary measure system
The system of ignition includes the ignition switch, the battery, the ignition distributor, primary (low-voltage or LT) and secondary (high-voltage or HT) chains, spark plugs and wires of spark plugs. Models with the carburetor or fuel system of injection of L-Jetronic are equipped with semi-conductor system of ignition (TCI). Models with fuel system of injection of Motronic have the system of ignition incorporated with Motronic system (Digital Electronic System of the engine or DME).
Semi-conductor system of ignition (TCI)
This system has four main components: sensor of impulses, control unit ignition, ignition and spark plug coil. The sensor of impulses develops a signal of the moment of ignition for ignition system. It is equivalent to the kulachkovy breaker in the standard distributor of ignition the sensor of impulses develops a signal of an alternating voltage every time when the ledge of a rotor passes by a sensor ledge. When the control unit ignition (knot with the capacitor category) receives this signal of tension, at the expense of interruption of primary chain he creates the spark category.
Time of the closed condition of a chain (duration of a charge of the coil of ignition) is established in the control unit by ignition at the rate of the most intensive iskroobrazovaniye.
The moment of ignition is regulated mechanically (look the Section Check of functioning and moment adjustment ignitions (TCI system)). The centrifugal regulator consisting from podpruzhinenny rotating грузиков, creates an ignition advancing at increase in turns of the engine. The vacuum regulator changes the ignition moment for compensation of change of load of the engine.
System of ignition of Motronic
This system which is also known as Digital Electronic system of the engine (DME), unites in one central block or ECU (computer) all functions of management by ignition and fuel injection. The moment of ignition is defined on the basis of entrance signals in ECU about load of the engine, engine turns, temperature of a cooler and temperature of inlet air. The unique function of the distributor is to submit high-voltage signals on spark plugs. The distributor is established directly on the block of cylinders. In these systems is absent mechanical devices of an advancing of ignition.
The moment of ignition is established by electronic control and in Motronic systems is not regulated. During engine start the sensor of provision of a cranked shaft (the situation sensor) transmits a signal in ECU and by that the initial point of counting of the moment of ignition is defined. In engine operating time the ignition moment continuously changes according to different entrance signals in ECU. Turns of the engine are measured by the sensor of turns. In early systems Motronic the sensor of situation and the sensor of turns are located on a coupling case over a flywheel on the left side. In late systems Motronic the uniform sensor (the pulse sensor), located over a pulley of a cranked shaft is established. This sensor works at the same time as the sensor of turns and situation.
Concerning check and replacement of sensors of system of ignition address to the Section Check and replacement of sensors ignitions (Motronic system).
Some models are equipped with the VMT sensor located in a forward part of the engine. This sensor belongs to the block of test service of BMW and is not a part of system of ignition of Motronic.
At work with semi-conductor system of ignition it is necessary to observe certain precautionary measures:
- Do not disconnect on the working engine of a wire of the battery.
- Be convinced that the control unit by ignition (system of ignition of TCI) it is always reliably earthed (look the Section Check and replacement of the sensor of impulses and the control block ignitions (TCI system)).
- Do not allow hit on the distributor and high-voltage wires of water.
- If it is required to connect a tachometer to the engine, always attach a positive wire (+) a tachometer to negative contact (-) coils of ignition and never - to the distributor.
- Do not allow connection of contacts of the coil of ignition with the case as the sensor of impulses or the coil can fail.
- Do not leave at the muffled engine ignition included for the period of more than ten minutes, differently the engine will not be got.