The ignition system includes the ignition switch, the battery, the distributor, the primary (low-voltage/low-tension or LT) and secondary (high-voltage/high-tension or HT) wiring circuits, the spark plugs and the spark plug leads. Models fitted with a carburettor or L-Jetronic fuel injection are equipped with a Transistorised Coil Ignition (TCI) system. Models fitted with the Motronic fuel injection system have the ignition system incorporated within the Motronic system (Digital Motor Electronics or DME). is running, the ignition timing is continually
changing, based on the various input signals to the ECU. Engine speed is signalled by a speed sensor. Early Motronic systems have
the position reference sensor and the speed sensor mounted on the bellhousing over the flywheel on the left-hand side. Later Motronic
systems have a single sensor (pulse sensor) mounted over the crankshaft pulley. This sensor functions as a speed sensor as well as
a position reference sensor. Refer to Section 12 for checking and renewing the ignition sensors. Note: Some models are equipped
with a TDC sensor mounted on the front of the engine. This sensor is strictly for the BMW service test unit, and it is not part of the
Motronic ignition system
