Contents: System with distributor (e7J engine) 🠛 System without distributor (k7M, F3R…🠛 Precautions 🠛
The ignition system is combined with the fuel injection system and form a single engine management system (for more details, see Chapter Power and exhaust systems). Depending on the model, there are two possible types of ignition system.
System with distributor (e7J engine)
The E7J engine is equipped with a distributor; in addition, the ignition system includes a booster module, one ignition coil, a crankshaft speed/position sensor and a knock sensor.
Depending on the information received from various sensors, the electronic control module calculates the ignition timing/ignition coil supply time optimal for a certain engine speed and load, the ECU switches the booster unit, controlling the primary (low voltage) ignition coil circuit. This results in high voltage in the secondary winding, which is then distributed via the high voltage wires to the corresponding spark plug.
The distributor is fixed to the left end of the camshaft. Note that its position has no effect on the ignition timing, the high voltage current is transmitted from the ignition coil to the spark plug. The ignition timing signal is completely controlled by the electronic control module.
A knock sensor is mounted on the cylinder block, which informs the electronic control module that the engine is starting to "knock". This device is sensitive to a certain vibration frequency, thus detecting the knock pulses of early ignition. The knock sensor sends an electrical signal to the electronic control module, which reduces the ignition timing until the "knock" stops - the ignition timing is then gradually returned to the "normal" value. In this way, the ignition timing is maintained as close as possible to the knock threshold - the most efficient setting for the engine under normal operating conditions.
System without distributor (k7M, F3R and F7R engines)
The K7M, F3R and F7R engines are equipped with a distributorless ignition system, which is controlled by the ECU and consists simply of two high-voltage ignition coils, a crankshaft speed/position sensor and a knock sensor. Each ignition coil serves two cylinders (one supplies spark plugs to cylinders #1 and #4, and the other to cylinders #2 and #3). The ignition coils operate on the "wasted spark" principle, meaning that the spark in the spark plugs jumps twice during each engine cycle, on the compression stroke and on the exhaust stroke. The electronic control module uses signals from various sensors to calculate the required ignition timing and ignition coil energization time. The operation of the knock sensor is described above - please note that on F3R engines it is mounted on the cylinder head.
Precautions
To prevent damage to ignition system components and reduce the risk of injury, the following precautions must be observed.
- a) Before disconnecting the system wiring, turn off the ignition.
- b) Before connecting or disconnecting any diagnostic equipment (for example, a strobe) check that the ignition is off.
- c) Do not short the primary or secondary windings of the ignition coil to ground.
Warning! The voltages generated by the contactless ignition system are significantly higher than those generated by a conventional ignition system. Use extreme caution when working on the system with the ignition on. People with an implanted cardiac pacemaker should not touch ignition circuits, components or diagnostic equipment.