Table of contents: Carburettor models 🠇 Early 1124 cc and 1360 cc…🠇 All other fuel-injected (8-valve)…🠇 1587 cc (16-vaive) models 🠇
Carburettor models
On all carburettor models, a breakerless electronic ignition system is used. The system comprises solely of the HT ignition coil and the distributor, both of which are mounted on the left-hand end of the cylinder head, the distributor being driven off the end of the camshaft.
The distributor contains a reluctor mounted onto its shaft and a magnet and stator fixed to its body. The ignition amplifier unit is also mounted onto the side of the distributor body. The system operates as follows.
When the ignition is switched on but the engine is stationary, the transistors in the amplifier unit prevent current flowing through the ignition system primary (LT) circuit.
As the crankshaft rotates, the reluctor moves through the magnetic field created by the stator. When the reluctor teeth are in alignment with the stator projections, a small AC voltage is created. The amplifier unit uses this voltage to switch the transistors in the unit and completes the ignition system primary (LT) circuit.
As the reluctor teeth move out of alignment with the stator projections the AC voltage changes and the transistors in the amplifier unit are switched again to interrupt the primary (LT) circuit. This causes a high voltage to be induced in the coil secondary (HT) windings which then travels down the HT lead to the distributor and onto the relevant spark plug.
A TDC sensor is fitted to the rear of the flywheel, but the sensor is not part of the ignition system. It is there to be used for diagnostic purposes only.
Early 1124 cc and 1360 cc fuel-injected models
On early (pre-July 1992) 1124 cc models and 1360 cc (KDY engine) fuel-injected models with the Bosch Monopoint A2.2 fuel injection system (see Chapter 4B), a breakerless electronic ignition system is fitted. This operates in the same way as that described above for the carburettor models above.
In addition to system components described above, the system is equipped with an ignition timing retard system. This reduces the nitrous oxide (NOx) content of the exhaust gases. This is achieved by reducing the temperature at the end of the combustion, by reducing the ignition advance at certain engine temperatures. This system is controlled by the fuel injection ECU. The ECU has control over an electrically-operated solenoid valve, mounted in the engine compartment, which is fitted in the vacuum pipe linking the distributor vacuum diaphragm unit to the inlet manifold. At certain engine temperatures, the ECU switches off the solenoid valve, which then cuts off the vacuum supply to the distributor vacuum diaphragm, thereby reducing the ignition advance.
A TDC sensor Is fitted to the rear of the flywheel, but the sensor is not part of the ignition system. It is there to be used for diagnostic purposes only.
All other fuel-injected (8-valve) models
On all other (8-valve) models, the ignition system is integrated with the fuel injection system, to form a combined engine management system under the control of one ECU (see the relevant Part of Chapter 4 for further information).
The ignition side of the system is of the static (distributorless) type, consisting only of two twin-output ignition coils. On early models, the ignition coils are housed in a single unit, mounted on the left hand end of the cylinder head; four HT leads connect the coil output terminals to the spark plugs. On later models, the ignition coils are housed in a single unit, which is mounted directly above the spark plugs - no HT leads are fitted.
Each ignition coil serves two cylinders each (one coil supplies cylinders 1 and 4, and the other cylinders 2 and 3).
Under the control of the ECU, the ignition coil operates on the "wasted spark" principle. The spark plugs are fired in two pairs, twice for each complete cycle of the engine. One plug of each pair will fire on a compression stroke and one on an exhaust stroke; the spark on the exhaust stroke has no effect on the running of the engine and is therefore "wasted". The ECU uses inputs from various sensors to calculate the required ignition advance setting and coil charging time.
On certain models, a knock sensor is incorporated into the ignition system. The sensor is mounted on the cylinder block and prevents the engine "pinking" under load. The sensor is sensitive to vibration and detects the knocking which occurs when the engine starts to "pink" (pre-ignite). The knock sensor sends an electrical signal to the ECU, which in turn retards the ignition advance setting until the "pinking" ceases.
1587 cc (16-vaive) models
On 16-valve models, the ignition side of the system is also of the static (distributorless) type and consists primarily of four ignition coils located in an ignition coil unit fitted to the centre of the cylinder head cover. The coils are integral with the spark plug caps and are pushed directly onto the spark plugs, one for each plug. This removes the need for any HT leads connecting the coils to the plugs. The ECU uses the inputs from the various sensors to calculate the required ignition advance setting and calculate the coil charging time.