Model application/Type
| BX 19 GTi 16v (pre 1991) | Motronic ML4.1 |
| BX 19 GTi 16v (from 1991) | Motronic M1.3 |
| HT leads | Champion LS-10 |
| Spark plugs Type Electrode gap | Champion RC7YCC 1.6 mm NGK BCP7ET |
Torque wrench settings Nm lbf ft
Spark plugs:
| Taper seat type | 12 9 |
| Flat seat type (with washer) | 25 18 |
General information
The electronic control unit (ECU) incorporated in the system is triggered by the ignition circuit and sends impulses to the injectors, which operate simultaneously and inject fuel in the vicinity of the inlet valves. The ECU is provided with sensors to determine engine temperature, speed and load, and the quantity of air entering the engine.
Two types of Motronic engine management systems have been fitted to the Citroën BX 16valve their model applications being as follows:
- BX 19 GTi 16v (pre 1991) Motronic ML4.1
- BX 19 GTi 16v (from 1991) Motronic M1.3
Operation of these system types is fully explained in the Fuel Injection page the main components of the ignition function of each system type being as follows:
The following sensors supply the ECU with information:
- Electronic control unit (ECU) – located under the driver’s seat, the ECU controls the system components and receives signals from various sensors.
- Ignition coil – for the Motronic ML4.1 and M1.3 systems, a conventional ignition coil is used, being triggered by signals from the ECU.
- HT distributor – the distributor simply distributes HT current to the spark plugs and consists of a rotor arm on the end of the inlet camshaft and a conventional distributor cap.
The following sensors supply the ECU with information:
- Air temperature sensor – measures the temperature of the air entering the engine (integral with the airflow meter)
- Throttle position switch – senses the position of the throttle valve
- Coolant temperature sensor
- Knock sensor (only fitted to BX 19 GTi 16v with Motronic M1.3) – senses the engine vibrations associated with pre-ignition, which may cause engine damage unless the ignition timing is retarded as a preventative measure.
- Lambda (oxygen) sensor (only fitted to models equipped with Motronic M1.3 and catalytic converter) – measures the oxygen content of the exhaust gases.
- TDC sensor – measures engine speed and crankshaft position
Ignition Layout From Citroen Manual
Ignition layout from citroen manual
Ignition layout from citroen manual
