Engine management system - MEMS (Fuel Injectors): Description and operation

Coil No. 1 is connected to earth via pin 52 of ECM connector C0914 and coil No. 2 is connected to earth via pin 26 of ECM connector C0914. Each coil receives a battery supply from the main relay, via fuse 2 in the engine compartment fusebox.

Coil No. 1 is fitted above cylinder 1 and is attached to the spark plug for cylinder 1 and the HT lead connects to the spark plug for cylinder 4.

Coil No. 2 is fitted above cylinder 3 and is attached to the spark plug for cylinder 3 and the HT lead connects to the spark plug for cylinder 2.

WARNING: The HT voltage of the ignition system is in excess of 50 kV and the LT voltage is in excess of 400 volts. Voltages this high can cause serious injury and may even be fatal. Never touch any ignition components while the engine is running or being cranked.

CAUTION: Never crank or run the engine with the HT leads disconnected from the ignition coils; failure of the ECM and/or the coil will result. Always disable the ignition system by disconnecting the LT connectors from the coil.

Each ignition coil consists of a pair of windings wrapped around a laminated iron core. The primary winding has a resistance of 0.7Ω and the secondary winding has a resistance of 10 kΩ.

Fuel Injectors

The fuel injectors are located directly under the fuel rail and connect to the intake manifold runners. Each injector delivers fuel to the engine in a targeted, atomised spray (onto the intake valve heads) which takes place once per cycle. Each injector opens during the intake stroke of the cylinder it supplies.

An injector consists of a pintle type needle and seat, and a solenoid winding which lifts the needle against a return spring. The injector nozzle delivers the fuel spray to precise areas of the intake ports to maximise the benefits of the swirl and turbulence in the manifold and head ports.

The solenoid winding has a resistance of 13 - 16Ω at 20°C (68°F). The fuel injectors operate at a regulated pressure of 3.5 bar (50 lbf/in²). The regulator is located on the end of the fuel rail and excess fuel is returned to the swirl pot via a return line to the tank.

The injectors receive fuel under pressure from the fuel rail and a 12 volts supply from the main relay. To deliver fuel to the engine, the ECM has to lift the needle off the injector seat by energising the solenoid.

To energise the solenoid the ECM supplies an earth path from connector C0914 to the winding of each injector on the following pins: l Injector No. 1 - pin 25. l Injector No. 2 - pin 51. l Injector No. 3 - pin 14. l Injector No. 4 - pin 40.