Operation

Operation

Battery voltage is supplied to the main relay and fuel cut-off solenoid relay via fusible link H on G wires. The starter relay is supplied battery voltage via fusible link D, also on a G wire. All 3 relays are contained within the relay module.

When the ignition is switched ON, a voltage is fed to the ECM on a G/K wire, from fuse 24 in the passenger compartment fuse box. The ECM connects an earth to the other side of the main relay coil on the W/K wire, thereby energising it.

Power is fed through the main relay contacts and on N/O wires to the ECM, fuel injection pump, glow plug relay, mass air flow sensor, EGR solenoid and to the A/C relay module (where applicable).

Fuel injection timing The ECM determines the optimum fuel injection timing for the injection pump based on the signals it receives from the following sensors:

1. CKP sensor - Engine speed and crankshaft position
2. Needle lift sensor - Start of injection
3. ECT sensor - Engine temperature
4. MAP sensor - Engine load (Bosch ECM only)
5. IAT sensor (Bosch ECM only)