FUEL DELIVERY SYSTEM – Td6, DESCRIPTION AND OPERATION, Description. Each injector is supplied with pressurised fuel from the fuel rail and delivers finely atomised fuel directly into the combustion chambers. Each injector is individually controlled by the ECM which operates each injector in the firing order and controls the injector opening period via PWM signals. Each injector receives a V supply via the main relay. The ECM controls the ground for each injector solenoid and, using programmed injection/timing maps and sensor signals, determines the precise pilot and main injector timing for each cylinder. If battery voltage falls to between 6 and V, fuel injector operation is restricted, affecting emissions, engine speed range and idle speed. In the event of a failure of a fuel injector, the following symptoms maybe observed: l Engine misfire l Idle irregular l Reduced engine performance l Reduced fuel economy l Difficult starting l Increased smoke emissions. The ECM monitors the wires for each injector for short circuit and open circuit, each injector solenoid coil and the transient current within the ECM. If a defect is found, an error is registered in the ECM for the injector in question.
ENGINE MANAGEMENT SYSTEM – TD6 DESCRIPTION AND OPERATION The voltage in the injector output stages is monitored. If a fault occurs it is registered in the memory as capacitor voltage 1 for cylinders 1, 2, 3 and capacitor voltage 2 for cylinders 4, 5, and 6. If a fault occurs of the type 'current on high side too high' or 'current on low side too high, it is assigned to a particular injector. The cause of this fault can be in any of the wires to the three cylinders in that bank because the wires for each bank are bundled. If a fault occurs of the type 'current on high side too high' or 'current on low side too high, the ECM will stop the engine. If the fault is of the type 'load drop, signifying a break in the wiring, the ECM will maintain the engine running providing not more than one injector is affected. Any fault in the injector output stages will result in the ECM stopping the engine. When an injector is installed in the cylinder head, care must betaken to ensure that the mounting claw is in the correct position, the flat side of the claw must face upwards. If the claw is installed incorrectly, the injector will be wrongly installed resulting in the seal at the base of the injector being ineffective and the injector will be loose in the cylinder head. Injector Calibration – To compensate for tolerances in the fuel injection system, a characteristic map with engine specific compensation values is programmed into the ECM on production. If one or more injectors is replaced, the calibration function must be performed to reset the compensation values to 0. This must only be performed when injectors are removed and replaced with new items. The calibration procedure must only be used for this purpose. The procedure is performed using TestBook/T4 and following the onscreen instructions.