Fuel Injectors

Fuel Injectors

An electromagnetic, top feed fuel injector is installed in each cylinder inlet tract of the inlet manifolds. A common fuel rail supplies the injectors with fuel from a returnless fuel delivery system. the fuel in the fuel rail is maintained at a pressure of 3.5 bar by a pressure regulator incorporated into the pump unit in the fuel tank. A Schraeder valve is installed in the fuel rail, to the rear of injector No.7, to enable the fuel pressure to be checked.







Each injector contains a solenoid operated needle valve which is closed while the solenoid winding is de-energized. the solenoid winding is connected to a power feed from the main relay and to an earth through the ECM. the ECM switches the earth to control the opening and closing of the needle valve (injector 'firing'). While the needle valve is open fuel is sprayed into the cylinder inlet tract onto the back of the inlet valves. the ECM meters the amount of fuel injected by adjusting the time that the needle valve is open (injector pulse width).

Each injector is sealed with two 'O' rings which should be renewed whenever an injector is refitted to an engine. A small amount of engine oil can be applied to the 'O' rings to aid installation. No other form of lubrication should be used.







Measuring the electrical resistance of the solenoid winding enables an assessment to be made of the serviceability of an injector. Nominal resistance of the solenoid winding is 14.5 ± 0.7 ohms at 20°C

the ECM can detect electrical inconsistencies within each injector. It can also detect, via feedback from the HO2S, mechanical faults such as blockage or leakage. the ECM will store a relevant fault code in these circumstances. the ECM will also store the engine speed, engine load and details of either the battery voltage, engine coolant temperature or intake air temperature. the precise details stored depend on the exact nature of the fault detected.

T4 will also display data regarding injector operation via its live readings. Care must be taken when analyzing this data, as the precise timings will vary considerably. Individual timings will be affected by any current engine load.