Fuel Rail and Injectors Each injector contains a solenoid operated needle valve which is closed while the solenoid winding is de-energised. 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 oilcan be applied to the 'O' rings to aid installation. No other form of lubrication should be used.