The fuel rail is bolted rigidly to the engine and it provides the upper mount for the fuel injectors. It distributes fuel to the individual injectors. Fuel is delivered to the input end of the fuel rail by the fuel lines, goes through the rail, then to the fuel pressure regulator. The regulator keeps the fuel pressure to the injectors at a constant pressure. The remaining fuel is then returned to the fuel tank. The fuel rail also contains a spring loaded pressure tap for testing the fuel system or relieving the fuel system pressure.