Fuel rail

Fuel rail, injectors and fuel pressure regulator from a four cylinder engine.

A fuel rail, for direct injection engines known as a common rail, is essentially a pipe (usually resembling a rail) used to deliver fuel to individual fuel injectors on internal combustion engines. It is designed to have a pocket or seat for each injector as well as an inlet for a fuel supply. Some fuel rails also incorporate an attached fuel pressure regulator. Fuel rails are used on engines with multi-point fuel injection systems, although some multi-point systems use a fuel distributor with individual pipes or tubes to feed each injector.