Fuel Rail
A metal or plastic pipe that delivers pressurized fuel from the fuel lines to the individual fuel injectors on the engine.
A fuel rail is a manifold pipe mounted on top of the engine intake manifold. Its primary job is to distribute highly pressurized fuel from the fuel supply line evenly to each of the engine's fuel injectors. The fuel injectors are mounted directly into ports along the fuel rail.
In gasoline direct injection (GDI) and diesel engines, the fuel rail must withstand incredibly high pressures (ranging from 2,000 to over 30,000 PSI). In traditional port fuel injection systems, the pressure is lower, typically around 40 to 60 PSI. The fuel rail often houses the fuel pressure regulator or a fuel pressure sensor, which helps the engine computer monitor and control fuel delivery.
Fuel rails are solid components that rarely fail mechanically. However, the rubber O-rings that seal the injectors to the fuel rail can dry out and leak over time. A fuel leak at the fuel rail is a severe fire hazard, as pressurized fuel can spray directly onto hot engine components. Additionally, rust or debris inside the fuel rail can clog the injectors.
If you smell gasoline in the engine compartment or see wet spots around the injectors, the fuel rail and injector seals should be inspected immediately. Servicing the fuel rail requires depressurizing the fuel system safely before disassembly.