Fuel Tank Filler Neck
The metal or plastic pipe that connects the gas cap opening to the fuel tank.
The fuel tank filler neck is the pipe that routes fuel from the fuel door opening down into the gas tank. It features a threaded neck at the top for the gas cap and a connection point at the bottom where it joins the fuel tank.
Filler necks are subject to rust and corrosion, especially in regions that use road salt, because water and debris can collect behind the fuel door fender liner. A rusted filler neck can develop pinholes, allowing fuel vapor to leak out and water or dirt to enter the fuel tank.
A leak in the filler neck will trigger a check engine light for an EVAP system leak (such as code P0456). In severe cases, dirt entering the fuel tank through a rusted filler neck will clog the fuel filter and damage the fuel pump, requiring replacement of both the filler neck and the fuel pump.