The fuel today is supplied to the engine by the Electric GMC Fuel Pump for all vehicles that are rolling off of the assembly line. This is the replacement for the mechanical fuel pump that is n longer used because of the requirements of the new fuel injection systems being used.
The ability of the electric fuel pump to deliver a constant and stable level of pressurized fuel to the cylinders is why the engine can operate at its peak capacity and efficiency. The older mechanical versions are not built to provide this level of consistency and cannot longer be used on modern GMC trucks.
The location of the electrical fuel pumps is in the fuel tanks on most models. This makes it possible for the electrical fuel pump to push the fuel forward towards the GMC engine and the fuel injectors. By being in this position it is possible to more precisely regulate the pressure and volume of the fuel being delivered.
What should be remembered by the GMC owner is their fuel system is pressurized by an electrical fuel pump. This is to say every time the ignition key is turned on the fuel system becomes instantly pressurized. If there is any work to be done to the fuel system, the ignition key should be removed so it cannot accidently activate the fuel pump for any reason causing fuel to be sprayed out of this closed loop system.
Because of where it is placed on your vehicle, the electric GMC fuel pump can only be replaced once the fuel tank has been lowered and removed from the vehicle. While this might be time consuming, it will occur less often then the replacement of the older mechanical ones of the past.