Can’t get power past fuel pump relay?
Looking at the wiring diagram for the Fuel Pump Relay. Black wire should be grounded. The Red/Yellow wire should be battery positive when activated and will connect power from the Yellow wire and flow through the Pink/Black wire to feed the fuel pump. If you are not seeing battery positive on the yellow wire, check the Inertia Switch.
Two electric pumps are used on fuel injected models; a low pressure boost pump mounted in the fuel tank and a high pressure pump mounted on the vehicle frame. Some models equipped with the 8-460 (7.5L) carbureted engines use a single low pressure pump mounted in the fuel tank.
On injected models the low pressure pump is used to provide pressurized fuel to the inlet of the high pressure pump and helps prevent noise and heating problems. The externally mounted high pressure pump is capable of supplying 15.9 gallons of fuel an hour. System pressure is controlled by a pressure regulator mounted on the engine.
With internal fuel tank mounted pumps tank removal is required when servicing the pump. Frame mounted models can be accessed from under the vehicle. Prior to servicing release system pressure (see Fuel Supply Manifold details). Disconnect the negative battery cable prior to pump removal.