There are a couple of ways to relieve the fuel system pressure in the Ford F-150. The basic way is to disconnect the fuel pump relay, crank the engine and starve the lines of fuel. The other method involves using a fuel gauge on the Schrader valve located along the engine's fuel rail. The Schrader valve covers the fuel pressure test port. Relieving pressure in the fuel lines is necessary if you want to service any component of the fuel system, such as the fuel pump or filter. The procedure is the same in all F-150s with a Schrader valve and fuel test port.
Shut off your F-150's engine. Open the truck's hood. Let the engine cool down for about 20 minutes.
Grab your fuel gauge, bucket and shop rags. Inspect the passenger side of the engine compartment to find the Schrader valve. Look on the left-top side of the engine to find the fuel rail. On the fuel rail, you'll see the Schrader valve. It usually has a yellow cap and looks similar to a tire valve. Unscrew its cap.
Connect the fuel gauge to the fuel gauge test port. Push the connection on firmly. Run the fuel gauge drain wire into your bucket just in case any fuel leaks.
Push the "Release" or "Relieve" button on your fuel test gauge to relieve the fuel system pressure. A small amount of fuel may leak into the bucket. If you spill any fuel, clean it up with the shop rags and wash yourself well. Replace the Schrader valve cap and proceed with your repair.
