Most Sequential Fuel Injection (SFI) engines , except 2004 4.6L SOHC engines, are equipped with a pressure relief valve located on the fuel supply manifold. Remove the fuel tank cap and attach fuel pressure gauge T80L-9974-B, or equivalent, to the valve on the fuel rail. Place the tube from the tool into a small container and open the valve on the tool to release the fuel pressure. Be sure to drain the fuel into a suitable container and to avoid gasoline spillage. If a pressure gauge is not available, disconnect the vacuum hose from the fuel pressure regulator and attach a hand-held vacuum pump. Apply about 25 in. Hg (84 kPa) of vacuum to the regulator to vent the fuel system pressure into the fuel tank through the fuel return hose.
For 2004 4.6L SOHC engines, remove the fuel pump fuse; located in the engine compartment fuse box. Start the engine and allow it to run at idle until it stalls. After the engine stalls, crank the engine for approximately five seconds to ensure the pressure in the fuel injection supply manifold has been released. After the fuel pressure has been fully released, turn the ignition switch to the -OFF- position.