Fuel pressure relief procedure

Warning: Gasoline is extremely flammable, so take extra precautions when you work on any part of the fuel system. Don’t smoke or allow open flames or bare light bulbs near the work area, and don’t work in a garage where a gas-type appliance (such as a water heater or clothes dryer) is present. Since gasoline is carcinogenic, wear fuel-resistant gloves when there’s a possibility of being exposed to fuel, and, if you spill any fuel on your skin, rinse it off immediately with soap and water. Mop up any spills immediately and do not store fuel-soaked rags where they could ignite. The fuel system is under constant pressure, so, if any fuel lines are to be disconnected, the fuel pressure in the system must be relieved first. When you perform any kind of work on the fuel system, wear safety glasses and have a Class B type fire extinguisher on hand.

Caution: After the fuel pressure has been relieved, it’s a good idea to lay a shop towel over any fuel connection to be disassembled, to absorb the residual fuel that may leak out when servicing the fuel system.

1. Unscrew the fuel filler cap to relieve any built-up vapor pressure in the fuel tank.

All except 6.0L V8 engines

Warning: The fuel delivery system on these models is made up of a low-pressure system (from the fuel pump in the tank to the high-pressure fuel pump on the engine) and a high-pressure system (high-pressure fuel pump, fuel rail and injectors). Once the pressure on the low-pressure side of the system has been relieved, wait at least two hours before loosening any fuel line fittings in the high-pressure portion of the system.

2. Remove the fuel pump control module fuses from the under hood electrical center (see Fuses and fusible links — general information).

3. Start the engine and allow to idle until it stops.

4. Attempt to start the vehicle two or three more times.

5. Turn the ignition off and disconnect the cable from the negative terminal of the battery (see Engine electrical systems).

6.0L models

6. Disconnect the cable from the negative terminal of the battery (see Engine electrical systems).

7. Unscrew the cap on the fuel pressure test port.

8. Surround and cover the test port with shop rags, then depress the Schrader valve inside the test port with a small screwdriver until the pressure in the fuel system is relieved. Properly dispose of the rags.

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