Here's a general outline. Specifics may vary slightly depending on your truck's configuration and the exact type of fuel selector switch installed. Consult a repair manual specific to your 1990 Ford F-150 for detailed instructions and diagrams relevant to your exact model.
1. Preparation:
* Disconnect the negative battery terminal: This prevents accidental sparks and shorts.
* Gather tools: You'll likely need a socket set (possibly metric and standard), screwdrivers (Phillips and flathead), pliers, and possibly a fuel line disconnect tool.
* Locate the fuel selector switch: It's usually located near the fuel tank, often under the vehicle. Your repair manual will show the precise location.
* Protect yourself: Wear safety glasses and gloves.
2. Accessing the Switch:
* This will likely involve getting under the truck. You might need to use jack stands for safety. Never work under a vehicle supported only by a jack.
* You may need to remove some components to access the switch, such as the bed or other parts of the undercarriage. Again, your repair manual will provide detailed instructions.
3. Disconnecting the Fuel Lines and Electrical Connections:
* Fuel Lines: Carefully disconnect the fuel lines from the selector switch. These lines are under pressure, even when the engine is off. Use the appropriate fuel line disconnect tool to avoid damage or leaks. Have rags or shop towels ready to absorb any spilled fuel.
* Electrical Connections: Disconnect the electrical connectors from the switch. Note the position of each connector before disconnecting to ensure correct reassembly. Take pictures if needed.
4. Removing the Old Switch:
* The switch is usually held in place by bolts or screws. Carefully remove these fasteners.
* Once the fasteners are removed, gently remove the old switch.
5. Installing the New Switch:
* Position the new switch in the same location as the old one.
* Attach the mounting bolts or screws.
* Reconnect the fuel lines. Ensure they are securely connected and free of leaks.
* Reconnect the electrical connectors, matching them to their corresponding locations.
6. Testing and Reassembly:
* Carefully lower the vehicle (if raised).
* Reconnect the negative battery terminal.
* Check for leaks: Carefully inspect all fuel line connections for leaks. Start the engine and check the fuel gauge and fuel selector switch to ensure it's operating correctly.
* If everything is working properly, reassemble any removed components.
Important Considerations:
* Fuel Pressure: The fuel system may still have some residual pressure, even after disconnecting the battery. Take appropriate precautions to relieve any pressure before disconnecting the fuel lines.
* Fuel Type: Ensure the new fuel selector switch is compatible with your fuel type (gasoline or diesel).
* Repair Manual: A repair manual specific to your 1990 Ford F-150 is highly recommended. It will provide detailed instructions, diagrams, and torque specifications for your specific model.
This is a general guide. Improper installation can lead to fuel leaks and potential fire hazards. If you are uncomfortable performing this repair yourself, it's best to take your vehicle to a qualified mechanic.
