Here's a general outline of the process. This is not a comprehensive guide and specific steps may vary slightly depending on your 4Runner's trim level and configuration. Always consult a repair manual specific to your vehicle year and model for detailed instructions and diagrams.
Safety First!
* Disconnect the negative battery terminal. This is crucial to prevent sparks.
* Ventilate the area extremely well. Work in a well-ventilated space or outdoors. Fuel vapors are heavier than air and can accumulate in low-lying areas.
* Wear safety glasses and gloves.
* Have a fire extinguisher readily available.
* Use only approved fuel-resistant containers and tools.
Steps (General Outline):
1. Prepare the Vehicle: Park on a level surface, engage the parking brake, and allow the fuel tank to nearly empty (for safety). This minimizes the amount of fuel you'll need to work around.
2. Access the Fuel Tank: This typically involves lowering the fuel tank. The process varies depending on the 4Runner's configuration (access from underneath, possibly requiring removal of exhaust components or other parts). Your repair manual will provide detailed instructions on this critical step. You might need to disconnect various components like the fuel lines, filler neck, and vent lines.
3. Drain Remaining Fuel: Carefully siphon out any remaining fuel into a suitable, approved container. Be extremely cautious during this step to avoid spills.
4. Disconnect the Fuel Sending Unit: Once the tank is lowered, locate the fuel sending unit. Disconnect the electrical connector and the fuel lines. There may be a retaining ring or screws holding the unit in place.
5. Remove the Fuel Sending Unit: Carefully remove the unit from the tank. Take note of how it's installed – you'll need this for reassembly.
6. Install the New Fuel Sending Unit: Carefully install the new fuel sending unit, ensuring it's seated correctly. Reconnect the fuel lines and the electrical connector.
7. Reassembly: Raise the fuel tank back into its position, reconnect all disconnected components (fuel lines, filler neck, vent lines, etc.). Double-check all connections for leaks before proceeding.
8. Reconnect the Battery: Reconnect the negative battery terminal.
9. Test the Fuel Gauge: Turn the ignition key to the "on" position (don't start the engine) to check if the fuel gauge is working correctly. If not, there might be a problem with the wiring or the new unit.
10. Check for Leaks: Start the engine and carefully check for any fuel leaks. Address any leaks immediately.
Important Considerations:
* Repair Manual: A factory service manual or a reputable repair manual specific to your 1999 Toyota 4Runner is essential. This will provide detailed diagrams, torque specifications, and step-by-step instructions.
* Fuel Line Disconnect Tools: Use appropriate tools for disconnecting the fuel lines to prevent damage and leaks.
* Fuel Pump: Depending on the design, the fuel pump may be integrated into the sending unit, requiring a complete assembly replacement.
* Professional Help: If you're uncomfortable with any part of this process, it is strongly recommended to seek professional assistance from a qualified mechanic. Working with fuel systems is inherently risky.
This is a complex repair job; taking your time, being meticulous, and prioritizing safety are paramount. Again, consult a repair manual and consider professional help if needed.
