1. Preparation:
* Gather Tools: You'll need sockets (various sizes), wrenches (including a fuel line wrench if possible), screwdrivers (Phillips and flathead), pliers, a hammer, a fuel pump pliers (optional but helpful), safety glasses, gloves, rags, and possibly a fuel tank hoist or straps if you're removing the tank. A shop manual specific to your 1972 Chevy truck model is highly recommended.
* Safety First: Work in a well-ventilated area. Gasoline fumes are explosive. Use caution around the fuel tank and lines. Have a fire extinguisher nearby.
* Drain the Fuel Tank: This is crucial. Siphon or drain as much fuel as possible from the tank.
2. Tank Removal (Usually Necessary):
* Access: Locate the fuel tank. It's usually under the bed, accessed through a removable access panel. Consult your shop manual for the specific location and access procedure.
* Disconnect Fuel Lines: Carefully disconnect the fuel supply and return lines. Use fuel line pliers if you have them to avoid damaging the lines. Have rags ready to absorb any spilled fuel. Mark the lines to ensure correct reinstallation.
* Disconnect Electrical Connector: Disconnect the fuel sending unit's electrical connector.
* Remove Tank Straps/Hold-Downs: Carefully remove the straps or hold-downs securing the fuel tank.
* Lower the Tank: This is where a tank hoist or strong straps are very helpful. Lower the tank carefully and support it to prevent damage.
3. Sending Unit Removal and Installation:
* Locate the Sending Unit: The sending unit is typically mounted inside the fuel tank.
* Remove the Old Sending Unit: This often involves removing nuts or bolts securing the unit to the tank. It might also involve removing a retaining ring or other fasteners. Your shop manual will show you the specifics.
* Clean the Tank: Use a clean rag to clean the area where the new sending unit will be installed. Any debris can interfere with a proper seal.
* Install the New Sending Unit: Carefully install the new sending unit, ensuring a proper seal and tightening all fasteners according to the manufacturer's instructions and your shop manual.
* Test the Float: Before reinstalling the tank, test the float in the sending unit to ensure it moves freely and is not binding.
4. Reinstallation:
* Raise the Tank: Carefully raise the fuel tank back into position using your hoist or straps.
* Reconnect the Fuel Lines: Reconnect the fuel lines, ensuring they are properly seated and secured. Double-check your markings.
* Reconnect the Electrical Connector: Reconnect the electrical connector to the sending unit.
* Secure the Tank: Secure the tank with its straps or hold-downs.
* Reconnect the Battery: Reconnect the negative battery terminal.
* Check for Leaks: Check for any fuel leaks around the fuel lines and the sending unit.
5. Testing:
* Start the Engine: Start the engine and check the fuel gauge. The gauge should now read correctly.
* Check for Leaks Again: After running the engine for a short time, check for leaks one more time.
Important Considerations:
* Shop Manual: A shop manual specific to your 1972 Chevy truck is essential. It will provide detailed diagrams and instructions specific to your model.
* Fuel Pump: If you're replacing the fuel pump as well (a common practice), you'll need to handle that during the tank removal and reinstallation.
* Tank Seal: If the fuel tank's gasket or seal is damaged, replace it.
* Professional Help: If you're uncomfortable with any part of this process, it's best to seek professional help from a qualified mechanic.
This is a general guide. Specific steps may vary depending on your truck's exact model and configuration. Always consult your shop manual for precise instructions and safety precautions. Remember safety first!
