This process will vary slightly depending on the engine (small block, big block, etc.) and whether it's a carburetor or fuel-injected system. However, the general steps are as follows:
1. Preparation:
* Consult a Repair Manual: Obtain a repair manual specific to your 1985 Chevy truck and its engine. This is crucial for accurate instructions, torque specifications, and diagrams.
* Gather Tools: You'll need a socket set, wrenches, screwdrivers (possibly including a torque wrench), pliers, fuel line disconnect tools, jack stands, safety glasses, gloves, rags, and possibly a fuel pump installation tool.
* Drain the Fuel Tank (if possible): This significantly reduces the risk of spills. Siphon fuel carefully into an approved container.
* Disconnect the Battery: Disconnect the negative (-) battery terminal.
* Locate the Fuel Pump: The fuel pump is usually located inside the fuel tank (in-tank) on 1985 models. This means dropping the fuel tank is necessary, which is the most challenging part of the job.
2. Dropping the Fuel Tank:
* Safety First: Ensure the truck is securely supported on jack stands. Never work under a vehicle supported only by a jack.
* Disconnect Fuel Lines: Carefully disconnect the fuel supply and return lines. Use appropriate tools to avoid damaging the lines. Have rags ready to absorb any spilled fuel. You might need to relieve pressure in the fuel system by starting the truck for a moment *before* disconnecting the battery.
* Disconnect Electrical Connections: Disconnect the fuel pump electrical connector(s).
* Disconnect Tank Straps: Carefully unbolt the straps or clamps holding the fuel tank in place. There might be multiple straps.
* Lower the Fuel Tank: Carefully lower the fuel tank. It may be heavy and awkward, so have assistance if possible.
3. Fuel Pump Replacement:
* Access the Pump: The fuel pump is usually accessed through an access plate or by removing the sending unit from the top of the fuel tank.
* Remove the Old Pump: Follow the repair manual instructions for removing the old pump. Take note of how it's installed and oriented.
* Install the New Pump: Carefully install the new fuel pump, ensuring it's properly seated and oriented. Refer to the repair manual for any specific instructions or gaskets required.
* Reinstall Sending Unit (if applicable): If you removed the sending unit, carefully reinstall it, ensuring the float is free to move.
4. Reassembly:
* Raise the Fuel Tank: Carefully raise the fuel tank back into place.
* Reconnect Tank Straps: Securely reattach the fuel tank straps.
* Reconnect Fuel Lines: Reconnect the fuel lines, ensuring they are secure and properly seated.
* Reconnect Electrical Connections: Reconnect the fuel pump electrical connector(s).
* Reconnect the Battery: Reconnect the negative (-) battery terminal.
* Check for Leaks: Carefully check all connections for leaks.
5. Testing:
* Start the Engine: Start the engine and listen for any unusual noises from the fuel pump.
* Check for Leaks: Inspect the fuel lines and connections again for leaks.
* Verify Operation: Ensure the engine runs smoothly and doesn't stall.
Important Notes:
* Fuel Pump Compatibility: Ensure the new fuel pump is compatible with your truck's engine and fuel system.
* Fuel Pressure Regulator: If your truck has a fuel pressure regulator, it may need attention during this process.
* Professional Help: If you're not comfortable performing this repair yourself, take your truck to a qualified mechanic. This is a job that can be dangerous if not done correctly.
This is a general overview. Always refer to your specific repair manual for detailed instructions and safety precautions relevant to your 1985 Chevrolet pickup truck's model and engine type. Failing to follow these instructions precisely could lead to injury or damage to your vehicle.
