To remove a mechanical pump, start by detaching the cable from the negative battery terminal and removing the fuel tank filler cap to relieve fuel pressure. Then, wrap shop towels around the fuel pump inlet hose and outlet line fitting to absorb any spilled fuel. Detach the fuel inlet hose and outlet line fitting from the fuel pump, and unscrew the fuel pump mounting bolts to remove the pump and gasket. Scrape away any old gasket material from the fuel pump and engine block sealing surfaces. For models before 1988, the fuel tank needs to be removed. Relieve the fuel system pressure, detach the cable from the negative battery terminal, and raise the vehicle on jackstands. Disconnect the fuel vent, supply, and return hoses from the fuel pump/sending unit fittings, and detach the electrical harness connector. The fuel pump/sending unit assembly is located inside the fuel tank and is held in place by a cam lock ring mechanism. To unlock the assembly, turn the inner ring counterclockwise until the locking cams are free of the retaining tangs. Gently tap the rings loose if they are difficult to release. Extract the fuel pump/sending unit assembly from the fuel tank, being careful not to bump the fuel level float and sending unit. Inspect the condition of the gasket around the lockring mechanism and the inside of the tank. Clean the tank if sediment is present. If replacing the fuel pump, ensure you get the correct pump. To disassemble the pump, remove and discard the fuel pump inlet filter, detach the fuel pump wires, and remove the fuel pump outlet hose and clamp. Replace the hose if necessary. Remove the fuel pump top mounting bracket nut and remove the fuel pump. Reassemble the pump by installing a new inlet filter, placing the fuel pump top mounting bracket over the pump, and positioning the fuel pump in the lower bracket. Slide the stud of the top bracket through the hole in the fuel pump side bracket and tighten the top mounting nut. Install the fuel pump outlet hose and secure it with new clamps. Connect the wire terminals to the motor. To install the pump, insert the fuel pump/sending unit assembly into the fuel tank and turn the inner lock ring clockwise until the locking cams are fully engaged. Attach the cable to the negative battery terminal and start the engine, checking for any leaks.