How to Fix a Gas Tank Rupture in a 1966 Mustang

Ford Motor Company made very little changes to the Mustang for the 1966 model year. The gas tank placement was still at the rear of the car in between the frame rails. Like the Falcon on which the Mustang is based, the top of the tank forms the bottom of the trunk floor. The tank is removed through the trunk compartment -- not the underside of the car -- when repair or replacement is necessary.

Instructions

Open the hood. Loosen the negative battery cable with a wrench. Twist the cable off the negative battery terminal and push it to the side. Remove the fuel filler cap.

Place a drain pan under the drain plug on the passenger side front corner of the fuel tank. Place the pan under the rubber hose fitting of the fuel sender at the center of the front of the tank if there is no drain plug present. Ensure the pan is large enough to hold the remainder of the gasoline in the tank.

Remove the drain plug with a 3/8-inch wrench. Allow the fuel to drain into the pan. Replace and tighten the plug once the tank has emptied. Skip this step if the fuel tank on your Mustang does not have a drain plug.

Loosen the hose camp on the rubber hose fitting to the sending unit at the center of the front of the tank with a Phillips screwdriver. Slide the camp away from the fitting a few inches. Pull the hose off the fitting on the sending unit. Allow the fuel from the sending unit to drain into the drain pan. Leave the hose off the sending unit.

Pull the wiring connector -- located next to the rubber hose fitting -- straight off the sending unit.

Remove the four retaining screws from the fuel filler pipe flange on the back of the car with a 5/16-inch socket and ratchet. Open the trunk lid. Remove the nut from the gas cap tether cable with a 7/16-inch socket and ratchet from inside the trunk compartment. Pull the tether and cap straight off the back of the car and place it aside.

Loosen the clamps on the hose that connects the fuel filler pipe to the top of the gas tank with a Phillips screwdriver. Pull the filler pipe off the hose. Pull the filler pipe straight out of the back of the car.

Remove the spare tire and tire changing tools from the trunk. Pull up and remove the trunk mat.

Remove 11 of the gas tank retaining screws from the perimeter of the tank in the trunk floor with a 3/18-inch socket and ratchet. Remove the remaining screw -- which is doubles as a bumper bracket bolt -- with a -inch socket and ratchet.

Have a helper push up on the tank from the bottom of the car. Lift the tank straight up from the trunk floor. Remove the tank from the car through the trunk compartment.

Clean the area around the rupture in the tank with brake cleaner and a rag. Follow the directions for a commercially available fuel tank repair stick to plug the hole caused by the rupture. Replace the tank -- reproduction units are available for approximately $100 as of 2012 -- if the rupture is too large to be repaired.

Position the tank into the trunk compartment with the flat side facing upward and the fuel filler hole facing the rear of the car. Use a helper and lower the tank slowly into the opening in the trunk floor until the mounting flange on the tank rests on the mounting surface of the trunk floor.

Replace and tighten the gas tank retaining screws. Feed the gas tank filler pipe through the hole on the outside of the car and into the trunk compartment. Push the rubber hose over the pipe and tighten the clamp.

Replace the gas cap and tether and tighten the retaining nut. Replace the four retaining nuts on the fuel filler pipe flange and tighten them. Replace the fuel filler cap. Replace the trunk mat, spare tire and tire changing tools.

Push the rubber hose back onto the fuel sending unit fitting and tighten the clamp. Push the wiring connector back onto the terminal on the fuel sender.

Add just enough fuel to the tank using a funnel to get the car to a gas station. Check underneath the tank around the repair -- if applicable -- and the fuel sender hose fitting for leaks. Replace and tighten the negative battery cable.