To complete an automobile fuel tank repair, first use a car jack to safely raise the car to a height that allows placement of jack stands under the car, then place jack stands underneath the vehicle. Locate the fuel tank leak, and use sandpaper to sand 1 1/2 to 2 inches around the hole. Use alcohol to clean the sanded area. Mix gas tank repair epoxy to the manufacturer's instructions, apply into and around the hole, and allow to dry.
Before applying the epoxy to the leak, shape an inch-long portion into a cone with a wide base. Insert the tip of the cone into the hole as far as possible. Use the remaining epoxy to cover the entire sanded area. A small amount of water helps the epoxy bind to the sanded area and smooth easier.
After the epoxy dries, remove the jack stands, and lower the car to the ground. Fill the gas tank and check for leaks.
Epoxies are available at auto parts stores. They are water-resistant and are not compromised by gasoline, diesel, or kerosene. They are usable on both metal and plastic tanks and suitable for fuel tank, coolant, radiator or oil pan repairs. When applying epoxy, use protective eye wear and gloves. Wash exposed skin with soap and water to remove.