How to Repair a Fuel Cap How to Repair a Fuel Cap

What You'll Need
Needle nose pliers
Rubber gasket
Lacquer thinner


A fuel cap for an automobile is made of metal or plastic. It secures the entry to the fuel tank. Mostly the caps have threads, which are fixed to the tank pipe with matching threads. A rubber gasket at the top gets compressed when the cap is fixed and stops the leakage of fuel. The gas cap has air vents to allow the air to enter into the tank for maintaining pressure.

Generally, gas caps can be used as a closure for the fuel tank.

On the latest cars, the emission control has an engine light, which turns on when there is leakage. If the seal is damaged or the cap cannot properly seal the tank, the lights will glow continuously.

Check that the gas cap is present and screwed on properly. Most of the time, the problem may be solved by replacing the defective gasket. However, cleaning the cap and/or greasing the gasket may also help in a few cases. Here are a few steps to help you repair the fuel tank cap.

Step 1- Find the Specs for the Replacement Gasket

Check your car manual to find specs for the fuel tank cap and its gasket and check with supply store to get the right type of cap gasket and cap for your car.

Select a suitable gas cap gasket. Do not try to substitute it with another type, even if it looks similar.

Step 2- Find the Problem

If the fuel tank cap has ventilation problems, then you may be able to repair your old cap. However, it will depend on the design and make of your vehicle

Step 3- Locate the Orientation Mark on the Cap

Find the orientation marks on the top of the cap. It is a white dot on the edge of the cap. Before disassembling the cap, mark on the bottom side of the cap using a pencil.

Step 4- Remove the Bottom Part

Unroll the edge of the bottom part of the gas cap with a pair of needle nose pliers to separate it from the cap. The cap has three portions: top, middle and bottom.

Step 5 - Disassembling the Cap

Disassemble the gas cap parts. Make a sketch before removing the parts and mark them for easy re-assembly. The inside portion will disassemble into numerous parts to reveal the valve and spring etc. There are O-rings also. These parts cannot be purchased separately.

Step 6- Observe Any Dirt or Corrosion

Open the parts. You may find a lot of orange sticky fuel residues on the parts. Wash them with lacquer thinner to remove the residue.

Step 7- Reassembling

Dry the parts after cleaning and washing. Reassemble the cap inside portion. Insert the top and the bottom portions. Keep pressure on the lower part when rolling its edge over the top to properly position the o-rings. Replace the gasket if it is cut, squeezed or damaged.

Step 8- Grease the Gasket

The gasket becomes hard with time. Many times, the old gasket can work by applying some lubricating grease on its face. However, it will work only for a short time. Put the cap on the fuel tank.

Got a New Project You're Proud of?

Post it on Your Projects!