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An Inexpensive Locking Fuel Cap for Diesels

If a locking fuel cap is available for the diesel Hummer, I have not seen it. So, for those of you who have diesel beasts and wish to have some security over what goes into the fuel tank, I have made an inexpensive but effective fuel cap lock. This entire setup is purchased for less than $12. I don't think it voids our precious warranty. There are no patents for this nor are there any endorsements.

The list of materials is simple.

  • 6" hasp for a lock
  • 4 small screws that fit the four holes of the hinged part of the hasp
  • 1 small lock which fits around the Tee-handle of the fuel cap. (i.e. 1" x 3/16")
Look at the attached photos for end result. Use the photos as you read the instructions for installation.


  1. Cut off the end of the hasp through the portion that is slotted. File off any burrs and round the end with the file to avoid a nasty cut later. With a ball peen hammer form the end of the hasp that will be screwed to the fuel shroud. This involves making a slight curve in the hinged portion of the hasp. The hasp is now ready for mounting.

  2. Locate the hasp vertically in the shroud with the hinged end fitting snug against the shroud. Mark a hole for the lock on the hasp. I used a 3/16" for the small lock. Refer to the attached JPEG file. Mark the four holes for the screws.

  3. Drill the hole in the hasp. 3/16" or 1/4" is adequate.

  4. Drill out plastic fuel shroud for the four holes for the screws. If you remove fuel cap to drill the holes, stuff a rag in the fuel filler pipe to avoid getting drill filings in the fuel tank.

  5. Use the four screws to attach the hasp. Self-locking nuts and/or locktite should be used to make sure nothing comes loose.

  6. Install the fuel cap. The hasp swings out of the way. Turn the Tee-handle and make sure it is positioned vertical. Install the lock. The lock prevents the Tee-handle from turning and the forced removal of the cap if someone attempts to pull it out of the filler tube.
Simple, secure, and sweet.

By Myk Manon

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