There are many threads and videos on this repair but I thought I would throw my experience and info out there as someone may find it useful. It is a common problem for the fuel door on your F150 to become loose and flop around. The problem is usually caused by the hinge pin coming part of the way out that allows the spring to either come off or otherwise not have the proper leverage to fully close the fuel door. The fix is simple, but getting the darn part off the truck can be a pain. My solution was to purchase a set of cheap plastic trim/body panel pry bars. I picked these up for $4.99 on Amazon and had them in two days: Amazon.com: TCBunny® Portable 4Pcs Auto Car Radio Door Clip Panel Trim Dash Audio Removal Installer Pry Tool: Automotive First pull off the little "Easy Fuel" ring and remove the three bolts that attach the fuel filler pocket to the neck. Now you need to pop the tabs holding the pocket to the body panel. There is no need to contort yourself and try to push out the tabs from behind the fender. Just insert the tool under the rubber seal at the locations of the tabs and pop them out one at a time. The plastic pry bars will not scratch the paint. I started with the one at the 4:00 position, then moved to the 7:00 tab, then to 2:00 and finally 10:00. After you pop the first one, just hold that pry bar in place while you pop out a 2nd one. Once two are out the rest is easy. Here you can see what the tabs look like on the back side: The actual repair only requires something as simple as a small washer and a nail. Pull the spring and hinge pin out and then trim off some of the plastic on the bottom where the pin comes through, about 1/8" will do. I used a PVC pipe cutter but a dremel or file will probably work fine as well. Then, put the pin back in place and place a washer over it. Mark where to drill a 1/16" hole. Pull the pin back out, drill the hole, and then put it back together again. Put the washer back on, insert a small nail, and then bend the nail so that it stays in place. I didn't want to tweak the plastic pin too much so I grabbed one end of the nail with pliers while bending the other end with another pair. I cut the excess off the ends of the nail to clean it up. Pop everything back in place and it's better than new!