Reassembly
With the cylinder installed and working and the cylinder cap on, you can put the rest of the cap back together. Make sure that the parts of the venting system are still present and installed correctly (refer to photos). Place the 6 springs back on the pegs. Assemble the main cover as follows. First the metal ring with grooves down. Place the rubber gasket on top of it, so the wide flange is facing up. The place the plastic cap on top of that with the 4 holes toward you. Orient it such that the small hole that does not have screws going in it is to the right, when the hinge of the assembly is at 6 O’clock.
Place the latch assembly on top of the main cover to line up the screw holes, plate down. There is a slight dimple to indicate which orientation. Then tighten the two screws.
If you are installing a new gas cap (not replacing an existing one), take note that there is a small, round, 12mm gasket on the underside at 7 O’Clock. This part is NOT included in the new gas cap assembly and must be moved to the new assembly before installation. It provides a seal with a metal tube on the tank.
WARNING: Before closing the gas cap on the tank, TEST IT AGAIN A FEW TIMES to make sure the key and latch are working correctly. If they are not and you close the cap, you will NOT be able to open it ever again without drilling out the cylinder!
For me, the results were simply amazing. Finally almost no resistance to opening and closing.
Lubrication
Most of my focus in the past has been on the latch- cleaning and lubricating it. And that does solve the majority of the issue with this cap becoming stiff over time. However, the cylinder plays a role as well. And if you, like many people, have shot various lubricants in the cylinder over the years, it is likely to gum up the works and will need cleaning. So if you plan to really clean the assembly, it requires also removing the cylinder to clean that, too. And if you are replacing the whole assembly, you will need to either order a new cylinder and then either rekey it to match your ignition key, leave it on a separate key, or you will want to clean and move the old cylinder to the new gas cap.
One of many discussions is what to use as the correct lubricant for both the latch and also the cylinder. First I will discuss either dry or wet graphite. Don’t do it, not for the lock nor the latch. Although graphite can be a great lubricant for some types of locks, those in a vertical orientation and especially around gas and in a wet environment is not a good combination. For one, it is messy as hell. And over time, it will gunk. And if it gets wet or you use some OTHER wet lubricant later, it will make things worse. I believe that WD-40 and regular light oil are also not good because they leave too much residue and will attract debris and the inevitable corrosion. Same for using lithium grease on the latch. After much research, I decided I will use a dry teflon spray (PTFE). It is almost no mess, attracts no debris, lubricates well, is very inert, supposedly leaves a film of anti-corrosion, and lasts a long time.
Of course, when I went to try and get some, nobody had any (typical). Since I didn’t plan well, I decided to just blow out the WD40 from the cylinder, not lube the sides of the cylinder, and just leave the factory oil lube in the new latch. I will revisit it later if/when needed.