Go to the dealer and get a "fuel connection renew kit." It has both O-rings, the Nylon spacer, and the Nylon clip that retains it all.
Theoretically, you replace that every single time you pull the fuel rail connection. However, that doesn't mean it won't just start leaking on its own as well (I suggest you get a spare to throw in the toolbox, so you're ahead of the game if/when this starts again. Yes, I know it's fifteen bucks - but it's still cheaper than an engine bay fire!)
To install:
- Remove fuel line by squeezing the ears on the retaining clip and pulling out. A pair of longnose pliers can help here.
- Using a small pick, remove the internal bits. You should get two rubber O-rings and a small Nylon ring as well. Check the end of the male part of the fitting - anything you find on there that isn't the Nylon retaining clip won't be in the female fitting, so you don't end up digging for something you won't find.
- Use a small flashlight and make sure the inside of the female portion of the fitting is clean and clear.
- Remove the renewal kit from the little bag and push it into the female fitting until you hear (or at least feel) it "click" into place.
- Squeeze the ears on the Nylon clip and remove the installation mandrel. The clip should stay in place (if it does not, no problem.)
- Remove the old Nylon clip from the male hose fitting. OK to be destructive.
- If the new clip came out of the female fitting, slip it onto the hose. Gently press it into place until it clicks over the tubing bead.
- Press the male fitting into the female fitting until it clicks into place.
Probably takes longer for me to tell it than it does for me to do it - it's really a simple job.