[edited 9/24/2018, 8/31/2020]
The hinge of the fuel-fill door contains a “stop”, for lack of a better term, that is pressed into position, and has been known to pop out of position on a few MX-5 and 124 Spiders, to be found as a mystery part(s), in the fuel fill cavity (presumably near the fuel overflow drain hole that is clearly shown in the bottom photo) upon opening the fuel door. The fuel-fill door will function fine without the stop, but will be subject to blowing around in the wind, while open, as the purpose of the stop is to keep the door in the open position, while fueling.
Hmmm, my fuel-fill door on my Toyota doesn’t stay put, maybe for a similar reason. (Research has since revealed, that Toyota didn’t incorporate any device for holding the fuel door open, at least in 2004; only a spring to pop it open.)
So, this is how duke8253 has reassembled the stop (John is wondering if the white piece is oriented correctly, as this orientation may explain why a few stops are popping out in the first place)…
I gathered my information for this article from an informative thread in the Miata.net forum, solving the mystery of what this part does, and where it belongs, and this Mazda diagram illustrates the removal procedure of the fuel-fill door assembly, in order to return the stop to it’s intended function…
… by removing the two bolts that fasten it to the car, and pressing the stop back into position. The painted nub of the plastic block needs to be pushed into the square hole in the fuel door arm.
- I just confirmed that the orientation in the second photo is how mine looks, and since it’s been fine for four years now, it must be “proper”.
- The top photo also does a great job of showing the stop properly installed, prior to bolting the entire assembly back into the vehicle.
- The next photo shows the other end of the stop, where the the white tube nests into a stop that is formed into the hinge…
FUEL-FILL CAP STIRRUP
On a side note, there is another part built into the fuel-fill door (not shown in the Mazda diagram above) that you may not be aware of – a stirrup to hold your gasoline cap while refueling that keeps it from swinging in the wind, and possibly marring your paint. So while refueling, both the fuel-fill door and the fuel-fill cap both remain where they belong, thanks to the stop and the stirrup.