O.K, the other goof up I had happen earlier today, and this one was my fault and involved Superblack (my '92 5.3, 
) involved checking the condition of the fuel level sender, since we are having what appears to be an inaccurate reading on the gauge (i.e. full tank and yet gauge shows less than 1/4 tank). Relying on memory from when I actually r/red a bad sender myself in Supercat, my '95 4.0 coupe that I used to own several years ago, I did not believe it was necessary to drain fuel from the tank before the procedure. I clearly recalled that when I removed the retaining ring (after purchasing a $$$ brass hammer and set of drifts, āper the bookā, for safety) no fuel came out of the open access hole at the time. I was thinking this was b/c the tank was designed so that even when technically āfullā (per the gauge, the level of fuel in the tank is actually some distance below the access hole. 
I was therefore assuming that Superblackās tank would be ditto. Wrong-o! 
As my tech bud, who had argued with me on this point earlier, suddenly discovered upon knocking Superblackās retaining ring for the sender assembly loose with a rubber mallet, my argument was incorrect, as fuel immediately started leaking out rapidly past the sender unit and the hole gasket. 
Fortunately, he was able to very quickly get the retainer back on and wipe up the small amount of fuel which leaked out and down the face of the tank with paper towels. 
Checking the Jag factory service repair literature after this scary event, It does not provide an actual procedure for r/ring just the fuel level sender. The only thing remotely related is r/ring the whole fuel tank itself, which, given that you have to disconnect fuel lines from same (some of which attach near/at the bottom), it would make sense to siphon out all the fuel first with that operation. Iām thinking what happened here is there are two different designs of tanks between the two models of XJS (seems like the '95 4.0 coupeās was mounted vertically vs. the '92 5.3 coupeās being more āhorizontalā ?) Or, possibly I just got lucky with my 4.0 experience and the fuel level in the tank at the time was indeed very low. ? 
Anyway, learn from my mistake and donāt repeat it, yaāll ā¦ 