Ok...this is pathetic, but I can't help it...
I've drained all the fuel tanks (Jedi Knight Dark Forces II, Level 9) except for the last one on the level above the vault door. The problem is, the last one won't drain out. I flip the switch, but it just goes right back up again with no change in the fuel level. What in the name of Yoda's butt hole is going on here?!