If the "door" you try to open (it should be the big "safe/vault" type door with the ugnaught next to it in about the center of the level, that large structure surrounded by a chasm) using the "activate" key (you don't need to use any force powers to open it) makes a beeping (alarm) type noise, then it means the fuel has not been drained.
There should be a poster (several in the level) showing the fuel level on the tank. If the fuel is level with the green line, then it is ready, and the door should open if the T-shaped fuel wrench is in your inventory and you hit activate while facing the door (and you're close enough to touch it). If not, go to the fuel switches and be sure you get them in the right order to drain the fuel.
It may take some time to figure out which switches you have to throw, but you should get it. Just keep checking those posters.
Though it is supposedly linear, I actually had more trouble completing this level than just about any other SP level in JK. I still haven't ever beaten it with 100% secrets (oddly enough)!