empty and drop your tank..sounds like it's rusted or has something else in it..drop it and pull the top cover..you don't need a jack if you have a helper (these tanks are amazingly light)
(from my truck) note the 3' prybar..you'll need it most likely if your tanks are bolted like mine..the hangers hung on another set of bolts about halfway down and there wasn't enough room to get them off.
