The gas tank on my '71 Imperial is not delivering fuel. I'm going to have to lower/remove the tank to check it out. The tank has the 4 vents going into the vent-tank (not the vertical tube) at the front of the tank. Before I drop the tank, does anyone have any advice on what not to do when dropping the tank? Any special procedures to do or anything to look for in the venting system, or feed line? The factory manual doesn't have anything special to recommend.