Edit "its not too bad to drop the tanks"-I missed the word "not" in my first post. Sorry for the confusion. The selector is supposed to completely separate the two tanks, making them independent systems. When it goes bad, it lets pressure out into the tank that isn't running. If one fuel pump is going bad, then the other tank will run completely normally, the front pump on our truck has been dead for a couple years now, but I changed the rear one a few years back so we aren't too worried about it, just means more frequent trips to the gas station.