[Oldsguy]

Wow, that is a weird one. My guess is your guess is right, some previous owner bunged it up. I can't envision the hose going to the fuel pump. Maybe to a vacuum storage cannister. They are commonly used to hold vacuum created by the engine and are nothing more than a round, sealed metal can the size of say a frozen juice container or a little larger and they store vacuum for accessories when you stomp on the accelerator. Look for something like that on your firewall or inner fender and see if there are two nipples on it, one to the manifold vacuum and the other unused, that would be where your hose probably goes. As for the unused nipple on the fuel pump, I would say it would be pressure return line to vent the fuel tank, most cars have them. I say all this with a caveat because I very well could be wrong. I know the fuel pump is a pump and therefore might be able to create a vacuum that is used as plumbed, if that is the case then it might be a leaky/damaged pump. It may very well pump fuel but not create the vacuum needed. At any rate, good luck and let us know what you come up with.