[Peter Zimmermann]

OK, Let me try to explain this from memory with the caveat that I think the system changed for 1980 models.

The plastic tank has three hose nipples, two at the forward end, one at the rear. A hose should connect from the single, rear nipple on the car's gas filler inlet pipe near the gas cap (but inside the trunk).

The two nipples next to each other are different sizes, and a hose should connect the nipple on the gasoline tank to the larger nipple on the small plastic tank. WARNING, the hoses must be an exact fit, or fuel vapors might escape (clamps might not help if the hoses are the wrong size).

That leaves one nipple on the forward end of the plastic tank. A hose should come off that nipple, curve under the gasoline tank's filler pipe, and find it's way to a welded pipe fitting behind the fuse box. To find that connection it's probably best to disconnect the battery ground strap, then remove the fuse box screws and tilt the fuse box (leave all wires, fuses, and relays intact) away from the inner fender. You should be able to see a hose connection point, maybe even with an old piece of hose still connected. That hose will take your vapors out of the trunk and into the expansion chamber under the fender, above the w/washer reservoir.

Once you complete that connection behind/under the fuse box, you will have to jack up the car and verify that the hoses are connected properly at the expansion tank under the fender.