behind the back seat (wagon), or on the floor of your trunk (sedan), there's an access plate in the floor, removes with a couple 3-4 screws. under that plate you can see the gastank access, there's a large plastic threaded ring, probably has a big hose clamp around it (that was an engineering mod they made sometime in the late 80s), and this ring secures the tank access plate. it has the gas filler tube, the tank vent plumbing that goes to the carbon canister, the main gas line, the gas return line, and a few wires. under that panel and attached to it are the in-tank fuel pump, and the gas tank level sender.
this article shows the gory details of getting in there.
its talking about a Regina system used on some 740/940's, which only have a single in-tank pump and no external pump, but other than the exact in-tank pump type, they are otherwise the samea s the Bosch systems.
on a 7/9 wagon, fold the back seats down flat, and lift up the front edge of that floor flap that goes behind the seats and you'll see 3-4 nuts (under both panels), remove those and the floor panels lift out, exposing the gas tank access panel... otherwise, its pretty much the same as the 740 sedan shown.