Which is fuel out and which is fuel return 1985 300SD tank

[coachgeo]

I did not even know where to start to search for this answer. My appolgies for that.

If anyone has an idea on what key word(s) to search by I'll be happy to.

What Im trying to get answered is... when laying on your back under a 300SD... which fuel line is which? It appears the fuel lines go up from under the car into the tank area on the passenger side.

What line is it on the driver side that goes up into tank/trunk area. Looks to be a valve (or filter?) on it. Im guessing a vacuum line (though its rather large for that) for something like maybe the automtatic antena?

Im not getting fuel to the engine. I have manually (mouth) sucked on the fuel line till I was blue in the face (thru an electric pump) and I get little to nothing. Pump turned on.. (not primed well) cant seem to pump anything up either.

Want to know what line to pull back there and blow thru to see if the tank screen is clogged. Might put an electric pusher pump back there too for a while and by pass an aging OEM lift lift/primer pump. Any cautions/concerns with that idea?