I'm looking for some reassurance after some fuel line work on an 82 300cd. As I interpreted things, there are 2 hard, plastic fuel lines that come out of the firewall on the drivers side, almost directly above the power steering mechanism and below the brake fluid reservoir. One is the "supply", and sends fuel through the in-line filter. The other is "return", and receives fuel from the secondary, spin-on filter. Does anyone remember which of the hard, plastic lines is which; i.e., I think the top one (towards sky) is return, and bottom one (towards earth) is supply? I should have labeled them, didn't, and now am worried that I put things back together backwards. Would the engine even run if I had reversed that order? Thanks for any help.

I think you are confusing vacuum lines with the fuel lines. The fuel lines on the 123's are steel. They come from under the car and are attached to the driver's side fender well. The upper most line is the is the return and the lower one is the supply.

__________________

I definately had the material mixed up; I didn't realize that they were steel. Thanks for re-confirming the return=upper, supply=lower part.