on my 1992 300d 2.5, the hard injection line from the injection pump to the injector broke just above the nut at the injector on cylinder 5. So I order one directly from Mercedes dealer for $68. Two other dealers in the area had it for $112. So I got a deal right? I put the line on as I was actually able to just snake it around everything. After tightening everything down, fuel was leaking around the top of the nut again at the pump. Its a compression fitting so I'm thinking I screwed that up. Another $68 for the part from the dealer and I put the second one on. I tighten it lightly and start the engine. ITS LEAKING. I tighten more and more and still can't stop the leak.

What's going on here? I asked if there was a O-ring, but the parts guy says no.

Anyone have any ideas?