I don't think a blockage would cause the thing to be dry.
Fuel should get to any point in those lines from both sides. In other words, if you take the return line loose from where it attaches at the fuel filter and run the car you should have fuel coming out of both the line and where it connected. It should not have pressure (from the filter)though as this is a fuel return line.
If you wish to verify the flow, take the line from the filter as above and plug the filter side. Place the end of the rubber line into a container and run the motor. A small flow of fuel should come out.
To assist in determining the exact leak source, get a can of brake clean and spray off an area. It will leave a very dry area. Watch closely after someone else starts the engine. You might want to do this on a cold motor. I have sprayed that stuff on about everything but the product can vary in composition and they are all very flammable (usually mostly alcohol).
[Edited by stevebfl on 07-07-2001 at 11:38 AM]
Bosch Master, ASE Master, L1
33 years MB technician