For future searches, I thought I'd jot down some notes. As I searched the threads, many tips came but they came from different threads:

PROBLEM: my fuel lines were rusted and leaking near the rear axle (1985 300TD)

SOLUTION: (without drowning in fuel)

1. clamp the hose a couple inches from the tank (either the sending line or receiving line - one at a time)
2. locate a spot foward on the fuel line where the line is not corroded where a splice will take place
3. roughly measure the replacement fuel line (i used rubber and 7.9mm from Auto Zone - worked great)
4. plug one end of line with a golf tee and feed it from the eventual splice spot, up and through the body (following the old line)
5. when the line is in place, cut the metal line where the splice will take place and catch the draining fuel in a bucket. Not too much will drain as the hose is clamped.
6. feed the new rubber line on after cleaning the metal receiving end and clamp it down
7. remove clamp from old rubber hose protruding from fuel tank and put finger over hole to stop fuel.
8. feed new line onto metal fitting and clamp tight.

On my return line, I spilled about a teaspoon full and on my sending line, about a half-cup. I did this with the tank full because the leak was starting to get on my nerves.

Hope this helps.

Don

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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed