E300 D 1996 Big trouble Fuel leak
 

I decided to change the fuel lines and the injection line seals on my 1996 E300D (with 120K miles) because of a major fuel leak that was going on for few months.
I did purchase all lines, filter, prefilter, copper and rubber seals.
The job went smooth( it was not the first time). All is back together, car started no problem in about 30 sec of cranking.
After warm up I did took it for a spin....all great, and then I parked the car.
After 2 hours I discover a puddle of Diesel under the car.
Check every think and find out that diesel is leaking from the front driver side of the pump.See attached picture.What is that part that is connected with two fuel lines on the top and one on the bottom?

Also after I stop the engine the fuel line that goes from the prefilter to the valve on the head gets empty( no fuel inside). fuel line 32 from the picture

Line 32 draining back at shut down is normal.

The black valve is the Shut Off Valve. It has a $2 oring behind it that seals it to the side of the IP. The valve is about $200. Check that the fuel lines are clipped in place tightly and aren't the culprit first.

the fuel lines are attached firm to the shut off valve. I was noticing that "Click" when I pushed them in.
The other valve on the block seems to be wet as well ....

The metal "valve" further back is the lift pump. A leak there is probably being blown back or is again, a faulty fuel line seal. If the lift pump leaks it usually leaks engine oil.

Sounds like you need to waste a can of brake cleaner and get everything good and clean, then run it and check where its leaking from.