Fuel leak diagnosis, video included

[colinsk8s]

Hello,

I have a 1985 260E (W124), Eurospec.

So I've had a fuel leak for a few weeks now, but it's a curious one. It only leaks when starting it cold after it's sat overnight. It only leaks for a short time, seemingly until fuel pressure has built up. But the small puddles under my car on the street from where I've started it cold have been growing larger, so I decided to investigate. I let the car sit for 24 hours, aimed my video camera and flashlight at the pump/filter area, and turned the key to the 2 second pump prime. Here's the video evidence:

Mercedes W124 Fuel Leak - YouTube

It appears to me the leak is coming from the diaphragm of the top fuel pump, which would mean it's shot. What do you see?

If the top pump is indeed shot, my next question is do these pumps have to be changed in pairs, or can I keep using the bottom one.

I also plan to replace both check valves as well as the filter.

Thanks for your time!
Peace,
Colin.