Gack, my wife's 500SL strikes again. It really seems to be one of those cars that wants every repair done at least twice and repays kindness by pissing on your leg.
Anyway, I changed the fuel filter yesterday, pressurized the system - basically let the pumps run a couple of times until the turned off, cranked the engine for a couple of seconds without starting it, then let the fuel pumps build up pressure again and shut everything off. Checked everything over carefully and it was leak free.
Car then sat overnight on the charger as the battery is a bit weak. When I wandered into the garage in the morning it had stunk up the garage with gas fumes something horrible and there was a distinct wet patch right under the pumps. Backed out the car and it left a trail of gas 
.
On the ramps with the cover removed, there's a pretty obvious leak on the bottom pump as soon as we fired up the engine:
https://youtu.be/gXqELzaGUsg
Sorry for the crappy video quality, I used an older smartphone as I didn't want to ruin my good phone.
It's pretty obvious that the leak is between the fuel pump body and the banjo fitting. I figured I may as well check if the fitting was tight. After all, it's already leaking so I could hardly make it worse, could I?
I didn't, actually. The fitting was really tight, but when I fired it up again it barely leaked:
https://youtu.be/_y8IphubzZM
Err, what?
Anybody well versed in older Mercedes willing to comment?
The car did sit for about 6-8 months but it's never leaked gas during that time, nor before we laid it up.
). So no copper washers were reused as the fitting was never disassembled.
