My dad had a 380SL many years ago of about that vintage that went through a few fuel pump relays pretty quick. I think replacing the pump ultimately fixed it. The relay was behind the front passenger kick panel. I took one of the relays that failed apart. A solder path had clearly been melted in half. I resoldered it and put it in the glovebox as a spare.

I would power the fuel pump directly and measure the current. It may well be that the circuit allows a current spike to fry the relays before a fuse does. If the fuel pump is one of those Bosch pumps mounted in the tank, I know from my SAAB days that they sometimes draw high current intermittently when they are starting to fail.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.