Fuel pump relay is a common failure. The test for the relay tests the inputs, not the relay. Easy to replace but not cheap. My 107 Euro has it located behind the glove box. Just remove the glove box light, then with a plastic wedge, remove the fasteners and pull out the glove box. It's a 5 minute job. Pull out and push in a new relay and you're done. Then, if it's not the relay... You might get an amp test on the fuel pump to make sure it's still good too. My $0.02 and worth it.

Steve
'85 SL500 Euro