IMHE, if the fuel pump relay acts up, it will simply kill the engine. Same-o with the coil - you would not be able to keep the engine alive with the gas pedal and the brake.

With that said, this is very similar to a problem that I had with my 300E. I'd suggest replacing the air flow pot. Lots of posts on this.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe