Have you checked the ground wire of your fuel pump? I think the ground is shared with the ground for the electric antenna (in the trunk, driver's side wheel well). We had the same problem with my father's 190E, when the key was turned to start the car, you could barely hear the fuel pump work for about half a second. Afterwords, nothing. Once we found the groung to be loose, we tightened it. Then the car started without hesitation. I hope this helps.
'82 300D Turbo 216k miles