I worked forward from the trunk with my mity-vac and found that my front passenger door has a leaky element. I also discovered that if the system has a leak the pump will "time out" and not work until it has been reset by disconnecting the battery or pulling fuse 13. That is why it was not coming on when I locked and unlocked the driver's door. Once I plugged the line to the passenger door and reset the pump all the other locks now work with the driver's door.

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine