Wow! Great info, gmog. As usual. I, too, have never heard that pump running on my 97 E300. I guess the sound deadening is doin its job!
Currently at the MB dealer lookin into a new fob/key. Always educational! Turns out the 95 fob is different than the 96 which is different from the 97, etc. They are not interchangeable, of course. My '97 fob/key is $245. There were ONLY 17 left, nationally. After that, NLA and SOL. It arrives programmed and the key cut. I also ordered the flat "master key". It is $45. Not cheap, but my only working fob has seen better days and is ready to blow up like an over wound clock! Too bad the PO didnt take better care......