I did some quick searching and found these pages that talk at least a little about the OM636:

http://www.west-4x4.demon.co.uk/om636/om636e.html

http://en.wikipedia.org/wiki/Mercedes-Benz_W120/121

http://www.mbzponton.org/valueadded/technical/techdsl.htm

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.