Anyone who thinks MB does poorly on technical data ought to have been fixing them in the 70's. The service info on the 108 chassis is the pits. The wiring diagrams were all on one page. This makes pulling individual circuits out a real pain, BUT to make matters worse the trans control, power windows, A/C, and any emissions electrical was left off. Only the basic car as sold in Europe was included.
The diagrams were included in the 108,109,111,113 chassis manual which you should look for on ebay. With the manual you will also get some of the other wiring in the section pertaining; such as A/C. It also has a fair description of the governing mechanism on the injection pump.
Bosch Master, ASE Master, L1
33 years MB technician