Basically the cable should start pulling at the same time as the inj pump starts moving. This isn't the same thing as linkage movement. A number of activities take place before the pump starts moving.
The hard thing about finding a tech for making these adjustments is that they are old cars now and most of the adjustments weren't as necessary after 1985. My main MB transmission tech leaves these adjustments to me as I have been doing them nearly twenty years at 2-5 a week.
If you get a wild hair to learn your beast let me know; I have writen a number of long posts about it.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician