All of these bosch MFI(mechanical fuel injection) pumps are set up the same.Get the engine to number one top dead center.It should align with the marker on the damper.The cam should align with the notch on the cam washer and the lump(line) on the first cam bearing stand and distributor rotor on number one spark plug lead.
turn the MFI until the mark on the splined coupler aligns with mark on the housing,that is number one injector posistion,carefully slide the pump into place.It should now be timed.
If the timing chain is worn you will never ever get max performance from your engine.I always replace the timing chains and tensioner (if obtainable) and do it with the pump in place.check pump timing after chain is replaced and you will see the timing will need adjusting again.
Check your fuel flow by connecting the pump in the rear to 12volts(turn on the ignition),at the MFI it should pump a minimum of 1 liter in 15 seconds.These pumps are flow devices so pressure is not a thing you need worry about.
The throttle posistion is the next thing to be adjusted.You cannot do this yourself,it needs a set of protractor guages to set the throttle and MFI possitions accurately.You will have to contact a Mercedes club member near you to find a specialist who has the gear.if you don't do it.two things will destroy your engine,one is too rich running and the other, too lean running.[