The system is D-jet. The "D" stands for druck, pressure in German. The system is basically the same as used on the earliest V8s. There will be trigger points in the base of the distributor that fire injectors in groups of three. Volvo 164e had similar system and maybe the same points. There also was a BMW that used the system (also very rare). The Volvo is the common 6cyl version, although if you need trigger points the four cyl versions used in VW, Volvo, and 914 Porsche 1.7 and 2.0l may be a fit.

Since you refered to the battery a good place to start is the positive battery cable. In all the MB versions the main power lead was attached to the positive lead. The wire was not incorporated into the cars wiring harness and if you follow it, it will lead you to the EFI relay (controller relay). Once powered up the fuel pump ran for 1 sec and died unless the car was cranked.

The injectors are feed side controlled unlike modern injectors that are controlled on the ground side. A most usefull characteristic is the operation of the acceleration enrichment system built into thye throttle switch. If you turn the car on with the engine off and move the throttle to full throttle slowly you will hear the group of injectors, currently engaged by the trigger points, fire twenty times. This is always the first step to see if the controller is functioning. It also can be used to verify the trigger points, somewhat.

The points often get stiff with time and don't close fast enough to reopen the next go round. Sort of like floating valves.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician