Replaced engine wiring harness, now no tachometer!
 

I replaced the harness on my 89 300E with one from a donor car. The new harness is in a lot better shape than mine was, especially the pin connectors in the CIS-E plug. Soldered the wires carefully but hit a snag. The black wire with the yellow stripe that comes from the EZL plug is somewhere up in the harness. I spliced the old one back in. There are two green/yellow stripe wires from the terminal on the EZL instead of the one in my old harness. I don't think that's a problem either. Problem is I have no tach or temp gauge. Engine started up and runs fine. ABS light is on but I'm sure that's the OVP doing that. Lambda cycles from 46 to 48% so that looks good. I have two additional small brown ground wires in the repl harness so I grounded them but still didn't make the instruments work.

Got the tach working. There was a short in the fuel pump relay. But still no temp gauge, and I just noticed that the A/C compressor clutch isn't engaging. Further tests reveal no current to the EHA. I guess I'm destined to spend hours and hours in the dungen of confusing PDF files known as the Model W124 Service Manual Library!

The latest. I removed the sheathing from the harness and found that the black/yellow stripe wire was factory spliced into a solid green wire. :confused: Once I matched those up the temp gauge is working. Still have to figure out the A/C compressor though. Intermittant stalling is still there though, so I haven't made any headway into the real problem. There are no components left to replace in this thing. OVP, fuel pump relay, O2 sensor, temp sensor, CISE computer, fuel distributor w/airflow meter, injectors, fuel pumps, fuel pressure regulator and now the harness itself. Look for a new thread about a Ford engine swap into W124 soon.