So... i replaced ignition switch, start lockout relay (couldnt hear or feel click so replaced now i can feel it click when i turn the key. Replaced overvoltage protection relay with genuine mercedes because it was offbrand and suspect. Tested continuity at harness leading to trans park safety relay and get continuity in park or neutral not in any other position so feel that is good. Can start car by shorting x27 under hood drivers side pin 2 (violet white) to battery pos starter will turn and if key is on, starts and runs/drives fine... what am i missing?

Weird thing is i get like 10v on that pin with ignition on, is this normal? I know from looking at schematics that this circuit is also tied to fuel pumps but thought it was odd to see any voltage whatsoever unless in start position.

I'm running into a brick wall, can't think of anything else to try and not as familiar as i should be with these things for the level of troubleshooting this is requiring.

Some things will help folks to help you:
Country the car is associated with; USA, European, etc.
Year model of car.
Engine type.
Decode "X27"; Mother Benz uses "X" for different purposes.
A starter circuit diagram.

Don't have diagram in easy upload form, specific model is 1994 E320 US version. M104 Engine. I think it's even the California version at that (after getting manuals there are a couple things marked Cali model only that it has). I finally figured it out while going over it again and again in my mind and on the car. Finally I got over my mental block of already replaced the starter switch and started over with Troubleshooting 101. Pulled starter switch assembly back out, shorted pin 30 to pin 50 with the starter lockout relay bypassed as well and got starter movement. So I bench tested my brand new switch and it didn't work. I disassembled it and benched it without the assembly and it worked so I scratched my head much and really took time looking at the way it went together and I guess I had gotten it put together clocked a little bit wrong which I thought was impossible... That or i cleaned the crap outta the contacts with a wire brush from my gun cleaning kit and the connector with another bore cleaning brush from same kit and put it all back together and it fired right up. Unbypassed the starter lockout relay and still good.

Long story short, never assume and test each assembly before install for proper operation before you go through the trouble of installing in vehicle.

On another side note that may help someone out, I got excited and put most of it back together after the first time taking switch out and had clocked the assembly just slightly cocked and while it would go back together that way, the little rubber boot that goes over the cylinder housing as a last trim piece looked like it was cockeyed so when you put it in and before you tighten the bolt on the clamp ring that hold it all in (besides the retaining pin) make sure you twist it to where the retaining pin is in the middle of it's hole, that seemed to do the trick it's only a couple degrees of play but just enough to notice when it's all back together. Hope it helps someone. I got the schematic from this forum that started me out till my repair manuals got here. I love that there are other Benz enthusiasts out there willing to help us keep as many of these wonderfully engineered cars on the road as possible.

X27 is the 3 prong connector that links the wire coming from behind dash to the wiring going to starter solenoid and a couple other sensors. The Violet/white is the starter solenoid so it's a way easier way to test if starter works than to climb under car and short battery+ to it there. Also how I've been starting the car when I need to move it since this has happened. I use a mechanic's "remote start switch" which is basically a length of wire (probably 18guage, maybe 16) with alligator clips on each end and a trigger or push button momentary switch in the middle. hook one side to battery+ and the other to starter solenoid or in my shortcut case, the wire going directly to it, and presto, you bypass all the circuitry from the key to the solenoid. If you turn the key on first to fire up the ignition circuits and fuel pumps, etc, then it should start and run which usually rules out a bunch of possibilities as they usually would otherwise affect those systems as well.

When you turn the Ignition on to start are you actually getting voltage where the wire from the Ignition switch connects to the Starter solenoid? And, when you do that with the volt meter you can verify what voltage you are getting.

I know you feel you covered that at the connector but that is not exactly the same.

It might be that you actually have to remove the wire from the from the ignition switch to the solenoid to be sure it is making good contact with the solenoid terminal. Since the alligator clips may be making a different contact.

If you are only hearing the click from inside of the Car it is possible you are hearing something else click. Have someone turn the key while you listen with the hood open so you can hear exactly where the sound comes from.

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84 300D, 82 Volvo 244Gl Diesel