Your R checks mean nothing b/c NSS does not just intigrate the starter circuit..it also feeds Ea , ASR , TNNsignal, etc...so , until you isolate every one of those circuits , you can not check the starter circuit.
So , we go in the sequece chain as I posted...

If you are getting power to x27 and no starter, but you get starter with x27 bat jumper. then you do not have sufficient power at x27 from the logic chain [ ign/sw/nss/k38/etc] ...to trigger the starter soinoid...ie, a poor connection in that feed ... Power to X27 has to be the SAME as Bat voltage or someting is bad....that is why we jumper each link in that chain..
to find which one is the culprit....somewhere in that chain is a voltage open or drop....your ohms readings are not needed on this application.I will see if I can post the schematic for starter circuit and then it will be very plain to see this series circuit.
I know it is hard for you to visualize , as it is hard for me to read the schematic and have you come at me with physical wire discriptions and questions.

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A Dalton

thanks for all the help.
I didn't know if the resistance readings were a clue. Will wait to hear from you on what to try next.

What to try next has been posted back in post #41.
You have to get to the K38 relay and jumper as described in that post.

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A Dalton

I just wanted to take the time to say thank you Dalton. I experienced a no start/no crank situation with my 1995 mercedes E320 wagon, and I spent quite a bit of time trying to track down diagnostic information & wiring diagrams without much luck. I found a few posts that referenced a few things here or there, but none of them took the time to describe the circuit in detail. Your posts made the entire process perfectly clear. I now understand the path of the circuit from the battery all the way to the starter; the location and appearance of the ignition, K38, X49, K27, and starter sections of the circuit; how to properly jumper these locations if it is necessary to bypass them; and the really handy K27 "emergency" start trick. With your post I can finally diagnose & fix my car...that is once it stops being a pain in the butt by deciding to work again. I know that it will break again sometime soon, and until I can afford a new digital multimeter I don't have the ability to test beyond On/Off with my test light. I also wanted to tell you...not sure how to put this, but you have great patience with dealing with others. I know that electronics can be a pain to deal with, but it definitely helps to follow the procedure...and the path of the circuit...and I suppose to understand basic circuitry. Thank you again very much!

You're Welcome .

A Dalton
BenzTechs

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A Dalton

thanks AD. I will read thru the forum to try and figure out how to pull the cluster.

Did any body mention posible faulty ignition switch? I didnt read all the the pages. I would take the switch out with a paper clip and turn it with a screw driver to see if you get power to the starter.

Yes , we did... the ign sw is in the feed circuit we are checking now.

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A Dalton

morning update. I listed this as a new thread in case someone has had a similar situation with arming the ata.

I am running through diagnostics with the very patient help of A. Dalton. We have covered testing fuses, battery, x27 x49 and are up to pulling the instrument cluster to check k38.
Before I did that I wanted to post what i discovered this morning about the ATA system in hopes that someone my have experience that would help me.
The ATA led would not arm from the driver's side door. Today i discovered that it will arm (start flashing on the dash) from the rear hatch and from the passenger side door. The drivers side door will not disarm the alarm. IE if i unlock the driver door and open the alarms go off. However if i then close the door and lock it the alarm is disabled. Both the passenger door and hatch will arm and disarm the system. I tried cranking each time between arming and disarming by various doors but still no crank. At least I know the ATA led is powered now.

To be darn sure, I took the battery for testing and sure enough... it failed the test generating 580cca and 12.7 volts. Seems kinda borderline but at least it was the correct battery (by interstate book) and i ordered a new one for late today or tomorrow. That will go in and i will post results.

A Dalton, Hope you're still willing to help.
I installed new battery and pulled the instrument cluster when the tools arrived today. (not as hard as I thought). I pulled free the round connector with 15 wires behind the fuel gage. I am assuming this is the k38. The pins are arranged in a circle. I jumped 1 & 3 (on the harness connector not on the pins protruding from the cluster). No start. I checked for voltage on both positions in the crank position and got zero. any help appreciated.

You just pull the relay. It should be towards the upper/left of the dash opening. [ behind the gas gauge location] There may be some insulation in front of it.

Look for a small , regular looking relay. Pull it and jumper 30 and 87 ..plug it back in and try to start the car.............................

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A Dalton

Thanks. I will get on it first thing in the morning.

Found the relay just where you described.
soldered across 30 and 87 and plugged in.
on crank position the horn blows steady but no start.

Make sure the alarm is not armed
All doors closed and hood closed.

Is horn steady, or is it repeating on/off ...like alarm mode?

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A Dalton