82 300TD No Start After Long Drive

[montuckyride]

Dear Forum: My 1982 300td would not start after an hour long drive. I couldn’t hear the starter engage at all. The glow plug light turned on. For forty-five minutes I whacked the starter (new was replaced one month ago). I shifted the gear shifter from park to neutral and wiggled it around, while trying to start the car. The NSS was replaced two months ago. I bought a new one from Mercedes Benz and had it replaced at a Mercedes dealership. The AAA tow-truck man took the voltage of the battery and said it was a little low but was around 12 volts. He said he could not hear the solenoid click, but it was hard to hear with his tow truck running. I towed my wagon back to town, and as soon as it got off the tow truck bed it started up. I made an appointment with the mechanic who installed my latest starter and he doesn’t know why it didn’t start on the highway. He said the ignition which should not have warmed up on the highway. He said that he checked the voltage going to the NSS switch and it was normal. The starter and solenoid is rebuilt and the mechanic has guaranteed it, and if it does not work he has said he will replace it for free. The car has started perfectly every time since three weeks ago when I got stuck sixty miles out of town. My insurance covered the towing expense, and I have the basic triple AAA, but I am basically afraid to drive my car out of town. I’ve owned my wagon for five years and have driven about 50,000 miles in it, and driven multiple times across country. Every time I’ve been out of town in the middle of nowhere and the car wouldn’t start, I’ve gotten it jump started, or whacked the starter or played around with the shifter. But now I’ve replaced the NSS and starter in the past two months and I am still getting stuck. I really like my car for long drives and trips, so it really bothers me that I don’t trust my car enough to start when I need to get gas or a cup of coffee.
I’ve had two mechanics tell me that it is nearly impossible to diagnosis what’s wrong when my car is starting. Maybe what I should do is drive thirty miles out of town and then thirty miles back to the mechanic, then park outside his shop and see if the car starts. The tow truck mechanic said one of my headlights looked dim. I read another post about this, could a bad ground connection have somehow played a part in this? I think I may buy a remote starter and stick it in the glove box, then if my car won’t start I can see if the starter is working or not, then I can determine if the problem is the ignition switch or the NSS.

Maybe the ignition switch wiring is dirty? But why would driving on the highway cause the ignition switch to fail, and then my car starts perfectly every time around town since? I’ve taken the instrument cluster out two or three times in the past and once I didn’t tighten the oil pressure gauge correctly and I had oil leak out of the driver side kick panel. Maybe that oil leak has contaminated the ignition switch?
I will clean the battery connections and the ground connection with my brush.
My key turns easily in the ignition tumbler. And the key springs back. I don’t think the wheel was locked when I got stuck a few weeks ago.
Please let me know if you guys have any thoughts or ideas on what might be the problem. Thanks- Andrew