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W111 250se coupe : starting problem

3604 Views 4 Replies 2 Participants Last post by  FiLNguyen
Hey all, I recently aquired a 1967 w111 250se coupe from NewYork and had it shipped over to California.

Car started and was running fine, one day I went to start the car and it didn't even want to turn over. No clicking sound or anything. First thing I did was swap out a good battery, all new fuses, wiggle key ignition back and forth, and floor shifter/neutral. All with no luck of starting the car.

Put the car on jackstands so I can get under and take a look at the starter. Gave the solenoid a good couple thump, maybe my starter was on its way out but still nothing.

But I did notice two wires (one big one small) from the starter to a terminal screw box, on the frame. which I believe goes to the alternator, melted together due to it being so close to the manifold (my best guess) I replaced it with new wires of similar size. Also noticed the main 0 gauge wire from the battery to the starter was chaffing on the oil pan if I remember correctly and was making contacting, I patched up that wire (will eventually replace once I figure out my main problem.)

After all that the car still wont turn over, and all fuses from the main fuse box still looks fine.

I tested the starter by jumping the small wire from the starter directly to the battery. You can clearly hear the starter engaging. So the next thing I did was turn the key to #2 and and did the same thing, the car started up instantly. Yes, I understand that I shouldn't have done that as I could ruin the starter, but I only did it once and removed the wire from the battery the moment the car started.

This is as far as I got with trying to figure out why my car all of a sudden won't start.

What I want to know is, by jumping the wire from starter to battery which bypasses the ignition and neutral safety switch. Does that mean both my ignition and neutral safety switch is in proper working condition?

I plan on working on the car tomorrow to see if I can trace any further bad wIre and what not.

If anyone can help/guide me to figuring out this problem it would be greatly appreciated. I'm open ears to anything.

And for the record I did try using the search button... This wasn't a problem that happened just yesterday. My car has been sitting on jack stands for probably a month now while I try and figure out this problem every chance I get to work on the car.

Thank you ahead of time.
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Thank you for the input and suggestion, I will to some research on the safety switch and see if Can find out how to bypass / test / adjust it. Luckily I just purchased a service manual, maybe I can find more info on that.

If you can think of anything else I should do or doing wrong please let me know.

Thanks again
So I got under the car and for some reason cannot locate the neutral safety switch. Maybe I'm blind or something but did my model not come with them?

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I was able to diagnosis the problem and fix it. Going to post up what I found, just in case anyone else runs into this problem.

After chasing wires for the past two days and testing voltage from the starter all the way to the ignition.

My ignition switch was giving power but not to terminal 50 which powers the starter solenoid (small wire on the solenoid) part was $200+ for a new one but luckily I had a 67 w108 parts car so pulled it from there is installed it in the coupe and fixed my starting issue.

From the ignition switch terminal 50 there is a violet/white wire that goes to the NSS (neutral safety switch / inhibitor switch / starter lock) which is located under the hood / bonnet on the left side of the firewall. With the key turned to #2 and in park or neutral, it makes a connection and sends power to a solid violet wire which runs along the firewall to the right side and down to a terminal box below the alternator / generator. From the terminal box it goes to the starter solenoid.

I am not familiar at all with these older classic motors but I have learned quite bit the past couple days.

If you want to test you NSS to see if whether the switch is bad or if it's the ignition. Just unplug the harness that is attached to the NSS and jump the violet / white wire to the violet wire. Try and start the car. If the car starts then your NSS is bad, If car doesn't start then run a multimeter to the purple / white wire and see if you're getting any reading.

Hope this helps others.
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