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1990 300E
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745 Posts
Discussion Starter #1
Gents,

I'm not sure what's going on here and could use some wisdom. It all started with randomly not starting unless I move the shifter P to N or P to R then back to P. So I changed the NSS with an OEM unit and still had the same issue. Thinking that the NSS might've been defective, I got a second OEM NSS unit and it still does it.

i didn't see any way to adjust the NSS unless I'm missing something. Any inputs are appreciated.

Thank you.
 

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W124
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4,898 Posts
The switch IS adjustable within a slot but granted it doesn't allow much motion. The adjustment is primarily to allow a full detent into park with no restriction caused by the switch. One way to test around the NSS is to introduce 12v to the center pin of the three pin connector up by the brake booster under the bonnet. BE SURE YOU HAVE THE CAR IN NEUTRAL - because the engine will start in gear with this work around.
 

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95" W124/ E220 MasterPiece and 01" W210/ E200 KOMPRESSER
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245 Posts
I am thinking about that your ignition tumbler might be the culprit since you change your second NSS.

The tumbler transfers the signal and links your positive power to the pin 2 as Tuttebenne mentioned above.
If your PIN 2 trial works successfully, that means your problem is upstream.

The other upstream problem would be the ATT relay behind the instrument cluster.
If the key tumbler fails or partially fails, this relay cannot connect the circuit thus preventing your car to start.
Good luck.
 

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1990 300E
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745 Posts
Discussion Starter #4
I am thinking about that your ignition tumbler might be the culprit since you change your second NSS.

The tumbler transfers the signal and links your positive power to the pin 2 as Tuttebenne mentioned above.
If your PIN 2 trial works successfully, that means your problem is upstream.

The other upstream problem would be the ATT relay behind the instrument cluster.
If the key tumbler fails or partially fails, this relay cannot connect the circuit thus preventing your car to start.
Good luck.
Hmm, I haven't thought of this angle before. Here's what's happening in my case: with my right hand I keep the ignition key on IGN mode, with the left hand I move the shifter from P - N and then the engine starts. So, it sounds to me like the 12vdc is going through the ignition switch and then gets stuck at NSS until the contacts are made inside of NSS by fiddling with the shifter. As soon as the contacts are made inside of NSS, power then goes to the starting solenoid.

Is my logic sound?
 

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W124
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Hmm, I haven't thought of this angle before. Here's what's happening in my case: with my right hand I keep the ignition key on IGN mode, with the left hand I move the shifter from P - N and then the engine starts. So, it sounds to me like the 12vdc is going through the ignition switch and then gets stuck at NSS until the contacts are made inside of NSS by fiddling with the shifter. As soon as the contacts are made inside of NSS, power then goes to the starting solenoid.

Is my logic sound?
Your logic seems sound to me. THe problem is it doesn't fix the problem :) There are two things to do:
- check to ensure both plastic bushings are in perfect condition on the NSS end and on the shifter end of the rod that connects them. Lost motion due to shot bushings can prevent full P engagement.
- once the above has been verified/resolved, use an ohm meter to check for continuity at the NSS in neutral and in Park. (on the car with nuetral and Park selected by the shifter, not from underneath the car.

Let us know how you make out.
 

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95" W124/ E220 MasterPiece and 01" W210/ E200 KOMPRESSER
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You could just simply plugin the new NSS (or the one you just remove from the car) with its cable without installing it.
There is a pinhole which you could align the NSS into Neutral position, whereas this position is ok for starting your engine.
Then you could test out your NSS.

If all goes fine...then all you need to do is to adjust your connecting rod/NSS or both cause it is not resting on the correct position.
Good luck.
 

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W124
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The elephant in the room is the condition of your starter. A bad solenoid will give the exact same symptoms you describe at the beginning of the thread. Your jostling the engine by moving the shifter back and forth could be causing the worn solenoid connections to momentarily have continuity and start the car only to fail again later. Next time this happens, have an assistant sit in the car with the key in the full clockwise position as if starting the car. Make sure the shifter is in Park. At this point you can do two things:
1. measure the voltage at the small wire on the solenoid. (it should be around 12 volts)
2. if there is voltage there, you have a bad solenoid. You could prove it by smacking it while your assistant has the key in the "start" position. BEWARE: THE STARTER WILL PROBABLY ENGAGE AND THE ENGINE WILL TRY TO START SO WATCH WHERE YOU HAVE YOU HANDS PLACED WHEN YOU DO THIS.
 

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1990 300E
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Discussion Starter #10
Thanks to all for the helpful inputs. Some more info:

- starter was rebuilt before the NSS (s) was purchased.
- plastic bushing on the shifter replaced few years ago.
- I tried adjusting the rod but didn't adjust the actual NSS, still the same problem.
- yes, reverse lights are working ok. Good call though!

Haven't been driving the car as of late due to snow/ice in my hood but hoping to jack it up this evening and play with the NSS adjustments. I'm hoping to drive the car again starting tomorrow. I have my daughter this week so that's a huge help when I'm under the car!

I'll update this thread once I have done more work per your suggestions.
 

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1990 300E
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Discussion Starter #11
I FINALLY resolved this issue with a third NSS which is also an OEM unit. As you can see from the pics, both units "seem" to be the same but obviously, they aren't. The third unit worked right from the get go and I'm now able to start in Park, like normal people!

Maybe when I'm snowed in one day and have nothing better to do, I'll take apart the non functioning unit and see what's up with it. it's only four pins, should be easy to figure out. For now, this case is closed and thank you for your assist.

2619203


2619204
 

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W124
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I drilled out the rivets on one and repaired the switch. A couple of new pop rivets and its now on the shelf for an emergency.

PS: Glad you solved the problem!
 

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1995 E320 Cabriolet
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55 Posts
Just
Gents,

I'm not sure what's going on here and could use some wisdom. It all started with randomly not starting unless I move the shifter P to N or P to R then back to P. So I changed the NSS with an OEM unit and still had the same issue. Thinking that the NSS might've been defective, I got a second OEM NSS unit and it still does it.

i didn't see any way to adjust the NSS unless I'm missing something. Any inputs are appreciated.

Thank you.
replaced a second NSS in my 1995 E320. Never replaced a single one in any other vehicle I’ve ever owned, some with much higher mileage
Thanks to all for the helpful inputs. Some more info:

  • starter was rebuilt before the NSS (s) was purchased.
  • plastic bushing on the shifter replaced few years ago.
  • I tried adjusting the rod but didn't adjust the actual NSS, still the same problem.
  • yes, reverse lights are working ok. Good call though!
Haven't been driving the car as of late due to snow/ice in my hood but hoping to jack it up this evening and play with the NSS adjustments. I'm hoping to drive the car again starting tomorrow. I have my daughter this week so that's a huge help when I'm under the car!

I'll update this thread once I have done more work per your suggestions.
Just replaced a second NSS in my 95 e320. Never had to replace one in any other vehicle I’ve owned, some with much higher mileage
 

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1990 300E
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745 Posts
Discussion Starter #16
Did you check the brake light switch ?
No I didn't, should I have? The brake lights come on normally when I step on the brake but is there something else to consider?
 

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1990 300E
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Discussion Starter #18
Awesome, thank you.
 
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