Hello,
I am fairly new to the forum.

I am puzzled by a no start problem on a 1990 300TE. Here is a summary of what I've done:

1. car eventually did not start in either P or N. removed starter and had it checked. it was bad so I put a new one in. still nothing. engine does not even turn nor solenoid clicks.

2. did test on X27 connector near brake booster. applied direct voltage to center pin on connector (not plug) and car started right up. this means I hooked up starter corectly.

3. noticed bushing gone at rod-NSS bracket, so I put a new one. still nothing.

4. did test on X27 plug this time. hooked up light to center and grounded other end. while holding key on "start" position, the light comes on at Park and at Neutral, and not at other gears. this means NSS is OK, right?

so what next? the car still does not even crank.

for the time being, I can "jump" it be applying 12v on X27, but wife can't do that.

Any help is greatly appreciated.
Claudio

You have to test x27 center pin [ vi/w] with test lamp while connector is plugged in so that the circuit has a LOAD on it.
If the test lamp goes out with the load on it , the suspect is bad contacts in NSS or Ignition sw.
You can have a 12v test lamp verify 12v at pin from NSS or Ign. sw. , but it will drop out as soon as the starter sol load is applied.
You know the circuit is good from x27 downstream b/c you can jumper starter circuit from x27 with 12 v bat supply..............................
A trick I use is to hold the Ign sw in the start position with left hand while moving the shift lever back and forth at N or P ...if starter kicks in, NSS is suspect.

Arthur,
Thanks for your input. If I understood correctly, I should test X27 connected and see if I still get a light in P or N while the load is applied, right? I will do that tomorrow since it is dark now.

If no light, means bad contacts on NSS or switch itself? or it could also be the ignition switch? From reading past threads, NSS is a common cause for no start conditions.

And if I do get lights? well, it should start, right?

I am not clear on the next test on X49/2 I saw on other posts. I do not have a K38 relay behind cluster. That is after 93 models as I understand.

I will report back tomorrow. Thanks again.

Correct.....
No K38 Interlock relay on your 124.090 chassis.
Power chain is Bat + > ign sw > NSS > X27...

So, diagnosis is NSS OR Ign sw dropping out from load.... you have 12 v lamp test b/c there is no load on the contacts............do the ign sw hold test I posted.

A expected, when I tested X27 with a load, no lights were present in either P nor N.

So is this enough to say it is either a faulty NSS or ignition switch? Any way of determining which one it is? The NSS is much easier to change.

The dealer closes at 1pm today. I will put all my chips on the NSS and go from there. It seems to be the most common culprit.

Did you do the ign sw hold test I posted?????????????????

I am trying to find it....

trying to find what ???

The past post. I think I remember seeing it. Is it wiggling the key while in start position? If so, I've done that and nothing.

Isn't it post #2? The load test?

__________________

1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

The last line/tip in the very first post I listed ..post #2
You hold the key with left hand over to the START POSITION and fool with the gear selector..that will give us an indication of NSS contacts.

..or , you just jumper pins 3 and 4 at X49/2.. that is NSS feed for circuit 50. [ vi and vi/wt wires].......

key in start position and held there. moved selector from P to N and back and nothing.
on my way to jumper X49 and see if that does it. will report back in a few minutes.

it started !!! after jumpering X49/2 the two wires violet and violet/white.
so this means bad contacts on NSS, right?

Correct...............

Thank you Arthur for your assistance and especially your patience. On my way to the dealer for the NSS. Will post results later and pics of the broken NSS if it is so internally.