A question about keys and ignition switch. 450sel content

I pulled the Mercedes out yesterday and it fired right up, then shut right down. 
I noticed when I took my hand off the key in the cranking position, all the gauges dropped to zero. 
if I keep a little pressure on the key after start it's fine. I imagine the first bump in the road could shut it off. 
seems simple but I have never experienced this before. Can I take the switch apart and re-index it somehow?  
It's like the entire assembly needs to rotate counter clockwise a touch...or if there are positive detents in the switch, maybe they are worn?

Europeans generally have a switch screwed to the back of the ignition lock.  No idea on Mercs, but Volvos of the 70s and 80s often needed you to turn the switch back a bit for the accessories to turn on.  New switch would fix it.

It may also be a dead spot in the contacts.  If the switch can be disassembled, you can fix it with some careful sandpapering or Scotchbrite work.

Well, the first step has me stalled. 
well, technically the second step. I was able remove the trim ring. Sigh. 
According to the manual, I should turn the key to the acc position and insert a 1.25mm wire into the passage, releasing the barrel. 

Do you need to remove the tumbler?  FCP Eurpo has a pretty good breakdown.

However, I don't have the little key way. At least...I don't see it. I took an .040 Allen wrench and poked around to no avail. The smallest probe I have is .035 or so and I tried sliding that between the plastic and the barrel, and that is too big. 
Maybe this is an aftermarket piece that unlocks in some other mysterious way?

Streetwiseguy said:

Do you need to remove the tumbler?  Is there a switch screwed to the back of it?

Could be...I was trying to avoid taking the dash apart since it appears Mr Benz intended this to all come out the front. 

The FCP Euro image looks like the switch is held in by at least one screw from the other side, assuming it is of your vehicle.

I also posted on the w116 forum...any info gained will be shared. 

The 116 forum is fairly inactive...so while I am waiting...

I found that the plastic cover that screws off on a 6.9 just pops off. 

Though for sure I would find a clue behind there, but not so far. All the jiggling in the world hasn't made a difference either. 

it does say Huf on the plastic cover and on the key. It seems that corresponds with original equipment. I'm now search for any info on this type of switch used in a Mercedes'. So far, everything shows the access port to be unlocked with a .050 tool (or a paper clip)

I would not attempt to remove it unless the key is IN. 

Try it again but place the key in the tumbler and see if it comes out. Otherwise all they little keys or whatever they are called will fall out. 

Slippery said:

I would not attempt to remove it unless the key is IN. 

Try it again but place the key in the tumbler and see if it comes out. Otherwise all they little keys or whatever they are called will fall out. 

Thank you...all my jiggling has been with the key.  I know this is something simple and it is passing me by. 
I thought with the snap ring off the whole shooting match would slide out....

Looking at the pictures again, your locking ring is holding the cover plate between the outside and the ignition where the key fits. Looks like that might be a cover, see there is grease oozing out. 

I would put the key in and carefully try to pry that cover with a very small flathead screwdriver

In reply to Slippery :

Yeah....I sort of tried that but probably need to go in with more verve. Stand by. 

Nothing yet...here is a close up. I have made a few marks on the edge of the casing but it looks like someone has been here before. 

What are you hoping to get at?  Does the lock turn?  If so, you are attacking from the wrong end.  The tumbler goes into a steering lock mechanism that is attached to the steering column with anti theft bolts.  You are not going to find anything electrical in there.

Really.

Is this an arrow here where I placed the circle? Or a blemish?

I cant now, but I will spend some time researching tomorrow. 

This car is probably closer to a w114/w115 than a w123. So maybe the answer is found checking those cars. Even an R107 could use the same ignition. 

Streetwiseguy said:

What are you hoping to get at?  Does the lock turn?  If so, you are attacking from the wrong end.  The tumbler goes into a steering lock mechanism that is attached to the steering column with anti theft bolts.  You are not going to find anything electrical in there.

Really.

So...what is happening is the car starts...but the car will shut off with the slightest counter clockwise shift of the key position. So I THINK , the contacts have either shifted or something is wonky with the contacts themselves, so i thought I would take the cylinder out to examine. 
Unfortunately, that's where I'm stuck. 
I will do some more research as well...I really do think I'm missing something obvious. I appreciate the help. 
 

In reply to Slippery :

That appears to be a blemish in real life. 

Woke up early with this on my brain. 
I went out...continued to look for clues...I started the car for the heck of it and it stayed running. I shot a little WD into the keyhole and it seemed to get better. 
turned the car on and off several times and it is absolutely not shutting off so easily (like from vibration). 
maybe it was inactivity?

I am going to talk to a MB service friend today and see if he can shed any light on this, but I think MAYBE the problem was from dormancy. I haven't run the car in a while. 

I am cautiously optimistic. 

Hopefully working the lock gets it going.  The only time I cursed at my GTV-6 was similar to what is happening to you.  I drove the car to Drill, about an hour form my house.  We get released to go home on Sunday, get in start the car but when I let go of the key it shut off.  Tried it a few time with the same result.  I found that if I held the key in just the right spot it would stay running so I drive home holding the key in place with one hand and shifting, steering and everything else with the other.  Good times.

This type problem often occurs when the switch wears where the lock enters it. I echo what Streetwise said, you are attacking from the wrong end. You need to go from the back side of the steering lock assembly and remove the electric switch from the back of the lock. This will be two pretty obvious small Phillips screws. See the posted picture above from the FCP site. Also many of the interior trim panels on theese cars are "pull off" components. Easily damaged now that they are old cars. You won't find hardware