Ignition key does not work all the time - PeachParts Mercedes-Benz Forum

admanles · #1 11-10-2004, 11:31 AM

Hi all, new to the forum, but from what I can see... it's a great one. I just inherited a 1980 300sd. The problem is in trying to start the car. I'm able to turn the key maybe a quarter turn in the ignition, I think right before the glow plug light would come on and it sticks, like there is something metal blocking the key from turning from that point on. I'll jiggle the key back and forth, move the steering wheel, remove the key a few times, say a few choice words, and eventually with a "click" the key would turn, and I'm able to start the car... It'll start fine a few times after that,... then it will happen again. It does it with both keys. Any ideas anyone as to what it might be? The only other problems so far, is the tach not working, which I remember a thread about that here somewhere, the left rear passanger lock not locking automatically (another thread I found) and the car being gutless, which from another thread might be a vacuum hose from/to the turbo? got to re-read that one... but you guys are great, lots of useful information. I'm hoping you can point me in the right direction on this ignition thing.

Thanks in advance

Les

#2 11-10-2004, 11:39 AM

You want to buy a replacement ignition tumbler from a dealer and either have it installed or install it yourself. Yours is worn out, and I'm told that if it becomes so worn out that your key gets stuck in there or it won't turn at all anymore, it has to be drilled out, which is a pain in the you know where. You'll need the car's title or registration as well as your drivers' license to order this part, if your dealer is like my dealer.

JamesStein · #3 11-10-2004, 12:09 PM

Before you buy the tumbler I would remove the one you have. My wifes 300D had a similar problem and it was not the tumbler but part of the ignition assembly.

Take a look at this page I am working on..

http://garnet.acns.fsu.edu/~jjs5772/W123

SD Blue · #4 11-10-2004, 01:01 PM

Before you start tearing things apart, have you tried lubrication?

Be sure and use only lock/key lube only. I have been told that anything else may cause even more problems internally. Maybe even resulting in the ignition needing drilled $$$.

whunter · #5 11-10-2004, 01:11 PM

If not, take it to the Stealership NOW.

When it stops working the repair time and cost will be higher.

Is this your only car?
DIY is cheaper on money, but will take more of your time.

JamesStein · #6 11-10-2004, 01:45 PM

I agree with whunter. If you don't feel comfortable working on it yourself take it in to get looked at now. If it seizes it gets very expensive.

I would seriously think about removing the tumbler, its easy to do, and check to see if its binding in any way at all. I would do that before I even thought about ordering a new one. Lubricating the tumbler with a graphite powder is a good idea. But I don't think it will help your situation. It really sounds like you have a failure in the internal mechanism of the assembly.

admanles · #7 11-10-2004, 02:15 PM

Thanks all for your responses! Is the tumbler easy to remove? I do have time on my side as my primary vehicle is an 03 Expedition. This car has a lot of sentimental value to me. I had just stared working for my dad and was there when he bought it. And have vivid memories of him handing over the check. I've got the pink slip so I assume I should have no problems getting the parts. I'm fairly handy with tools, so is this something some one with medium skills can handle? Also what service manual do you suggest I get?

Again thanks all for your responses.... This is a great group!

Les

admanles · #8 11-10-2004, 02:21 PM

What a great site James. I should have looked at your site before posting my question.

Thanks!

Les

KCampbell · #9 11-10-2004, 02:28 PM

I have been quite happy with the service manual on CD, I was able to purchase a "totally legitimate copy" on eBay for $11.

The CD is basically the paper manual scanned into PDFs. The images didn't come through very well, but it's very comprehensive and I have found it helpful.

Kevin

#10 11-10-2004, 02:38 PM

the problem to some extent on all three of my W123s. Sometimes problem will go away for months and then come back without warning. Is there a can of something I can pour in my fuel tank that will fix it while I drive? I LOVE that.

tomm9298 · #11 11-10-2004, 05:26 PM

I have a fairly new key and lock, less than 2 years old. Sometimes when I turn the key to pre-glow detent, it will turn no further. This is after the glo light goes out. This happens about once a month. Will try the lock lube and see if it goes away.

admanles · #12 11-10-2004, 06:06 PM

Thanks again for all your responses. I decided to take the easy route and took it in to a friend that works on Mercedes & BMWs. I should be getting it back in an hour and $130 lighter in my wallet. The price of impatience.

Les

#13 11-15-2004, 09:45 AM

the plugs have glow-cycled once is some kind of safety device built into the system, to possibly prevent you from starting the car after the pre-glow has gone "cold"...maybe to prevent "flooding" or some other interruption of the sequence...until you start over again. This happens to me ever so often, and it has the "feel" of a protective device rather than a malfunction.

tomm9298 · #14 11-15-2004, 11:04 AM

was thinking. It did it yesterday again. Turned off key and recycled, worked fine. Maybe due to cold temps. Maybe it's Hilda's way of saying, "I want new glow plugs!!"????

JamesStein · #15 11-15-2004, 11:38 AM

Quote:

Originally Posted by Jim B+

the plugs have glow-cycled once is some kind of safety device built into the system, to possibly prevent you from starting the car after the pre-glow has gone "cold"...maybe to prevent "flooding" or some other interruption of the sequence...until you start over again. This happens to me ever so often, and it has the "feel" of a protective device rather than a malfunction.

You are correct, its by design. But I doubt it has anything to do with the glowplugs since the ingition is the same in both the diesels and the gassers. I would wager that its to prevent you from engaging the starter if your engine is already running.

If you were to take apart the ignition switch (the electrical portion) and look at the housing that it sits in you'd see a series of groves. Oddly, dispite the large amount of pictures I've taken of the guts of one of these things, I don't have one of that. Perhaps I'll take one when I get back home. In this picture of the actual mechanism inside the switch you can see a lever with a pin on the end. That pin rides in the groove in the housing and causes the lever to be moved out when you turn the key into the 'start' position or actually just a hair past the 'glow' position. That lever then blocks the ignition from going back into the start position.