Cannot insert key in ignition! (W123) - PeachParts Mercedes-Benz Forum

mfripp · #1 02-10-2008, 09:14 PM

I have a 1981 Mercedes 300D, which I've owned for about 3 1/2 years. I've never had any problem with the ignition lock, but suddenly today I found I can't insert the key into it. It goes in about 1/4" and then something blocks it.

I poked around inside the keyhole, and it looks like there are two moving pieces of metal just inside the key slot -- one on the left/bottom side, and one on the right/top side. The one on the left sits nicely out of the way. But the one on the right seems to have come loose. I can see a worn, straight edge, which looks like it's where the key normally moves past it. Then, further in, I see a semi-circular edge, which is blocking the key from going down further, into the pin mechanism. I can push this piece of metal around with screwdrivers and wire, and even get one corner of it to almost protrude from the key slot. i.e., it seems to be floating around freely in there, as much as the space and its shape will allow. But I haven't been able to pull it out.

Any idea what the pieces of metal on either slide of the key slot are supposed to do? (My guess is that they guide the key into position, and may also be part of the mechanism that keeps you from removing the lock without the key.)

Any idea what I can do to get the key working again? Should I try to drill this loose bit of metal into little pieces, and pull it out? Should I tow the whole thing to a mechanic and get a new lock?

Any advice would be greatly appreciated!

P.S. In case it sparks any ideas, I should say that this problem started immediately after I had repaired the hazard blinker and instrument cluster lights.

I removed the hazard switch, inserted a piece of paper to keep the electromagnet from sticking, and reinstalled it. Then I tested it a couple of times (which involved turning the ignition to "on", testing the blinkers, then repeating).

I also removed the instrument cluster, soldered some wire to the back of the instrument light dimmer switch to bypass it, then reinstalled the instrument cluster. I connected the electrical wires to the instrument cluster and turned the ignition on and off a couple times, to make sure the lights were working. Then I fumbled around for a while to reconnect the speedometer cable, which involved a lot of reaching up and around the ignition assembly, behind the dash. This may have pushed back one of the vacuum cables slightly, but the ignition switch is so firmly mounted that I doubt I could have done anything significant to it during this process.

Once I had finished reinstalling the instrument cluster, I wanted to start the car up to test everything, and that's when I found I couldn't insert the key. The timing is strange, but I think it is purely coincidental. Maybe the switch was ready to fail, and using it 4 or 5 times in a row pushed it over the edge. It's frustrating, because I was looking forward to having working dash lights and reliable blinkers, but now I can't use the car at all!

Thanks for any help you can give!

vstech · #2 02-10-2008, 09:54 PM

do not drill anything.
those bits of metal in your way, are the leaves that make the tumbler work.
my bet is you have a brass key, and it failed... get a new key from the dealer for your car.
does the key work in the doors? all of them. easily? you could try spraying some graphite powder in the lock and see if it eases the insertion.

mfripp · #3 02-10-2008, 11:59 PM

Thanks for the reply. I wish it were as simple as that, but unfortunately it doesn't seem to be. The key works just fine -- it is not bent or worn, and it operates the doors, trunk, etc., same as ever. There are just pieces of metal blocking the key from entering the ignition lock, and it can't get past them to even try to turn the ignition -- it goes in 1/4" and gets stopped.

Any other ideas on this? Maybe one possibility would be to grind a copy of the key down to a thinner profile, so it can get past the metal piece and into the lock, long enough to remove the lock...

turbobenz · #4 02-11-2008, 01:18 AM

The steering wheel lock isnt under and pressure is it? Ive done that before and it took me a while to get the key in

mfripp · #5 02-11-2008, 11:46 AM

Quote:

The steering wheel lock isnt under and pressure is it?

I don't think so. I've tried jiggling it left and right in various ways, as I try to insert the key, but had no luck. I think that would prevent the key from turning the lock, rather than entering it, wouldn't it?

turbobenz · #6 02-11-2008, 11:49 AM

well if you push it into lock position (you know how it clicks) without the power steering running it will be under tension from all the steering linkage and tires. The steering wheel will be forced upon the steering lock and you will not be able to enter the key. But since you were jiggling it, thats not the case. In the case of it being under tension you just have to turn it real hard while inserting the key.

hangit · #7 02-11-2008, 11:54 AM

It sounds like you need to replace the tumbler as soon as you can get the key in. Go to www.dieselgiant.com and follow his ignition lock pictorial. Been there, done that!

John

mfripp · #8 02-11-2008, 12:23 PM

Quote:

It sounds like you need to replace the tumbler as soon as you can get the key in.

Yikes. Yeah, that's what I'm afraid of. Do you know whether it's possible to order a new tumbler that matches the keys I already have? I'm hoping to avoid having to carry around different keys for the door and ignition.

Grdenko · #9 02-11-2008, 01:11 PM

yeah, the tumbler you can order from a dealership with your VIN and it will use the same locks as your doors.

the ignition lock is more sensitive to wear on the key than the door locks so i wouldnt count that out.

my first thought was that the steering wheel lock (if you have one) is keeping you from getting the key in. Sometimes my key gets stuck IN the ignition and i have to pull the wheel one way or the other to get it out, try that out first, dont drill anything!

bgkast · #10 02-11-2008, 03:18 PM

It seems like the leaves are sticky. try using some graphite lock spray, then trying to work the stuck leaf free with a dental pick.

mfripp · #11 02-11-2008, 04:25 PM

Thanks for these suggestions. I'll try a combination of graphite, jiggling the key, and jiggling the steering wheel, and see if that gets me anywhere.

I think the next option after that will be to try to make a thinner, "mini-key", and see if I can get it to go past the blockage and into the actual lock assembly. If I can do that, it may make it a lot easier to get out the tumbler for replacement.

I'll let you know how it goes, probably later this week sometime. Until then, I'll keep checking back for suggestions now and then. If anyone knows where I can find a used tumbler, just to look at how the pieces inside are supposed to line up, that would be helpful too!

hangit · #12 02-11-2008, 04:42 PM

Quote:

Originally Posted by mfripp

If anyone knows where I can find a used tumbler, just to look at how the pieces inside are supposed to line up, that would be helpful too!

The locksmith showed me my bad tumbler. They are thin pieces of metal (leaves) that are spring loaded to match the key cut. Some of your leaves are probably broken. Best to get a new one. Check with your dealer if you want to use the same key, otherwise you can order one from Phil/Roy or any of the parts places.

John

mfripp · #13 02-13-2008, 10:08 PM

Thanks for your advice everyone, you saved me a few hundred bucks and a lot of angst!

I ended up squirting some graphite lubricant into the keyhole, and then jiggling around the key to see if I could get in. Before too long, lo and behold, in it went.

It turns out there are two pieces of metal just inside the key entry (the leaves?). I think are supposed to hold the thick part of the key after it's inserted. They ensure that when you turn the key, most of the force is exerted by the top, thick part of the key, rather than the thin part in and near the tumblers. Got to hand it to those engineers, making sure our keys wouldn't get gradually twisted off over time.

These two pieces are loose, but are usually confined in a certain position. Unfortunately, a little stub of metal broke off the top of the tumbler assembly (and part of one of these little pieces may have broken off too). So then they floated around in there and blocked my key. Once I added the lubricant and jiggled gently for a while, they went back into place, and let me insert the key.

There are pictures of all this below.

For now, I've just removed them and put the lock back together. It works fine, but is much more likely to break off the key now. So I'll order a new cylinder from the dealer soon. But now I know how to replace it.

The next two paragraphs are for anyone who comes along to this thread later.

If you're ever trying to follow the tumbler removal instructions at http://www.dieselgiant.com/repairignitionlock.htm -- I found that the best place to insert the paperclip is just before the key reaches the middle, "on" position. I also found that it was easiest to poke a small paperclip in and out of the notch while searching for the right spot. But the small paperclip didn't seem to go in with enough force to release the outer ring. So then, once I found the spot, I took out the small paperclip, and pushed in a bigger one, until I got the latch to release.

I also found that it took less force than I expected to remove the black outer ring/cover from the lock. With the small paperclip in place, I couldn't get the outer ring to budge, no matter how hard I twisted it with pliers. But then, once I inserted the large paperclip in the right place, and jiggled the ring and paperclip a little, I found that the outer ring could turn easily -- it was only finger tight or less.

bgkast · #14 02-13-2008, 10:42 PM

Glad you got it sorted out, now get that thing replaced!

DeliveryValve · #15 02-14-2008, 04:15 AM

Once you get a new tumbler and a matching original style steel key from the dealer. Get rid of that brass key you have. The brass keys have been know to leave shavings in the tumbler that will cause it to bind. A steel key will not do this.