Intermittent issue starting - PeachParts Mercedes-Benz Forum

MitchTX · #1 07-10-2014, 10:28 AM

My '98 E300TD is giving me trouble with starting, related to the key and/or ignition. When it gives me trouble, I'll insert the key and turn normally but the glow plug light (and probably others, but that is the light I look for) does not illuminate, so no start. If I turn the key to start, nothing happens. When this first started I'd turn the key all the way off and try again, eventually it would work.

Recently I started just wiggling the key and have found that will usually work as well. The glow plug light comes on, then goes off after a bit, and then I can turn the key the rest of the way and start the car.

This problem comes and goes. Last week I thought a few times I was going to have to towed, but then finally things worked and it started. This week most of the time I'm not having the issue at all.

I'm open to any and all suggestions on how to find and fix this issue.

TMAllison · #2 07-11-2014, 09:56 PM

Is the chrome beauty ring around the ignition loose? It can be tightened with two fingers. Happened to me once and had similar problems until it was snugged up. Receiver and transducer not aligned close enough to conduct their security handshakes so no joy when the key was turned.

Could also be a fuse on the top of the K40 relay making intermittent contact or the K40 itself.

The ignition system has ~200k rolling security codes in its memory. Eventually as these cars age they will need replacement ignitions, new keys, and some star diagnostics work to marry the replacements.

MitchTX · #3 07-16-2014, 08:55 PM

The beauty ring does not appear to be loose. I tried to wiggle and turn it, but it didn't want to move. My car has ~ 165K miles on it. I recall watching a video on cleaning the K40, I'll look into that again. Of course it has not acted up since I posted this question.

jay_bob · #4 07-16-2014, 09:47 PM

Quote:

Originally Posted by TMAllison

The ignition system has ~200k rolling security codes in its memory. Eventually as these cars age they will need replacement ignitions, new keys, and some star diagnostics work to marry the replacements.

I had no idea that it would eventually run out of codes. I thought the key had 3 parts. Here is how I understand it works, if I am wrong please let me know.

DAS chip - which I thought was a basic RFID rice grain chip. These are (in many cars - Hondas I know for sure use this) the same exact chip they inject under the skin of your dog or cat. This is what the coil in the lock assembly is for, it sends energy to wake up the chip, and then reads back the code. It does not rely on the batteries in the key, the batteries are for the RF and IR systems. It is, afaik, the same code read back every time. If the code matches what is stored in the computer, you get the "zzzzt" sound and the key and steering wheel are free to rotate. It also passes the permission to the engine management system to deliver fuel, shift the transmission, etc.

The (at least 98+) key switch module is the gateway between the power train CAN bus and the body CAN bus since it speaks to both systems.

My wife's W164 and my W210 use the same key system. In fact the keys look identical as I have a replacement key for my W210. If I try to put the W210 key in the W164 it pops up a message on the console that says 'This key does not match this vehicle' or something like that. The W210 just sits there and does not give the "zzzt" sound or unlock the wheel if I put in the W164 key.

RF unlocking system - upgraded in the 98-99s, the 96-97 210s used an entirely IR based unlocking system. This I have to believe uses a rolling code but normally systems like this have a table of 256 or 512 codes that repeat over and over.

IR system - holdover from the 96-97s, it will unlock the car and open the trunk. Only IR can do the auto open/close of all windows and sunroof.

There appears to be an IR receiver in the keyhole, but I am not sure what its purpose is.

In 98 they deleted the big IR receiver in the rear view mirror with the huge red/green LEDs since now you do not have to aim the keys at the car to unlock. There are small IR receivers embedded in the door handles on each side since all they do is handle the convenience functions.

The only thing I have heard about limits with this system is something about a maximum of 8 keys being registered to the system over the lifetime of the car.