EIS problem? W202 ignition live/ dash lights intermittently dying causing non start and/ or stalling.

[charlysays]

Hi all,
So my fathers 1997 facelift C250 TD is playing up. Its got steadily worse over a year or so.
The symptoms are:

Key inserts into EIS no problem and always unlocks the steering lock.
Everything works fine in position 1 (accessory).
In Position 2 (ignition) is where the problems start.
It began with occasionally no ignition lights and no crank. Literally like ignition live has been disconnected so no dash lights in position 2 and then no crank as a consequence.
Now it's so bad the car is disabled.
After many attempts the dash lights will sometimes stay on allowing you to progress to starter and start it but it then often stalls (dash lights going out) when putting it into drive or even pressing the brake.
Often the dash lights will go dead when you go from position 2 to starter.
Other times it just stalls without touching anything.
Other times you can drive it miles.

I have noticed that if you apply a slight pressure to the key as you turn it, in towards the steering wheel or left side of the car, that it will more reliably start. This is the only nuance to the problem which I've noticed. Other than that there's not much rhyme or reason as to how exactly it will fail to start/ keep ignition live going. It does appear to become more reliable the more times you try it which makes me wonder about a bad relay or other contact.

The key has been replaced and was not the problem.
I've taken the case off the EIS and cleaned the PCBs and what looks like a mechanical contact which interacts with the turning barrel of the EIS (not sure exactly what this does- does it work like an old style ignition barrel in this respect?)

I've watched this video on cloning the EIS but I wonder if a bad relay could cause this before I get to swapping the EIS chips (I'm quite used to de-soldering and re-soldering EEproms like these when chipping ECUs).
K40 relay? Any other relays I should check?
What could cause the dash/ ignition/ engine to go dead intermittently like this?
It's not an Immo problem, I'm familiar with those having chipped and immo off loads of these ECUs- the dash lights stay on with immo issues, just no crank and no start.
Many thanks

 

[charlysays]

So I found this... all my research is still pointing to the EIS but specifically the mechanical contacts in the tumbler.
This thread details how to clean them. Should do the trick hopefully and a lot easier than cloning it by de-soldering the two chips which look to have about 60 legs lol.

https://www.slkworld.com/threads/eis-internal-switch-cleaning-quick-version-fixes-morning-no-crank-problems.592049/

 

[charlysays]

OK so I tried cleaning the EIS... couldn't get it apart. Suspect lots of the ribbon cables plus through hole solder joints will need de-soldering to get this early EIS apart. The How To in the forum link I posted above is a newer EIS in which the barrel and tumbler aren't completely encased by PCBs. I will continue to work on this once the car is running again though as it will probably become a significant problem as the car ages- I need to be able to replace those microswitches in the barrel- any used EIS I fit, the microswitches probably won't be in the best shape either so it's just buying time rather than a permanent fix.

I then tried transplanting both MCUs from the faulty EIS into a good used EIS but that didn't work either (and was a load of fiddly soldering with associated heat stress on the PCBs and components). I then noticed that one of the MCUs on the replacement EIS had a different number to the one I soldered in, which will explain why it wouldn't work. A different MCU I.D most likely means the legs do different things- no play.
Before I started this job I made the mistake of not unplugging the ESL in the disengaged position... So I reunited the cars original EIS with its MCUs (brains basically) and remade the joints I'd de-soldered to get it apart. It worked, recognised the key and unlocked the ESL which I promptly disconnected (horn went off at this point lol- some kind of security feature to say don't mess with my ESL?).
Even though it was ultimately a needless exercise I'm quite chuffed that I managed to partially disassemble the EIS, de-solder it's MCUs twice and solder them back in twice and get it working as well as it did before. I really expected to have killed the MCUs in particular with two doses of 350 celcius heat gun to de-solder them although I did use kapton tape and foil tape to protect the PCBs and the second time I de-soldered the MCUs I put both kapton and foil tape on the ceramic chip body itself in the hopes that it wouldn't get too hot.

So my plan now is to fit one of my Immo off ECUs (plug and play between all C250 TDs), fit an ESL Emulator (£25 quid off ebay and they seem to work) and fit a replacement used EIS (I have two to choose from one with two keys which is fairly low mileage the other has 3 keys but had 250k miles on it).
This should get the car working normally again (and with spare keys) minus its steering lock.

I will need to have a chat with my MOT tester but I don't think it will fail according to the rules.
MOT website says that it's acceptable for the steering lock not to work providing there is another form of immobilisation.
There is another means of immobilisation- if the EIS doesn't recognise the key, it will not allow the tumbler to be turned. If the tumbler can't be turned, the transmission can't be taken out of park. So the steering lock can be safely bypassed without any MOT issues etc.
Will update later in the week once I've hopefully got this all working, then it's "reverse engineer" the faulty EIS to work out how to get it apart to the point I can replace the microswitches which the tumbler acts on.

 

[charlysays]

Problem fixed. Esl emulator worked a treat, immo off ECU worked a treat (done about 10 now and they've all been spot on), used eis with two keys starts unlocks the car etc, working perfectly. Immobiliser is still intact- unless the key is recognised you can't get it out of park .
Wish I hadn't messed around trying to transplant stuff via soldering but in my defense I didn't know about the esl emulators.
All's well that ends well. Best keep an eye out for a couple of good used 2105450008 eis with two keys to keep for a rainy day .