W210 e320 CDI starting issue

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r11pak

New Member
Joined
Dec 8, 2008
Messages
15
Hi All,

I've got a 2001 e320cdi estate, mileage 217k, had it for 10 years..its nevered missed a beat and it's never broken down on me.

A few weeks ago the car decided it would stop cranking when you turn past the 2nd key position after the glow plug light comes on and goes off.

Thinking back at it now...it wasnt just all of a sudden, it first happen once a few months ago, however at the time, I remember thinking maybe I just didn't turn the key properly, so flicked it back of and on and it fired up.

Then a few weeks ago similar, I had to flick it off and back on.

Until finally nothing.

Having read it might be the starter relay or the entire k40 module playing up (larger black box that the relay plugs into) , I ordered a second hand k40 module with relay from eBay, plugged it in and hoped it would work ... Still no cranking..

Next thinking that maybe it might be a faulty unit I got sent I tried it in another working e320 CDI same year as mine.. my ( old ones plus eBay items) both worked in their car fine. Their relay and module didn't work in mine. So it's not a a relay or module related issue

Then I thought maybe the starter was knackered, so bought a replacement starter... However before fitting it I thought I would double check the starter was at fault ...I manually bridged the starter relay and it cranked straight away... but didn't fire it just cranked...

Using the other working car to compare what was happening I noticed that upon flicking the key into position 3 the purple wire from the k40 module was getting a live feed, however mine wasnt...so next I gave a 12v feed to mine, once the key was is in position 2, ..the car cranked and started straight away... This works say 9 times out of 10... The 10th being it will just keep cranking but not fire.

Having consultanted a Merc specialist they suggested the EIS was probably faulty and sounded as though it wasn't communicating with the ECU, hence there was no live feed to the purple wire, they then asked if the EIS would always accept the key or not, I explained the key was always accepted by the EIS and always turns.
They suggested I send them the key and EIS to have it checked, I did so and upon recieving both they said the internals to the EIS were in need of repair as they were not making proper connections any longer. They had it repaired and even added a new case on the old cracked key fob. They said that they had tested the repaired EIS and now it was all working as it should be.

I got it back... Plugged it all back in and nothing no cranking. So gave the purple wire a live feed whilst the key was in position 2 and instantly the car fired up again. After switching it off I tried again and it fired up with the key . Tried it a few more times and all seemed to be somehow fixed... Drove the car all day switching it on and off .. No issues.. great all fixed I thought ... Tried it the next day (today) no crank.. Had to use the live feed to the purple wire trick again.. went shopping came back to the car.. No crank... Live feed to purple.. Just kept cranking no fire... 6th attempt fired up.. Got home.

Now I'm really not sure as to what it could be, what are my options next swapping out the eis/key/steering luck & the ECU from a scrap car??!

Any comments welcome.
Car has a new battery and no faults codes are being logged when using a Merc diagnostics kit.

Regards


Rupak
 
I take it the steering unlocks OK for you to be able to turn the key? I am trying to rule out the ESL.
 
Hi Bob, thanks for the prompt reply. Yes the steering unlocks fine everytime.
 

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