THIRD (3rd) 300-24 EZL failure in 1 year

[ray_hennig]

Hello All,

This is a request for any ideas on what might be the cause of the THIRD (yes, 3rd) EZL failure in 12 months.

My son and I will start some electrical diagnosis this morning but I would much appreciate any input from the clever chaps out there.

Relevant information includes:

• Different coil, cap, rotor arm and leads in all cases – first leads old Beru, then new NGK then new Beru. Plugs always non-resistor and correct.
  So I must assume that it is not a fault part downstream of the EZL.
• CPS still measures around 800 ohms as it always has.
  I have maintained the HT system in this car from 1997 to 2019 without incident.
  I know all the basic rules, obviously including thermal paste, clean contacts, etc., etc.
  
• OVP relay different during 2 out of 3 failures.
• Alternator regulator changed after the second failure.
• Before each of these 3 failures, the car was performing like new.
  Perfect starts – as always – I have never suffered from the damp HT problems, even in wettest winter.
• Until July 2019, the HT (and EZL) in this car has been 100% reliable due to fastidious maintenance by me.
• I have had this car for 22 years so I know it pretty well.
  

What do I plan to do now? Basically, diagnostics:

• Read fault codes in search of relevant codes – NONE last time I tested, 2 weeks ago.
• Check continuity of all earth (ground) connections at and near the EZL.
• Check EZL to coil leads.
• Then what???
  THIS IS WHERE I NEED YOUR EXPERT INPUTS PLEASE.

Awaiting any and all suggestions as this is getting TOO EXPENSIVE and I now have only one EZL left!!!

My thanks in advance.

RayH

 

[grober]

As a general comment most mystery problems are down to understandable "assumptions" that connections and components are OK when they are not. You say that you replaced the alternator voltage regulator but the problem may be with alternator leaky rectifier diode/s that break down intermittently injecting an AC component [ when hot for example] My other favorite is a dodgy engine earth strap /connections which are essential for vehicle electrical stability. a couple of guesses??

Starters and Alternators: Common Misdiagnosis | KnowYourParts

Misdiagnosis can lead to unnecessary replacement of a perfectly good starters and alternators, which will cause unwanted comebacks from customers.

www.knowyourparts.com

 

[zipdip]

Well it sounds like a well maintained car and you do know this car having had it for so long,if it was my car I would go with grobers idea about a rectifier pack maybe buy a new one,because with you having lost 3 EZL's and you knowing that car very well.it has to be something frying them ,you have already changed the regulator,so you were thinking along those lines,go one step more with rectifier /diode pack .

 

[optimusprime]

Ray i think you know this,, but all original parts removed , must be replaced with the very same number ,and not just because it looks the same .Now another thing lots of these W124 had problems with the wire insulation cracking up and wires inside shorting in the loom .I would check the loom and cbles for bad wires . Ho and another thing,, as you have replaced the EZL did you replace the heat sink material [white type putty ] on the base before bolting it back on to the car body ?.

 

[ray_hennig]

Just a quickie as we're outside checking earths, cleaning and reinstalling.

Please, where are these rectifier diodes? I thought they were part of the regulator. No?

Wiring on this is pre-bio wiring so reasonably confident. Measuring earths is my current thinking.

Thanks all. More later.

R

 

[grober]

The rectifier diodes are more of an integral part of the alternator construction and their renewal involves a partial alternator rebuild- for that reason its probably easiest to buy a decent reconned alternator that has been bench tested after re-manufacture? replacing a rectifier pack is pretty routine for the vehicle electrician - but they are all different and may have some traps for the unwary/inexperienced. many videos on this on youtube.
Different alternator but principles the same

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[ray_hennig]

This is what we achieved today:

1. We identified that there was resistance of close to 1 ohm between battery negative and chassis - about 5 inches of earth cable. Deep clean, copper grease and now we have about 0.02 ohms. Continuity measurements between battery negative and earth points in the EZL area are now much easier to measure and much lower than previously.

2. We changed the spark plugs for genuine MB part: A0031596803.

3. Refitting the plug suppressors to the plugs was the same pain as I suffered with the NGK leads and the latest Beru leads. The quality of these latest (June 2019 and November 2019) NGK and Beru lead sets is not as good as the 2002 Beru lead set. I feel that the latest parts feel cheaper and they do not snap into place on the plugs so easily and, when installed, seem to pull off very easily.

4. We checked earthing of the coil - now close to 0.02 ohms from battery negative to coil body.

5. Coil primary resistance of new Beru coil measured (if I recall correctly) 0.15 ohms; whatever, it's same exactly as genuine MB item just received from Germany. So new Beru coil measuring exactly the same as unused MB coil. Important to note that this Beru coil was fitted after EZL failure number 2.

For today, that's it. Thinking and waiting for responses before next steps.

Thanks again and best to all.

RayH

 

[ray_hennig]

Some kind person asked when these EZLs are failing. The car never dies on the road. It never stops. It just doesn't start again.

Each time, as I turned the key to start, I had the feeling that it fired and then died. And that's it; nothing, dead EZL.

Is this a clue?

Is there some surge at start up that's killing these things?

I recently - after failure 2 - replaced the ignition lock/switch with a brand new MB original. I did this because some internet person suggested that a faulty ignition switch could leave 12v on the EZL when the car was off - doubtful, I thought but I had thenew switch and it's now in there.

Still thinking.

Thanks again to all.

R

 

[grober]

Later versions of the EZL units had a limited ability to store fault codes. After 8 ignition switch-ons with faults present the EZL prevented engine start till the faults were cleared. Have you tried reading/cancelling any ignition fault [ blink] codes?

http://www.diakom.ru/CARS2/pribor/cs1000/manual/cs1000_mb.pdf

ps PLEASE ignore if this doesn't apply to your car
pps you haven't got an aftermarket [ ignition isolating] alarm system fitted have you?

 

[ray_hennig]

ps PLEASE ignore if this doesn't apply to your car
pps you haven't got an aftermarket [ ignition isolating] alarm system fitted have you?

The alarm system was fitted by MB in 1997 as the original appeared not to work. I have deactivated it and still no start.

Over many years I have had a 17 blink code - crank position sensor. It's never caused any issues and we saw that I had noted this error back in 2013, 6 years before the first failure.

Coincidentally, I have booked the car to have my brand new MB crank position sensor fitted next Friday - if I dare install my last EZL for the 4 km journey to the garage.

And thanks, yes, that PDF I already have, plus others, that describe to codes.

R

 

[ray_hennig]

Sunday 14th June update:

Checked all around diagnostic socket wiring, measured relevant earths etc. All appears good.

My only worry is the cheap-feeling brand new Beru plug wires. Similar to those that were installed (brand new NGKs) during EZL failures 2 and 3. Again, I had no trouble with older Beru wires installed 10+ years ago - WHY DID I CHANGE THEM AND BRING ON THIS MISERY???

So, the only thing I can do is get hold of a genuine MB set of wires and hope for the best.

And possibly get a new alternator to assure the smoothest current delivery.

Yes, I could find a true expert who could run diagnostics - oscilloscope etc - on the system to look for any voltage spikes that may be the cause of these repeated failures.

New 1200€ EZL now installed and car started from cold with its usual perfection. It's like new!!!

I'm not going to use the car for a while as I reflect and plan.

Huh.

R

 

[ray_hennig]

This is my reply to a US forum ...

I'm thinking on the lines of voltage spikes, regulator etc. New regulator installed after 2nd failure. 3rd EZL dead.

Voltage readings have already been verified as OK but I'm unable - no 'scope - to read transients. Shall talk to a local garage chap on Friday.

To recap, these 3 EZL failures occurred after I'd decided that new plugs and leads were a good idea. Why did I do this?

I did it because we all agree that 1st class ignition components are vital with these cars.

My recurrent thought ...

Each failure is on start up. NEVER when driving. It never stops. It just doesn't start. I never know now, for example, after 2000 kms of perfect performance, whether or not it's going to start. After spending a fortune getting this car just right, this is grim!

More than that, I have the impression that, each time, it fires on start up and then stalls. Then nothing. Dead EZL. New one installed this morning, perfect start. BUT FOR HOW LONG???

I'm tempted to change the alternator.

I'll put in a new OVP for peace of mind.

Once done, only time will tell.

What I want is a 'scope display of transients that could be killing these EZLs. Only when these are eliminated will confidence be restored.

Is this making sense?

R

 

[grober]

https://m.littelfuse.com/~/media/electronics_technical/application_notes/varistors/littelfuse_suppression_of_transients_in_an_automotive_environment_application_note.pdf

some background

 

[Deadly Dave]

If you think it may be voltage spikes then to test this theory how about fitting one of the anti zap protectors. They are used when welding a car to save having to disconnect the battery.

 

[ray_hennig]

If you think it may be voltage spikes then to test this theory how about fitting one of the anti zap protectors. They are used when welding a car to save having to disconnect the battery.

Voltage spikes is my last remaining and most logical conclusion. A new alternator beckons.

R

 

[ivan1983]

Probably one of the first things you did but is there adequate thermal paste on the EZL to ensure the heat is conducted away?

 

[ray_hennig]

Probably one of the first things you did but is there adequate thermal paste on the EZL to ensure the heat is conducted away?

Thanks for your interest.

Yes, the heatsink compound should not be a problem.

I've largely discounted heat issues as I've install these things a few times, always obeying the rules. Also, these cars were exported to Saudi and I'm not convinced that Dordogne temperatures will be an issue. Yes, the engine compartment can get pretty hot but air flow on the move should help dissipate that. When switched off, the temperature around the EZL will rise due to engine temperature but will start to fall as current is no longer flowing.

And I feel that mine are failing on startup, certainly not when running. The car fails to start but performs like new when running.

A new alternator is on the way.

All suggestions welcomed.

RayH

 

[grober]

Only other place I can think of where harmfull ARC RF might be generated on startup would be the the main pre-engaged starter solenoid contacts if they were badly worn/burnt. THIS would mean removing the SM and part stripping it to examine/clean said contacts. Unfortunately IIRC starter motor removal in the M104 NEEDS A SPECIAL LONG SOCKET.
Pre-engaged Starter Motor (Automobile)

 

[neilrr]

What is the part number of the EZL that keeps breaking?

 

[ray_hennig]

What is the part number of the EZL that keeps breaking?

First one to go: A0125452132
Second and third: A0105459532

Now installed: A0125452032

R