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300 CE 24V Sportline
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Discussion Starter #1
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
 

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Current, 90 300CE, 92 400E (Sold 95 E320,70 250C, 91 190 2.6, 91 420 SEL, 95 300D, 87 TD)
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Dang! And those are getting rare! I know...300CE 3.0 24v owner! I needed one also.

Got mine from a SUPER COOL BENZWORLD member!
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Are you using a high quality thermal compound and did you remove all old residue prior to installation of each EZL?
 

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300 CE 24V Sportline
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Discussion Starter #4
Are you using a high quality thermal compound and did you remove all old residue prior to installation of each EZL?
Yes to both. I've replaced many of these to test new arrivals and am confident. The weird thing is that these failures started in the last year, after 21 years with no failures. What changed?

Thanks.

R
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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The weird thing is that these failures started in the last year, after 21 years with no failures. What changed?
Something changed in your ignition system setup to cause these repeated failures. My initial guess would be to check and sub in a different but compatible plug set. Ditto on wire set.

Also what about the orange disc and rotor arm driver (i.e. updated metal T style) at the back of the distributor?

Also check the regulator voltage output. IF the regulator goes south, the EZL is usually one of the first victims along with the battery.
 

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W124
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Are you replacing them with new EZLs? (I'm not advocating dropping the cost of a w124 on an ignition module, just asking to get a data point).
 

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Discussion Starter #7
Thanks again.

Yes, my son and I have discussed "what has changed". Answer: new leads (Beru, same as the previous 10 years, new plugs, Bosch non-resistor and new MB cap, rotor and orange disc).

A new regulator was fitted a few weeks ago. Someone at MB Club UK has suggested that there is another regulater, inside the alternator, that could be causing spikes. I didn't know that and shall research.

This morning, we improved earthing between battery negative and chassis. Around 1 ohm now down to almost nothing - 0.02 ohm(?) - maybe not accurate measurment.

More as it happens.

R
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Did you check the new wire boots to make sure they have the proper Ohm rating?
 

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Discussion Starter #9
All new wires, Beru and NGK, seem to have the same 2K ohms suppressor.

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
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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...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.
...
This might explain a lot or everything.
 

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Discussion Starter #11
This might explain a lot or everything.
My thoughts too.

Researching alternatives now.

Any ideas aside from making up from MB parts?

And source for the crimp tool for MB component leads?

R
 

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Discussion Starter #12
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
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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This die looks like a inexpensive compatible clone of the hideously priced Beru tool.


Just out of curiosity, what is the background on your alternator? I'm sort of suspecting it as the bad agent here, based on the fact that you've already gone through your ignition system head to toe.

There should not be any surges, provided your regulator is doing its job . . . . regulating. Do your headlights brighten when coming off idle or seem unusually bright? Those are usually a couple of giveaways.
 

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Discussion Starter #14
No unusual issues with lights and every reason to enjoy a well-sorted car.

This car, aside from its exterior, is as close to brand new performance as I've every known it since 1997 - better by far than when I drove it out of the MB dealer. That is what is so frustrating and the fact that I never know if it's going to start.

R
 

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Discussion Starter #15
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
 

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Beru ht leads fitted last year ,,along with plugs i found them as good or even better than Bosch . To-day we are getting more and more copies of most every part on on our cars .And its hard to tell if they are original makers or not ,other than the quality is poor . .Before i purchased the Beru i went for Bosch ht leads .As soon as i looked at them i could see they were not genuine Bosch . The leads would noy click on to the plug like my old Bosch holders did .And on one lead the spring fell out .These were purchased from a big parts store over in UK . And the company had outlets all over England .
I contacted Bosch and i had to send pictures of the leads to them .Case is on going .
 

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Discussion Starter #18
Thanks plinker17722

Yes to the heatsink compound. I've done this many times so I'm confident there.

The Beru and NGK leads do not "feel" good although the latest Berus did click into place after a bit of a struggle. They feel quite solid this morning.

However, I've asked my UK specialist if he can make up a high quality set (MB original?) and I await his response. I was tempted to clean up and reinstall my old 1991 originals but decided on new.

New MB CPS going in on Friday so I shall risk the drive to the garage. I'll see if he has any means of measuring smooth current supply.

All the best.

RayH
 

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My layman's opinion is to forget the wires as being a problem if the resistance is correct. If you think that spark arcing across a poor connection on the sparkplug would cause the EZL failure, then explain how it works under the load of the rotor creating an arc in the distributor cap 6 times per revolution. Instead of going in deep on the alternator, consider replacing the regulator with a new unit from Bosch.
 

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Have you run a voltage test across your battery at idle with no load and then with all your accessories on? And if so, what were the voltages? Flooby could weigh in, but I'm thinking an overcharging alt could play hell with an EZL.

Kevin
 
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