Yes, always non-resistor. These were NGK.

I replaced the NGKs with genuine MB.

R

Yes, it's basically the same as used for CPUs. In my case it is a tube of RadioSpares heatsink paste.

R

Interesting.

I only know of one thing that will kill these quickly like that. Cranking the engine without spark plug wires or coil wire connected. So I suspect secondary but you tried all that with the exception of the coil. As others have mentioned it may be worth while to replace that. But you really want to avoid doing a shot gun replacement of parts with $500, last I checked if its even still available, part in place. So I would recommend doing the basic checks of resistance on the coil.

If you are assured that the car will run for at least an hour without destroying the ELZ, then bring it somewhere where the system can be checked on a scope. Good luck finding a person who has and can use an automotive scope these days. You may have to purchase a standard scope and buy automotive leads to read the secondary voltage. It might require a learning curve but you can try it out on another car.

__________________
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John Roncallo

this

Yes, always install heatsink paste.

R

Overvoltage can damage electronics. Rig up a high quality voltmeter so you can read it from the driver's seat while driving. Voltage should not exceed 14.5, even momentarily.

Duke

Thanks for that. I've ordered an automotive oscilloscope that might come into play next week.

R

13 July 2020

Hello again All,

Well, I new, secondhand EZL has been installed. I am reluctant to install the "new" 1200 € one from MB until I am certain that the issues are solved. Time will tell.

Since the 3rd EZL failure, the following has been done.

1. New plugs, MB.
2. New leads, Beru.
3. New coil, MB.
4. Complete cleanup of all areas including distributor cap and rotor - only 9 months old.
5. Complete cleanup and reinstall of all earth straps, including the main engine strap underneath.
6. New (Bosch reconditioned) starter motor.
7. New (Bosch reconditioned) alternator.

Of course, I have no idea yet if all this has solved the problem. I shall not have confidence until a year (?) has passed. Even then 100% confidence is unlikely.

Just as before, the car now starts, drives and stops like a new car. Since its overhaul at PCS in 2017 it has never been better. Apart from this costly EZL issue.

Do I notice any differences after this latest set of "improvements"?

Yes, it now starts, even when hot, like a new car. Before, when hot, it would sometimes fire and then not keep running unless I kept the starter motor turning a little longer. That was hardly a problem as it was just a matter of remembering to hold the key in the start position for an extra half second.

However, it now seems to spring immediately into life and settle into an even idle under all circumstances. I shall be doing a more typical run today and shall be able to confirm this with greater confidence.

More as it happens.

And, as always, comments welcomed.

All the best.

RayH

Non-resistor plugs are no longer in production I've heard.

Take a Multi meter and measure the resistance between the top terminal and the center electrode.

If it has ressistance then your best bet is to find new old stock Bosch F8DC plugs on ebay.

My 300SE needed plugs and I found NOS plugs on ebay for cheap.

The plugs I installed are genuine MB, made in France. I think they are Beru.

NGK supplies a suitable non-resistor, I've got the reference somewhere for those interested. Oddly, these EZL failures all happened on the NGK plugs. I can't believe there's a correlation.

And then there's Champion C11YCC,, as stated by MB.

I've used MB, Beru, Bosch F8DC4 and NGK and never noticed any difference.

My last diagnosis will be measurements of the cable between the EZL and the coil. I've already verified this briefly but I'll do it now more aggressively by measuring the resistance whilst moving the cable to see if there's any intermittence.

And so it goes on.

R

R

I'd follow what Christuna has noted.

Our local dealership supplies MB plugs alleged suitable but they are no longer resistor types

Next. Beru Leads a'int what they used to be.

Check the connections at the fuel pump for corrosion. In fact check every electrical connection you can find. Even go to the trouble of changing all your fuses. Any aluminum ones change them out.

Good luck with that car. It's a shame a rare EZL can render it down.

IS THIS A CLUE?

To recap; 3 EZLs blown in the past year despite almost new HT components, including coil.

I had the impression that death was at startup as I was vaguely conscious of a brief "fire" before death. We concluded that, possibly, some electrical surge was blowing these EZLs.

So, the latest measures included checking and cleaning all accessible earth/ground connections. And then a new (rebuilt by Bosch in Spain) starter motor and alternator have been installed.

Of course, I know not if I've solved it until the car does not fail to start for some time; a year, two years?

But, I have noticed one change.

Before, when closing the electric windows (front ones on a coupé - significant current), the revs would drop slightly and then recover.

After our measures and the new starter and alternator, when shutting the windows, absolute stability. No revs drop. Nothing.

I can't get too optimistic yet as the car was always performing like new - better by far than when I took delivery when it was 6 years old with 130k Kms (80k miles) on the clock.

What do we all think about that?

As always, best to all and keep those comments coming in.

RayH

If it were me I'd take one of the old units apart and look for the specific issue that killed it. It's also odd to me it wants non-resistor plugs since those make noise and electronics generally don't like that. Some think one or the other affects the ign due to current draw but that's ignorant. I'd put resistor plugs in but up to you. I'd also be wary of the coil because new does not mean good. I think I'd rather have an old coil that has proven it works than a new one.
If the coil shorts internally it can cause excessive current draw, which may only appear when hot btw. If your transistor(s) in your module have blown I'd just install some external ones.
Back when I was a kid I got tired of points altering my dwell and timing as they burned (and the cost of new points) so I put a pair transistors between the points and coil, problem solved. Transistors make heat so if moved out of the box then your other components will be cooler.
Or just lose the box and put in an aftermarket setup or home made setup. I see your box has a vac line, so if this is how it controls vac advance, and you still want vac adv, then it just got more complicated. Not impossible, just more complicated. I mention these options if that module is expensive and/or hard to find.

25 August 2020

Not exactly an update but a status report.

After 3 EZL burns we've:

> Checked and cleaned all earth connections.
> Installed a new alternator (90 amp).
> Installed a new starter motor.

Has anything changed? No, the car is running like new but it was before the first EZL failures.

To recap, I said that my impression was that the EZL death was on start up. That was just an impression; there is no evidence of this.

EZL death may be happening on shut down. Does this give us any other clue? Not that I can see.

>>> One small difference is that, if the car is idling and one raises the electric windows, the rev counter doesn't move. Before installing the new parts, the revs would drop noticeably and recover.

Any clue here?

To my mind it must just be the grater capacity of the new alternator.

As always, any and all comments welcomed.

Best to all.

RayH

A thought came to me today: Relays can pump a high voltage spike into the cars system when they're turned off. A relay is just a mechanical switch but it uses a coil to create a magnetic field to actuate said switch. When you turn it off it's similar to how the ing coil works; it generates a high voltage spike. Note I said similar, not just like. This is not good for delicate electronics and while I've never had an issue, it can be one. This may explain why your ign box dies on shutdown because you just killed power to some relay(s) that pumped a voltage spike into the system.
So, if you have relays that weren't in there when the car was new, like maybe to control an elec fan or who knows what, it/they may be the cause. It may be that when the ign is on the system as a whole (battery included) can absorb the spike so no harm. If say you hooked said relay to the ignition power circuit so it only works when that's on, now when you turn the key off you just excluded the battery and everything else leaving the ign box alone in a circuit making a voltage spike. A spike looking for a place to go in an isolated system is like a drunk in a bar looking for a fight and everyone clears the room except a 98lb weakling (ign box), which gets punched right in the face. Corny analogy but it was entertaining for me.
Not saying this is it, but certainly a possibility and seems very reasonable to me. So if you have said relays you may want to put diodes across the coil pins of the relays(s). I suggest a Schottky diode because they're faster and will work better than a silicone diode at catching spikes. Just be sure it's rated for a couple hundred volts which I think most are? Then solder it backwards across the coil pins. If soldered fwd you'll just smoke it and/or blow a fuse. The point is the coils voltage spike is reverse polarity so when it fires off the diode is right there acting as a short.
Since we're on the subject, it's possible an oem relay is causing it too. Maybe the spike is getting to the ign when normally it doesn't. I suppose if an ign switch has more than one contact inside it could break the relay circuit a microsecond before the ign? Or maybe whatever oem relay(s) are on a circuit that has a single diode they share but either the diode died or the circuit was moved to that shared by the ign box, or the ign box circuit moved to the relay circuit. Like maybe one or the other circuit stopped working so someone moved it to another spot. Just guessing, but a thought.

Another thought is to simply make or buy a filter for the power to the ign box so it's safe no matter what kind of weird crap is going on elsewhere. Ironically, the filter uses a coil. Basically fight fire with fire. Other weird crap could be something like the coil in the starter is kicking back which would cause it to die the moment you let off the starter which you described. As in maybe the circuit for the starter is connected to the ign, or is somehow bleeding into it. A long shot theory here but if say the spikes only place to go is in the ign switch, which is normally cut off when you release the key. With wear it makes copper and carbon dust, and the key likely has grease for said contacts. Copper and carbon in grease make it conductive enough that a spike just may blaze right through it so the spike that had nowhere to go, now does. Long shot but who knows. So do you try to find whatever gremlin that may be anywhere, or just put a filter on the thing? Or at the very least put a diode on the leads to the ign.

And as mentioned earlier, I'd use external transistors to actuate the ign coil. Option A; have the internal transistor(s) power the external one(s). If you check a now bad ign box and the output transistor(s) are not working the then you could use the pos (or neg) that drives them to instead drive the new external one(s) and save the box. I'd use two transistors because it's easier on the transistor since a coil is a heavy load, at least the coils I've used. Plus if one fails for whatever random reason you're still good to go. I'd assume the factory used two for the same reason?

What you mentioned about the power windows and rpm is a battery thing, so my guess is the new alt is simply charging the batt properly. When the batt is weak it relies more on the alt which is why you see a drop in rpm. If the batt is good it powers the windows with much less voltage drop, it's the voltage drop that triggers the alt to kick in, and how by how much, so the less power the batt had, either old and weak or just low, the more the alt generates and the more it generates the more of a load on the engine.