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1986 560 SL
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Discussion Starter #1
A couple months ago I started a thread bemoaning various bits of dumb engineering on the 107. A few members agreed with me but the general response was kinda love-it-or-leave-it.

In a more recent thread I revealed how I cranked my engine with the high tension lead detached, thereby damaging the EZL ignition control unit. A new EZL goes for $2000+ from discount sources. Luckily, I found an outfit in Florida (Mercedes Benz Accessories) that I hope will be able to rebuild my EZL for $500.

Now, I ask you, who would design a system that has a catastrophic failure mode like this? Sure, I was foolish to detach the lead but an accidentally detached or broken lead would have the same effect. Ditto a missing rotor or distributor cap. Or even improperly seated plug wires. Anything that interrupts the high tension discharge.....

By way of consolation, the guy at the Florida repair shop told me I was lucky my SL is old. He says jump starting a new one results in $3000 damage.

Seems undeniably dumb to me.

I'll hunker down for the counter-barrage.
 

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2017 Police Interceptor Utility, 2017 Police Interceptor Sedan
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Well, you bring up a good point. How much protection against improper operation should there be? I suppose Mercedes didn't consider someone might try to crank the car with a removed coil wire. Nor did they think someone would misseat ALL 8 wires.
 

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2001 SLK320, 2001 C320
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However...it's considered SOP (standard operating procedure) to ground out the coil wire any time an engine is cranked with the coil wire disconnected. This applies to ANY car...not just Mercedes.

(However, you're listening to a guy who burned up a Mustang wiring harness while trying to replace a ignition key cylinder with the battery connected. *cough* *cough*
 

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1973 450SL
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651 Posts
I think you're right, Dugald, the ignition system should be bullet proof but it isn't. The vacuum system shouldn't be run thru nylon lines, but it is. I'll not get into whether the entire car should be run off vacuum motors. Oh, I guess I just did.
I love the look of these 107s but if you pull back my sheetmetal and upholstery, you're not going to find Mercedes under it any longer. Can't wait for the rear diff to give out. A nice corvette independent would be a lot of work and expense, but it would have inboard brakes and be serviceable..........
There's lots more...
 

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1986 560 SL
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Discussion Starter #6
flyboyike said:
Well, you bring up a good point. How much protection against improper operation should there be? I suppose Mercedes didn't consider someone might try to crank the car with a removed coil wire. Nor did they think someone would misseat ALL 8 wires.
It all depends on your design philosophy, Ike. I once worked on automated public transit systems where the aim is to design everything either fail-safe or fail-soft. That's how things are done in mission-critical systems, aircraft included. As for Mercedes, I believe an incomplete high tension circuit - however caused - is a foreseeable and plausible fault that they should guard against.

That's this fool's view anyway.
 

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'80 450SLC Afro RHD Ikonengold
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A fault in the cable AND say a gap of a 10-12mm (1/2") would cause spark and offload of magnetic energy.

Problem in your case is unsolvable/unprotectable, at least not in the penultimate decade of last decadent millenium.
When EMF is created in the coil, secundary windings induce HV that creates spark. By discharging induced current trough spark, energy pushed into coil is taken out trough a "massive drain".
When primary coil pushes EMF energy into the coil, it may induce some voltage too but since it is drained elsewhere, virtualy no feedback is created.
Now, without ANY drain, all the energy goes back. But it's not that simple. Coil is somewhat like a pendulum and have some kind of inertia (to simplify) and pushing in 12V creates more than 12V back in a spike (like 3-10 times more) AND of a reverse polarity.
Since there was no switchable component (electronic breaker) in '80 that could sustain that, warning was issued.

I do not want to say it is your fault so WTF. It cannot be your fault as everyone would probably make same mistake, including me! IMHO, I tought that bridging the cable was purely to control runaway spark and avoid fire. But it cannot be Merc fault either, not at least to the extent you feel.

___________________________________________

RE: R129 that is fried if flylead jumstarted... most of the new cars are like that (except that Merc leads the way so obviously in the era of "fail-proof carburator common engines" merc had electronics that can be fried). All it takes is that power donor car has lights on (so to make sure alternator is on hence provides smooth power loss compensation = no surge).
 

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1986 560 SL
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Discussion Starter #8
Well, if I knew then what I know now. I thought removing the lead altogether would preclude spark hazard. Didn't consider feedback....
Meanwhile, a fuse or diode could could block overvoltage feedback, no?
 

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1986 560 SL
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Discussion Starter #9
mbslns said:
I think you're right, Dugald, the ignition system should be bullet proof but it isn't. The vacuum system shouldn't be run thru nylon lines, but it is. I'll not get into whether the entire car should be run off vacuum motors. Oh, I guess I just did.
I love the look of these 107s but if you pull back my sheetmetal and upholstery, you're not going to find Mercedes under it any longer. Can't wait for the rear diff to give out. A nice corvette independent would be a lot of work and expense, but it would have inboard brakes and be serviceable..........
There's lots more...
Craig, I get frustrated by Mercedes' pretentious and often feeble engineering (Take that you apologists!!), but don't get me started on GM's sorry efforts. Disasters like my POS Yukon are why Toyota has eclipsed GM.
 

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'80 450SLC Afro RHD Ikonengold
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dugald said:
Well, if I knew then what I know now. I thought removing the lead altogether would preclude spark hazard. Didn't consider feedback....
Same idea I had ever before




dugald said:
Meanwhile, a fuse or diode could could block overvoltage feedback, no?
Yes, and there is protection of that kind.
No, the nature of feedback (simplified) is that feedback is too long for those components to recoverably sustain it. In normal operation thier 'work' is part of the heat created by the unit.

In your case, very likely those protective components are short. If not switching transistor is dead short. I doubt rest of electronics are faulty.
If your EZL is 'openable' and you can access/replace components inside, a good electronics guy could repair it (like tv repair guys).
I repaired successfuly one very old electronic ignition for K-Jetronik (450) as components were on a plain PCB (and switching transistor I used was BU326) and I keep it as spare.
 

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1986 560 SL
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Discussion Starter #11
Djenka, I haven't removed EZL yet but it must be openable since the shop in Florida makes a business of repairing them. The trick is figuring out what's wrong absent a circuit diagram or schematic of the box's internals. Our Florida friends want 1 1/2 hours labor to diagnose the fault.
When I remove it I'll see I can get in it without a can opener. I'll look for obvious shorts, etc.
Thanks for your informed interest.
 

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1973 450SL
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flyboyike said:
When you find one that is, let me know.
GM style HEI is one. Every manufacturer has it's successes and failures. HEI isn't 100% but it's the most reliable out there in my experience.
It's just that Mercedes compounds their failures by making repairs very very expensive, even if we're just talking parts.
 

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1973 450SL
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dugald said:
Craig, I get frustrated by Mercedes' pretentious and often feeble engineering (Take that you apologists!!), but don't get me started on GM's sorry efforts. Disasters like my POS Yukon are why Toyota has eclipsed GM.

See, it's all personal experience. I have a 2K Yukon Denali that has never left me beside the road when the ignition system crapped out (Mercedes.....).....
 

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81 380 SL. 98 lexus GS 300 2000 Toy tundra
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A couple months ago I started a thread bemoaning various bits of dumb engineering on the 107. A few members agreed with me but the general response was kinda love-it-or-leave-it.

In a more recent thread I revealed how I cranked my engine with the high tension lead detached, thereby damaging the EZL ignition control unit. A new EZL goes for $2000+ from discount sources. Luckily, I found an outfit in Florida (Mercedes Benz Accessories) that I hope will be able to rebuild my EZL for $500.

Now, I ask you, who would design a system that has a catastrophic failure mode like this? Sure, I was foolish to detach the lead but an accidentally detached or broken lead would have the same effect. Ditto a missing rotor or distributor cap. Or even improperly seated plug wires. Anything that interrupts the high tension discharge.....

By way of consolation, the guy at the Florida repair shop told me I was lucky my SL is old. He says jump starting a new one results in $3000 damage.

Seems undeniably dumb to me.

I'll hunker down for the counter-barrage.
I was searching forums and came across yours. I purchased my 380sl from a friend of mine.He had the car in storage for about a year. He had mentioned that the last time he worked on the car he said that he wanted to prime the TC tensioner with oil so he removed the coil lead and turned it over..... Fast forward to today I now have the car and am having a hell of a time diagnosing issues with timing. My mech says that I need a new dist(800.00) from Benz or 500.00 aftermarket.My question to you is what symptom was your car showing to believe it was the EZL unit???
thank you in advance
Scott
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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9,867 Posts
A couple months ago I started a thread bemoaning various bits of dumb engineering on the 107. A few members agreed with me but the general response was kinda love-it-or-leave-it.

In a more recent thread I revealed how I cranked my engine with the high tension lead detached, thereby damaging the EZL ignition control unit. A new EZL goes for $2000+ from discount sources. Luckily, I found an outfit in Florida (Mercedes Benz Accessories) that I hope will be able to rebuild my EZL for $500.

Now, I ask you, who would design a system that has a catastrophic failure mode like this? Sure, I was foolish to detach the lead but an accidentally detached or broken lead would have the same effect. Ditto a missing rotor or distributor cap. Or even improperly seated plug wires. Anything that interrupts the high tension discharge.....

By way of consolation, the guy at the Florida repair shop told me I was lucky my SL is old. He says jump starting a new one results in $3000 damage.

Seems undeniably dumb to me.

I'll hunker down for the counter-barrage.
This is actually a problem with alot of cars. I dident think MB had this problem but it is common especially years ago. The real problem is that for an MB its $2000.00. For a Ford its $49.95.
 
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