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'73 450 SLC / '74 450 SL / '01 ML55
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Good to see back on here. Sorry for your newest problem, but this is where I was 7 years ago. My switch gear took a dump while my car was running in my own driveway when I was chasing the same problem as you, mine was in a barn for 8 years. I was unable to find the Pertronix kit on Amazon for you but I did find it on eBay, for only $11 more than I paid back in'13.
You will be happy you did it, even MB got rid of points in'76.
It is "so easy Cave Man's ancestor can do it"
Will find a camera and take photo's for you. Fuel, Air & Spark, then we make it purrrrrr.
 

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1973 450SL
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84 Posts
Discussion Starter #82
Thanks a bunch! I'll order that tonight.
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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10,563 Posts
Will find a camera and take photo's for you. Fuel, Air & Spark, then we make it purrrrrr.
The wiring diagrams from egv107 would be useful too
Better to use those instead of ones Pertronix supplies. I would provide link, but hard to do from phone.
 

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1973 450 SL
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23 Posts
The new version doesn't have the problem of frying if you leave the key on and supposedly has a few other tweaks. I ordered one last weekend from Amazon.

2644224
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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10,563 Posts
The new version doesn't have the problem of frying if you leave the key on and supposedly has a few other tweaks. I ordered one last weekend from Amazon.
Good luck with that. You know that it requires you to change all your ignition wires as well? They have to be resistance wires while our cars have solid copper wires. Not sure how well those wires work with the standard ignition coil/system on our cars. Or if wire sets are available that are made for the engine in proper lengths. They do likely more than double the cost of installing the Pertronix.

I recommend the 1885 because many of us have had long term success with it using the standard copper wires. There is also an LS version (maybe 1887LS?) that may fit better on 74/75 cars.that have different distributor. Never could see why anyone would leave ignition switched on - but if you have to, a simple disconnect solves that.
 

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1973 450 SL
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23 Posts
Good luck with that.
.... well crap! I'm glad I publicly posted my ignorance :D I [wrongly] thought that time must march on and the Pertronix units that I used on VWs for 30+ years surely must have been made better by adding letters and numbers to it by now. But a download of the manual and it states exactly what you said "DO NOT USE WITH SOLID CORE WIRES" (that I also didn't really realize we have).

So a big and humble thank you for setting me straight, I will get it on its way back and find the proper, old-school, proven one :)
 

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'72 450SL, 107.044-12-000422
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282 Posts
Never could see why anyone would leave ignition switched on - but if you have to, a simple disconnect solves that.
Ive heard this before and make sure I don’t leave the ignition on. But I don’t understand how leaving it on would/could cause damage to the pertronix. How would a disconnect be wired in? Might be good insurance in case SWMBO or someone else is driving and doesn’t know not to leave it on.


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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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10,563 Posts
I've heard this before and make sure I don’t leave the ignition on. But I don’t understand how leaving it on would/could cause damage to the pertronix. How would a disconnect be wired in? Might be good insurance in case SWMBO or someone else is driving and doesn’t know not to leave it on.
What you heard is correct. But for our Mercedes, we can't just throw in the Ignitor II. If we do, Pertronix say we need some other type of wires - not our copper cored wires. If we switch to carbon or Mag wires, they will have significantly different resistance to the copper core wires. (for example carbon core wires vary from 3k to 20k ohms per foot! Our wires have almost zero resistance and we have a resistor in one or both ends. (1k or ~6k ohms total)) .How would those wires affect our choice of plugs and coil (we don't even like resistance plugs). And, are wire sets even available with the proper length and end connectors for our cars? I think it opens a whole new can of worms.

We know from experience that the 1885 works with our copper wires, so that is why many of us use it with otherwise original components. This is where I bought my Pertronix parts. Their application chart confirms use of 1885 for 72-73/74 and 1887LS for 74/75. Also says not to use copper wires for Ignitor II . For more on copper wires, read this link to the end! (totally different car and Ignitor though)

As the following quotation says, there is a chance of damaging the Pertronix if two things happen - First you somehow leave the ignition switch fully turned on for an extended period. Second, the Pertronix magnets happen to stop in just the wrong places. There have been discussions on Peachparts about how to overcome this. I didn't find them today. I don't recall any being that good. One was a separate switch (see below). Another was a fuse in the line to the coil (but how would that be sized?) Maybe someone has a better idea? We need power to ignition when ignition switch is on.... except when we don't! Maybe a thermal fuse or something......????? Never been a problem for me and have had the original Ignitor for many years. But no doubt does happen. Leaving ignition on can damage more than a Pertronix, I have read.

Some guys put a hidden cabin switch in-line that is ignition disable for theft reasons, so that can double as ignition disconnect when working on the car w/key must be ON situations...................

Here is an atricle on Pert failure causes pertaining to this situation:

<
** 1. Key is left on without the engine running with a standard Ignitor. If the engine happened to stop in a position analogous to points closed, the Ignitor will continue to try to charge the coil without the coil discharging resulting in excessive heat which can fry the Ignitor. If the engine happened to stop in a position analogous to points open, the Ignitor/coil circuit would be open, no current would flow, and there would be no damage to the electronics. *

2. A low resistance aftermarket coil is used that does not have the resistance required by the Ignitor as stated in the instructions (1.5 ohms for an 8 cyl, 3.0 ohms for 4 and 6 cyl, assuming a 12 V system). The coil resistance is what regulates the current in the Ignitor/coil circuit. Too low a resistance results in too high a current in the circuit that can overheat the electronics. The failure may not happen immediately but the excess heat will shorten the life of the electronics. How long the electronics will last will depend on how much heat is generated. It could be a matter of a couple of hours to a few hundred hours depending on temperature.

3. Polarity reversed when wiring. This will fry the electronics quickly on a standard Ignitor.

NOTE: The automatic shut-off feature in the Ignitor II prevents damage in all three cases above. >>
 

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1973 450SL
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84 Posts
Discussion Starter #89
Update... I've spent numerous hours attempting to diagnose / repair / adjust the D-Jetronic. Lot's of good advice and opinion here, but we're still unable to get it to run properly.

Ordered the Megasquirt FI system, and the Pertronix system. Will install both, and see how that works. Cheaper and easier than chasing obsolete Bosch parts. Not exactly original? Sure. Will it bring it up to more modern spec, and more importantly actually run well? That's the goal...

I would rather drive than tinker.
 
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