Coil wire

[MarkCan]

71 280 motor fitted with the 0 231 116 066 Bosch distributor.
I was able to partially recondition the distributor. New points, cap, finger and the plug wires. I’m little unsure when it comes to the supply - cable going from the coil the the distributor. Original is beyond help so I cannot measure anything of it. I have a used one in well used condition from the 230 and it is just over 9.4 kohm. New one from the aftermarket set is 6.1 kohm. Plug cables are 4.8 kohm. Blue Bosch ignition coil (well used).
Now, we are talking just around 11 kohm resistance for the current setup. That is well within the Mercedes suggested 13 kohm max.
From what I was able to test yesterday electrical performance is very poor. (Engine is easy to start, runs on the rich side though). Spark is on the weaker side. Coil saturation is very inconsistent and that is definitely effecting the burn time, (which I was able to confirm with the scope).
At this point I would like to finish what I started. I may still get the A123 complete distributor but for now the challenge stands. This system needs get 100% on the test before I move on. I think, I’m close but I would like to ask your opinion on the remaining pieces of the puzzle. Will lowering the combined cable resistance down to 6 kohm make that much difference? One thing for sure, I’ll still put a new coil and run the new ground for it. Should I go for more powerful unit?

[Pawel66]

Mark, there are plenty of posts on this on the forum. In summary: no resistance anywhere except spark plug connector. Copper core leads. I am attaching a chart on other topic, but it gives the type of spark plug connector. Stay away from Beru plug connectors, get Bosch, just my opinion.

[wwheeler]

The replacement rotors have a 5K resistor built in. Not sure about the originals. The resistor is located where the reddish epoxy is between the center and the rotor tip. Measure the resistance on a rotor and you will find 5K.

[Benz280]

 Ignition Coil. For what's its worth.
Although my existing original coil was working just fine ( I thought ), looked a bit old and tired . I replaced and feel a difference at higher RPM. Engine seems to respond better, a bit more torquey .
So I guess the message is, if your coil looks old and tired, for a small price you might see a performance increase. 
   

[mdsalemi]

Ignition Coil. For what's its worth... if your coil looks old and tired, for a small price you might see a performance increase. 

When I installed the Pertronix system I also installed their Flamethrower II coil, which has considerably higher output voltage than any of the stock Bosch coils. It seemed to be the right thing to do.

[MarkCan]

Will lowering the combined cable resistance down to 6 kohm make that much difference? One thing for sure, I’ll still put a new coil and run the new ground for it.

I guess we are about to find out.
Parts are on order and should be here Friday.

[mnahon]

I measured the resistance of a new Bosch replacement rotor, and it is, indeed, 5K ohms.

[wwheeler]

Yeah, that was a weird finding for me. I wondered why they had the epoxy on the rotor and never occurred that a resistor would be hiding underneath.

[MarkCan]

DHL just up the bar, they delivered the goods in lightning speed
Now I have no choice, new coil is here. New cables will be here Monday. I guess I’ll go and rob my W126 out of that coil cable. I hope Cliff doesn’t mind 🤫.

[MarkCan]

Yes, it does makes a significant difference.
Take a look how well the coil V cleaned up.
First event corresponds to cylinder 5 and than the rest follows the combustion sequence. (5,3,6,2,4,1)

More to follow,

[Benz Dr.]

Your coil wire could be a carbon core. Get rid of that and get a wire core with no resistors. Then you will achieve the optimal 6K ohms total system resistance.

[MarkCan]

Your coil wire could be a carbon core. Get rid of that and get a wire core with no resistors. Then you will achieve the optimal 6K ohms total system resistance.

You are absolutely correct. That’s what they are. New set is not here yet.
I put new coil in. What a difference,wow. I also made a temporary low resistance wire for the king lead. Current rotor looks new but it’s got 3.4 kohm resistance. Than the spark plug wires on top of it.
I’ll put a set of used but good NGK BP6ES when the wires arrive. New on order as well.
With all the maintenance and improvements so far my rpm climbed to 1200 when the engine is up to operating temperature. I have not touched any adjustments on the IP. From what I see someone try to compensate for poor running fuel supply with volume.
Now with the engine running healthy is time for me to go back a step and go over the linkages more carefully. The linkage tour is where I’m going next.

[MarkCan]

Since this is becoming more of the general engine setup saga I’ll start a new thread for it.
https://www.sl113.org/forums/index.php?topic=33481.0