Ok, so I am very grateful to the fantastic folks here. Tony introduced me to CDI rebuilder/expert Bob Ashlock. I emailed him with my symptom and my diagnostic process. He replied with a very detailed process that validated what I'd learned and took it deeper. My CDI harness pins 7 and 31b read a very low 0.7ohms. Should be 600. I verified the correct terminal positions and multimeter was not set to K - a legit 0.7 ohms. I could not get the green wire connector bracket off with the distributor installed so I carefully cleaned up around the area, turned the crank to align Z1 with the shroud tick and the rotor positioned on the tick on the distributor shell. I marked the position of the distributor on the engine case and also marked the outline of the washer for the hold down/adjustment screw and removed the distributor.

After removing the bracket and pulling off the connector, I measured the resistance on the terminals inside the distributor. There I get 600 ohms. So the diagnosis is "green wire" failure.

timmy2 sent the connector I need today and it gets here Wednesday. I have the replacement Bosch part already. I will clean up the outside of the distributor tomorrow. It turns smoothly and freely and has about 3mm of lateral play. I didn't have a problem setting timing advance so I don't feel the need to disassemble it. Looking inside with a strong light and it looks pretty clean.

Yay! One of the green wires probably measures open. This is a good upgrade. On my green wire, the plug is jammed against the housing strap. 7 degrees BTDC.

When you reinstall the dizzy you will notice that each cog on the wheel is like 25 degrees, so it will be very easy to reinstall it in the same position it was in. You can even play around, to see which gear tooth to use. For mine, unfortunately, the plug is against the strap.

I notice that Early_S_Man routed his green wire/plug around behind (toward back of car) and under one of the distributor cap clamp - see http://forums.pelicanparts.com/porsche-911-technical-forum/300777-78sc-row-something-broke-now-rough-idle-surging-pictures-included-2.html#post2780222

Also Gunther mentions putting tubing over the green wire to protect it but I can't find any other mentions or photos of this.

Ok, the timer jr connector kit from timmy2 arrived. I can determine which terminal of the short new green wire is connected to the white plug a the other end but what I don't know is which is the braid and which is the core? I read timmy2's post here: http://forums.pelicanparts.com/porsche-911-technical-forum/795232-distributor-green-wire-loose-frayed.html#post7895839

but how do I know which is the "green wire"? I haven't cut into my existing wire yet so maybe it will be clear when I do. Are both the outer sheath and the inner sheath green? And if so, is that inner one the one timmy2 is referring to in step 9? I suspect this is the case but want to verify.

Look at the clear connector that goes into the distributor. One will be green. Check continuity to the white plug male and mark the one with a felt pen for location.
The inner green wire of the coax will be the one to connect to it.
Carefully cut the outer green wire sheath making sure not to cut the shield right under it.
The inner “green wire “ will become obvious.
Photo in this post should help. X marks the spot... :)
http://forums.pelicanparts.com/7900442-post26.html

Got it and thanks!

Just to confirm that my inner green wire was exactly as marked in your photo. I don't know if there is variation, I would assume not.

http://forums.pelicanparts.com/uploa...1391910778.jpg

What the heck is going on! I replaced the green wire with the new one and spliced in the connector. (I'll post photos of that later but I used the correct crimping tool and checked continuity as I went, all was well). I reinstalled the distributor and aligned to my marks. That all went well. So I attempted to start er up and nothing, just turns over.

Going back to the engine bay I measure 600Ω on the white connector m(after disconnecting it) on the green pigtail as per spec. However, at terminals 7 and 31b (after reconnecting it) I see "0" on my fluke. However, I see 600Ω on terminals A and 31/1 at the other end of the connector. See the photos below. The first shows the green wire coming into the 6 pin connector to the CDI. The second verifies the orientation with the ridges that align the connector in the CDI - note the position of the beveled corners and compare to photo 3 decal of the pin outs. This car worked perfectly until this issue presented on Sunday and it really seemed like a green wire issue. A and 31/1 run to the coil primary and secondary. Mine *seems* backwards but how could it have worked before and, more importantly, what do I not now!

Green arrow points to green wire at A | 31/1 end of the connector!
http://forums.pelicanparts.com/uploa...1567175345.JPG
Verify connector orientation, red is A | 31/1 and where the green wire and shield are actually connected
http://forums.pelicanparts.com/uploa...1567175345.JPG

http://forums.pelicanparts.com/uploa...1567175345.JPG

Ok, Bentley has an annotated photo on pg 280-9, I'm reversed. The CDI sticker is from the perspective of the male pins on the CDI. So red circle is 7 and 31d. I'll go back and remeasure resistance and verify VAC when cranking. And check for spark.

So I measure 600Ω on 7 and 31d. Cranking I do see about 1.4VAC. Still no start I then pushed the primary lead into the coil to make sure it was properly seated. I did feel it push in about 1cm and "lock". Ah, I thought, I recall that this primary lead connection is a bit tricky.

I attempted to start and it almost kicked in but then died and just turns over.

I went back and reread this thread and my notes. I think I went down a rabbit hole due to measuring across the wrong terminals on the CDI 6-pin connector! Now what I know is:

I do see 600Ω on 7 and 31b as per spec. I also see AC signal on 7 and 31b when cranking - also correct. I do not see spark from the coil primary (testing with a separate spark plug as per Bob's email to me)

This indicates that the CDI has probably failed - which was my first hypothesis when the engine started up nicely, I heard a click and then it died.

So the good news is I have access to a new CDI from a buddy so I'll test that as soon as I can get there to pick it up.

CDI Inventory..........
 

Michael,

In case you need to borrow a CDI, contact me. I got a few of them in my basement.

http://forums.pelicanparts.com/uploa...1567180222.jpg

There is another box of CDI somewhere I am trying to find and have no recollection where I had it stored. Getting old too fast.

Tony

Ok, so I got the replacement CDI installed and she fired right up! At least it was a learning adventure and I installed the green wire with connector - which likely would have failed at some point. And I'll pay much closer attention to terminal locations in the future. Most connectors have pin 1 marked or some other "asymmetric" orientation.

Good to hear you ultimately found the problem.
At least your green wire will be easy to swap out in the future.. ;)
And yes, regarding your earlier question that I didn’t see, every green wire is oriented the same at the white connector.