Ongoing SC no start issue
 

OK guys, I've now discovered my car lacks spark at the plug and at the coil wire. My car originally lost power when trying to drive home on 5 cylinders (big mistake) and the gas in the exhaust cooked my Cat. I figured simple replacement with a bypass pipe and new plugs would fix it. Nope. Where do I go from here, I don't want to continue throwing parts at it without really knowing whats going on...

do a search for green wire (conntects to dizzy).

is the cd/ignition box whining.

When you refer to dizzy, do you mean the distributor? I checked all fuses, and the CD box (~6 inch square metal box on drivers side of engine cptmnt?), it emits a very high pitched tone when ignition key is turned but not all the way to cause the starter to turn. Does that mean the CD is OK? It was rebuilt by the previous owner about 3 years ago

With a Bosch unit at a cost of $900

I did a search for green distributor wire, which took me to the 928 tech forum. Would I have to physically remove the distributor to change out the green wire? Also, it looks like this wire just sort of disappears into the wiring harness of my 911SC. How would I go about connecting the opposite end of this wire, crimp it on? I this wire COULD possibly be the culprit for my no start situation, because my catalytic converter/muffler were both extremely hot when my engine just sort of abruptly shut down. I thought it was my CAT matrix melting/clogging that caused the shutdown, but this no spark issue has me rethinking...

The green wire is actually 2 wires, "a coax". There is one wire inside and a shield wire surrounding it.
It sounds like you have the later continuous wire version that costs a lot to buy...( there is a version made of 2 sections with a replaceable shorter green wire component)
There are different options to repair it if it has failed.
It is held in the distributor with a metal clip.
If you undo the dist and turn it you should be able to get to it.
Test continuity of the wire from the 6 pin connector to the 2 small slots on the plug removed from the distributor.
PM me if it has failed and I can help you fix it.

Thx timmy2, actually I should probably rule out the ignition coil as a potential culprit first, but I'm not sure how to trouble shoot that. I DO own a multimeter. How may I determine the health of my coil?

Measure the resistances of the coil and post your results.
Center to negative terminal,
Center to positive terminal,
Negative to Positive terminal,
Center to case.
Neg to case,
pos to case.

Measured my Bosch coil resistance:
Center to negative 696 ohms
Center to positive 695 ohms
Neg to positive 0.8 ohms
Center to case 696 ohms
Neg to case 0.4 ohms
Pos to case 0.8 ohms

Sounds like it is in spec.

If in spec, what to do next?

I tested this coil with it still in the car, should I remove the coil and do a bench test?

Hopefully the CDI is still good.

Check / replace the green wire.

When I turn the ignition key to on position, but not far enough to turn the starter, I can hear a high pitched tone from CD box, plus I have service records from the previous owner showing that the Bosch CD box was replaced along with the bosch coil about 2 years ago. The green distributor wire appears to be very old (original?)

As posted above, continue to test each component of the ignition and confirm it works as it should.
Green wire as discussed earlier is next in your list of suspects.

If the engine harness is original, the green wire probably is too as the newer models have the single continuous wire without a connector to replace just the "cooked" part of the wire.
Test it and go from there.

How would I go about testing this green wire? Find the 2 ends of this wire and test for resistance with multimeter? Is there some other way to test it?

#1 900.00 for a rebuilt Cdi !!
#2 I had same issues high pitch sound from Cdi it WAS bad
Many on this board repair for about 300.00 or MSD
Just my 2c
Ernie 81sc

In post 6 I told you how to check it. Here's more detail:

You may have to insert a paper clip or similar in each hole of the end that comes out of the distributor as it is very small, just to get a meter probe on it. then unplug your CDI pin connector and 2 of the 6 female connectors correspond with the 2 wires in the green wire coax. Check them for continuity, and check to see they aren't shorted to each other.

If you pull back the rubber boot you will see a white or green wire that is the center wire of the coax, and a black wire that is the shield wire covered in black tubing.

Thanks Dennis for all of your detailed information, I will test this the best I can and get back with a follow up post. Hopefully my headache will help someone with the same problem!

I'm just hoping to resolve your problem for now. :)

green distributor wire
 

I tested the green wire after removing the distributor to check continuity. I used a paper clip in the female terminals from the dist. end of the wire then checked resistance on the 2 terminals of the 6 pin CDI connector. I'm guessing that the the black wire and green wire corresponded to the correct terminal when I got good continuity... 0.4 ohms on 1 part of the coax, 0.8 ohms on the other part.
What now? Check terminal 15/red wire of the 6 pin connector to see that I'm getting power from the battery? Is it my CDI box?

If the CDI is whining you are getting power to it.
Not knowing where you live or the exact year of your car I would guess you should try to swap the CDI box out with a known good one.
Just a thought, is the wire from the coil to the dizzy in good shape and fully pushed in all the way. Sometimes they don't seat all the way. Same with all the ignition wires into the dizzy cap.
What is the resistance across the rotor?
Are there marks on the rotor showing it is making contact.
if the dizzy is still out, what is the resistance of the internal coil of the dizzy? (measure where the green wire goes in, spin to make continuity with the reluctor?)

Are we having fun yet! :)

Thx for response!
I live in central MO, car is 1983 SC
Wire from coil to dizzy is new and worked fine prior to engine shutting down (see beginning of my post)
Resistance across the rotor is 4.90 kiloohms
What is the reluctor?
Is the green wire OK given the resistance values above?
This is an older rotor currently on dizzy, I do have new parts, rotor, cap, plugs, and I was planning on replacing them anyway.

The more I learn, the more fun I have!

LOL, somehow I knew you'd ask! :)
Reluctor looks like someone stuck a spider in your distributor..... (6 legs and all...)
The only place I know of to get one is here:
https://www.gowestyautoparts.com/1978,PORSCHE,911-SC,1262573/Secondary-Ignition/Bosch-Ignition-Reluctor,741-43003-101/
http://forums.pelicanparts.com/uploa...1371016726.jpg

Dennis,
Does it matter if the negative lead is on the male connectors for green wire, or should the neg lead of the multimeter be clamped on one of the "spider legs" while touching the male connector with the positive probe. Sorry to be such a pain about this, but I was getting resis values all over the map, and I think that was only when the neg probe was touching the body of the distributor. Otherwise, I'm getting 0.L on the multimeter. Is that infinite resistance??
Thanks again, you've been extremely helpful with pointing me straight!!

From what you posted it sounds like you have good continuity. An infinite reading would be the same as what the meter says when you hold the probes apart in the air.
Next test would be the cap to coil wire as well as each cap to plug wire.
Plug wires if original should be around 3K or so with the connectors attached. (Check manual for value)
Can you get hold of a known good CDI box to swap out?

Sending you a PM