No spark.... wierd problem.

[Tspringer]

My demon possessed '69 911S hotrod is still not running. No spark.

So, using the wiring diagram in my trusty haynes manual, I started to track down this seemingly simple problem. I thought I had it licked quick.... I found that it was not hot at the coil. On the positive coil terminal with the key on, there is no power.

So I started tracking that. Except I cannot. What the heck is an "Oscillating SCR" anyhow and where on earth is it located? I think I have many more wires than I am supposed to have in this car.

According to the diagram I have, there is supposed to be a blue/yellow wire and a black wire going to the hot post on the coil and then a ground wire to the other post. Mine seems to wired properly...... but no power at the coil and no spark.

I dont really trust the diagram in the Haynes manual. IT shows more wires exiting from a number of the other gizmos in teh car than exist on the actual car.... and in some instances not enough. There are clearly differences. The wiring diagram on the Pelican site labelled 911S '65 - is also clearly wrong, it has no CD box.

So.... anyone have any idea how the ignition circuit on this freaking thing is actually supposed to work?

I was going to post some pics, but when I went to shoot them the digital camera broke. First problem with it in 3 years. I told you this car is possessed!


Terry

[B D]

Take a deep breath, I feel your pain I just cleaned up the birds nest of wires the PO left me with, I also upgraded to an MSD box and Crane electronic ignition. The 65 diagram is correct there was no CD box I believe until 69. Just take your time and sort things out piece by piece, leave it for an hour and come back if you get frustrated or lost. Also mark every wire with some tape and a description of what it is and what it was connected to on both sides of the wire.

[Early_S_Man]

Terry,

Your car has a CDI, right???

It ISN'T SUPPOSED to have 'battery' on the 'hot' side of the coil with only the ignition switch on ... since the CDI ubit supplies millisecond-duration 460 Volt pulses to the coil every time the points open!

I strongly suggest that you look at, print, and carefully read the Bosch CDI documents I posted in the following thread:

Perma-tune CD or Bosch CD?

You probably also have a ballast unit between coil and tachometer ... one of those 'extra' wires.

Here is a simplified diagram that may help ... '69 vintage with MFI and CDI, ballast-equipped, only!

[ruf-porsche]

Check the point in the dizzy to see if you still have a gap.

[Tspringer]

Warren,

Thanks for the diagrams and links. Great info there!

My car appears to be wired correctly according to the diagram, with one question or exception.

The red/white wire shown as running from the coil to the ballast unit I am not sure of. On my car this has been replaced apparently. I have a seperate solid red wire attached to the coil that runs back to one of the 4 pin connectors at the rear of the engine bay on a '69 model.

When I got the car, this red wire was the only wire connected to the left most pin connector and it was simply pushed into one of the holes and held in place with a glob of tar like insulation stuck to it. Crud, but it did work and the car ran great.

So, I am not sure which hole this wire is supposed to connect too in this old pin connector and Im not sure how to test for the correct wire because I dont know where on the car this ballast unit is located.

Also.... it would seem that even if the red/white coil to ballast connector wire was not attached the car would still have spark but the tach would not work. I have no spark.

Everything else appears to be wired as per the diagram above.

Any ideas? Im thinking hard on just converting to an MSD unit and being done with it.


Terry

[Early_S_Man]

Terry,

I always suggest removing the CDI unit from the electrical panel and clean the ground lugs and terminals ... likewise for the Faston connectors A ... D, and the coil and connectors. Do a search on "CDI bench test" to read some more details on my suggested troubleshooting methods.

The exact factory color schematic you need is available at Sherwood Lee's page ... you need SL33Left and Right:

http://members.rennlist.org/911pcars/WiringDiag.htm

The ballast unit should be mounted on the electrical panel ... trace the wires from the positive side of the coil ... one goes to CDI, the other to the ballst unit, which, BTW, is just a resistive divider circuit with the tap going to the tach input.

[Early_S_Man]

One of the minor irritating flaws on those early color factory wiring diagrams is an occasional mistake in translation ... and the #10 'Switching SCR' on SL33 is one of those mistakes ... that is the Ballast Unit!

It has three wires ... one to ground, one to the tach, and one to the coil.

[Tspringer]

Thanks..... I gave up on getting the stock system to work. I had it wired correctly as far as I could tell, but no spark.

Now I have put $500 into a MSD 6AL with blast coil and such..... but apparently still no spark. Another thread.....


Terry