David_A

I installed a Pertronix Ignitor in my 74 911 and at first, wired it incorrectly. Now I have it wired correctly but it will not start. I have bench tested the distributor with the ignitor installed and it tests good. I have also replaced the coil with a Pertronix Flamethrower 3 ohm model. I am afraid I've damaged the CD unit. I don't know how to test the Bosch unit. If I have to replace it, I've read that the MSD CD unit is good. Has anyone used these or has any advice? I can have my Bosch unit rebuilt if that is best. Any advice will be most appreciated.

theiceman

i am not familiar with this but it does come up fairly often so do a search, there may be some good reading in here , you just have to find it . i think there even may be a post by Loren on how to check your CD unit. Every time I hear mine whine louder than my wife, i know it is good ..

David_A

I'll let you know if I come up with a solution.

Lorenfb

I don't know how to test the Bosch unit. If I have to replace it, I've read that the MSD CD unit is good."

Testing the Bosch CDI (3 pin):

1. Check for a good 12 volts at the center pin (unit should buzz with key 'on'),
2. Use a test light (connected to 12 volts) to check for a good ground when
the points close,
3. Remove the coil wire from the distributor and place about 10 -15 mm
from alt. fan housing,
4. Crank the engine and test light should flash and sparks should occur.

Avoid those silver coils. Use the original small black or the Bosch blue coil.

Avoid converting to the MSD unit as there's no advantage over the Bosch unit,
and the MSD given its complexity is less reliable besides having to make
installation changes.

theiceman

My silver coil lasted a whoping 120 minutes .. when it died I put my 30+ year old coil back in and it has been running ever since.

David_A

Thanks Loren, I'll try taking your advice. My Bosch unit is not making any noise so I suspect it's fried. I'll look into a rebuilt Bosch.

David