Trying to search for threads on 3-wire CDI faultfinding

Gav P · 01-20-2009, 03:51 AM

G'day,

My 73 2.4E engine died mid-journey the other day, and I suspect the CDI box may have blown. I've been trying to search pelican for threads on this, but unfortunately the search engine on this forum doesn't seem to respond to the term "CDI"!!

Pretty frustrating. However, so far I've still found quite a bit of detailed stuff, e.g.

History of Bosch CDI ... toubleshooting info, parts list changes, and schematics ...

However, I'm no electronics guru, so this is a little too deep for my knowledge level...

Can anyone recommend a quick in-situ method of determining whether the CDI (or coil for that matter) is working? I do not currently have a replacement coil or CDI to swap in, but I do have multimeter, test lamp etc etc..

Also, if you have more luck than me with the forum search term "cdi" then please let me know how!

Cheers for now,
Gavin

T77911S · 01-20-2009, 04:46 AM

my guess is CDI is too short. I tried a search for "915", i was looking for a tranny i saw for sale, it came back "sorry no match found"

i had a 914 with a 2.2E in it. i bypassed the CD unit and made it run like a conventional points/coil ignition system, my permatune was bad.
i tried to make my 77 run this way when i suspected once again a bad permatune. it would not run in the points/coil mode, i ended up replacing the coil after i put in a new MSD. maybe i should try the old points/coil system and see if it works now, would be a good limp home mode, although i carry a spare CD and coil.

LuftWaffle · 01-20-2009, 05:19 AM

Hi Gavin,

From none other than Warren:

Bosch 3-Pin

Best of luck!

John

Gav P · 01-20-2009, 08:38 AM

Cheers guys, yep you're right the search engine doesn't like "cdi" these days becuase it's too short apparently... but a little bit of lateral thinking goes a long way - thanks John

Once I've nailed the problem, my aim is not to drive anywhere without a spare CDI or coil from this point on! Lesson learnt

HarryD · 01-20-2009, 08:11 PM

Quote:

Originally Posted by Gav P

Cheers guys, yep you're right the search engine doesn't like "cdi" these days becuase it's too short apparently... but a little bit of lateral thinking goes a long way - thanks John

Once I've nailed the problem, my aim is not to drive anywhere without a spare CDI or coil from this point on! Lesson learnt

Hi Gav:

Welcome to the best Porsche BBS on earth. I personally think that the '73 911's are the top of the heap. And while I think the CIS T is great car, your E is definately way up ther on the cool scale. How about a picture?

If you car has points, it can very likely be the culprit.

Try this thread for some things to try. How do i check a coil with a timing light??

When searching for advice on electronic items, look for posts by early_s_man.

ischmitz · ischmitz's Garage

Gavin,

a 3-pin box can be tested fairly simply; remove the 3-pin connector and run individual wires to it. Pin B (center) is +12 volts, Run a wire from pin A to the coil (the other side is GND) and then hook a wire to pin C. Connect a spark plug to the output wire of the coil via a high voltage cable and ground the spark plug.

Once you provide +12 volts to pin B of the box you should hear the 3kHz whining noise. Once you touch the wire from pin C to GND you should see a spark being generated.

Ingo

Gav P · 01-21-2009, 01:29 PM

That's perfect Ingo, just what I need. I'll give that method a go just as soon as I get some time in the garage this week

Harry - thanks for the interest, here's a sorry pic from when the ignition died on me! -

But also, one from last year, during the car's one and only time on a track.. fun times