82 SC - No spark issue

Brudock · 06-21-2015, 07:28 AM

Hey everyone,

Looking for some support from fellow 911 owners. Just bought my first 911 about 3 weeks ago, drove it back home and it died on the highway about 1 hour in the drive. Looked like it was starving for fuel and it would only restart once it had cooled down. Everything led me to believe it was the fuel accumulator which I've just replaced.

Now it won't even try to spark. I think I've narrowed it down to the Bosch 6-Pin CDI. It does the high pitch sound but I think it's not sending any spark to the coil.

Here's what I tested:
- Coil, it's within spec
- Green wire going to the distributor, it's within spec
- CDI pitch sound, it does it.

Here's what I need to test
- Pin 15 on the CDI, make sure it's within spec
- AC Voltage on pins 3-6 while cranking

Now my question, I'm located in Montreal, Canada. Is anyone in that region with a spare working 6-Pin CDI so I could test to make sur that this is my issue before buying a new one or converting to MSD?

Much appreciated!

Brudock · 06-21-2015, 08:54 AM

Since pics are mandatory, here's one! In all her glory on a flatbed!

I've just tested voltage on Pin 15 of the CDI, it's good, same with AC voltage between Pin 3-6 while cranking.

Really sounds like a broken CDI unit

tirwin · tirwin's Garage

if you have a Bosch CDI and you hear the high-pitched whine then that just means it hasn't obviously failed. It is very common for them to work until they get hot, then fail and work again once they cool off.

Your best bet is to find a local person with a known good CDI that is willing to swap to test. If that solves the problem you found the culprit. Otherwise you should troubleshoot everything else and rule those things out before considering getting the original rebuilt or replacing with a different CDI. There are several different aftermarket CDIs available. I switched to MSD Streetfire because the box + coil is about $120. There are a couple of things you need to do to to make it work. I just saw a new company marketing a complete drop-in that looks exactly like the old Bosch with modern features. No experience with that one myself but it looked interesting. The point is there are plenty of good choices should you decide to go that route.

This is a fairly common issue. Lots of previous threads exactly like this one. Most of the time it is either the CDI, coil or fuel pump.

timmy2 · timmy2's Garage

Fuel Pump Relay is notorious for failing, swap it with a Black one and see if it runs.
If the relay seems loose spread the contacts with a razor blade.

kjchristopher · kjchristopher's Garage

Quote:

Originally Posted by Brudock

Now it won't even try to spark. I think I've narrowed it down to the Bosch 6-Pin CDI. It does the high pitch sound but I think it's not sending any spark to the coil.

I had a similar failure two years ago - high-pitched noise but no spark. That kept me from looking at it for a while, but when I got to it and did the trouble shooting procedures (can't recall if I found them here on Pelican or in the Bentley manual) it tested out bad. Replaced and haven't had the issue recur.

Jonny H · 06-21-2015, 03:22 PM

The high pitched noise is the 360V power supply inverter. Having that noise is better than not, but it doesn't mean the box is 100%. You can still have a problem with the input trigger or the switching circuit.

We have a upgraded replacement box launching soon. See www.classicretrofit.com

timmy2 · timmy2's Garage

Determine if it is a spark or a fuel delivery failure before replacing parts,
For Spark:
Pull the red fuel pump relay and pull a spark plug wire when it fails and see if you get spark using a spare spark plug by grounding the electrode to the case while cranking.
Important: Use a tool to insulate yourself from the spark plug and wire!

For Fuel:
Reinstall the red relay and then with ignition on, lift the air metering lever in the airbox for a couple of seconds and you should hear the injectors make a squealing sound. (Don't do it too long as they are dumping fuel into your cylinders!

Brudock · 06-22-2015, 03:54 PM

Thanks for you replies guys.

It's definitely a spark issue. I've isolated it to the CDI box but I'd like to test another one before purchasing a restored or an MSD box.

@kjchristopher: I've seen some videos to test it, but it seems tricky (https://www.youtube.com/watch?v=N9zJXqhIiVo) do you recall part of the procedure?

@Jonny H: Fairly sure the trigger is never made anymore. Any price estimation for the module? You're looking for reviewers?

Anyone in the Montreal, Canada area that could help me? Cannot wait to drive the car!