'83 911sc cdi igntion issue...
 

Car will not start. CDI unit does not whine, whines intermittently with ignition key on. Voltage at pin 15 is +12.6V consistently with the ignition on and connector unplugged. The distributor coax cable ohms out at 622ohms at the connector plug pins. I did unplug the high-tension coil wire from the coil and installed a spark plug lead with a brand-new spark plug grounded to the engine with a clamp. There is spark but the color is an orange/yellow and not bright blue. I was surprised that it generates spark at all without the whine. Options are to send the CDI back to Specialized ECU for repair (where I got it originally and no longer under warranty) or opt for the new Classic Retrofit CDI+ unit or? There may be other issues, but the CDI unit is part of the problem?

I would say your CDI box is dead, or close
Save yourself a headache and purchase a MSD Street fire. East install and works great.

If no whine, then the CDI box is faulty. You can send it to a rebuilder (I recommend Bob Asholock), or replace it with the MSD, or use this as an opportunity to change the ignitions system to a 123 distributor or crank-fired coil-on-plug unit.

A bad test, not always reliable! So don't waste PP members' money without proper testing. "Or replace with MSD", laughable.

If you're going to make a recommendation, shouldn't you post this?

https://www.pelicanparts.com/More_Info/ATCDIREPAIR.htm?pn=AT-CDIREPAIR&SVSVSI=574&DID=59746

Why not allow Pelican Parts to benefit from its knowledge base, right?

Get back to me when you can show me an original Bosch CDI box that doesn't whine, but still works correctly. In the meantime, I have to go talk to a man about a horse.

Why send to Ashlock? Because he will test the unit first, and determine whether/what is bad. Then he will repair it. If it's still good, he will let you know that too. Nothing against PP.

What is your sample size, maybe one or two CDIs you've heard? Many exhibit no sound. Your naivety is laughable!

The key point is that PP most likely will NOT get the business!

Had well over 250+ Bosch CDI units through our shop.

Some are quieter than others but genuine 3 and 6 pin Bosch CDI units all squeal / whine when powered.

Easily audible with the ignition on prior to engine running.

(OP, Replica boxes or replacement internals tend not to make a noise)

Not really! Most likely with those that have loose cores/tape, the result of careless handling. Furthermore, it's also a function of one's hearing ability.
It's like many naive troubleshooting/guessing procedures of little value, another "wives tail" like multiple sparks provide more HP.

Another thread hijacked by Loren/Dave, who in the next 1-5 posts will recommend the OP sends it to System SC — his business in SoCal that he constantly recommends without disclosing the relationship.

Those 1-5 posts usually involve speaking poorly of competitors and arguing with others as the set up.

You noobies should read the rules. No ragging about other forum members. If you don't agree with something/someone, just move on. Loren is a valued long time forum member who has helped countless members over the last 20+ years, and I personallly have used his services many times with great results.

Read it back, I think he is the one throwing the stones ( "naive, laughable, wive's tale" ).

The guy is no doubt a capable EE , but the constant gaslighting is tiresome. The OP is looking for some basic help and Loren is just muddying the waters.

The noise is a function of the inverter (HV power supply) design - it oscillates at around 3kHz which is in the audible frequency range.

I've worked with these boxes for 15 years now and the only ones that are silent are broken.

End of.

No doubt Loren will be here to quote and gaslight some of my comments soon.

Too bad it turns this way. I always learn from threads like this with posts from knowledgeable people.

One question though, what's the component in the CDI that produces this sound? Is it a cap or the transformer that is acting like a transducer?

I guess it is kind of accidental, as the unit wasn't designed with this sound in mind, so there might be some functioning units that produce no sound at all. That is probably what Dave/Loren means. Sound is not systematic.

It’s the magnetic field in the transformer coils that cause them to vibrate and make the noise.

The coils are typically taped or glued to dampen the noise but it is still audible.

So there is truth in what Loren says - tape coming loose would make them louder. But they are not silent to start with.

Thanks. ;)

It's the magnetic ferrite cores that vibrate (noise) as the magnetic field changes, not the coils.

Actually, the tape around the cores is used to enhance the magnetic coupling (tighter) between the two cores.
This results in more energy being stored in the magnetic field to be transferred to the capacitor.
Sound is really of no concern, i.e. the CDI is in the engine compartment.

Elevenerife

The tachometer in my car (1983 911SC, UK spec) has become very erratic, usually works OK for 15 to 25 miles, then reads between nil and 4000rpm, when idling, drops back to zero rpm when on the move. I have had the tacho rebuilt and then checked and its ok. I have taken the CDI unit off (6 pin) and found that the metal strip that takes earth to the 31/1 terminal had burnt out. Surprisingly, the car was still running perfectly! I have soldered in a copper wire to replace the metal strip and hoped that would solve the problem but tacho is still erratic. Any ideas or should I just get a replacement cdi unit?

Loren is no longer around here. He (was) disappeared in 2012:

http://forums.pelicanparts.com/uploa...1756078953.jpg

He's been banned for more than 13 years due to "foul mouth syndrome" and severe gaps in the soft skills department. Wayne, the founder of Pelican Parts had to make a choice because customers threatened to take their business elsewhere as long as Loren was one PP providers of rebuild services and at the same time berating members....

It's still unclear how "Dave" is related to all this :rolleyes: :rolleyes: :rolleyes: