911SC no spark
 

It died in my garage when I was moving it out of the way. It ran, it died, it would not restart. Checking with a timing light and with a spark detector revealed no spark. Fuel comes on when the air metering plate is lifted.

All specs are lifted from previous Pelican threads.

Black Bosch coil tests 1.2 ohms primary (should be 0.6-0.9, out of spec), 680 ohms secondary (650-790, in spec). Replaced with second black Bosch coil in spec, no change.

Resistance between poles 7 and 31d on the 6-pin CDI connector ~600 ohms, in spec. I think this is the green wire, yes?

AC voltage between poles 7 and 31d climbs to ~1V on cranking with fuel pump relay disconnected. Out of spec (should be ~3 volts).

CDI unit is the Classic Retrofit CDI+. The tach needle completes its sweep when key is turned on, so it has power. Substituting Bosch CDI did not solve the problem.

Ideas? What next?

check for spark at the coil's high-tension lead and then at the spark plugs. Remove one of the plug wires and grab a known good spark plug and hold to a good ground. If no spark, inspect the distributor rotor and cap for wear or damage. Check for proper power and ground to the CDI unit and coil.

Cap and rotor new 200 miles ago, and still look new.

No spark at the coil, no spark at the spark plug.

11.9V between pins 15 and 31/1 (system power for CDI unit)

67Ω between 31/1 and engine mount bolt head (system ground).

Seems like a CDI problem.

I suspect the green wire from the dizzy to the CDI. They get baked and the insulation cracks.

Except the wire's resistance checks in spec and it produces its desired 1V AC on cranking. It connects to terminals 7 and 31d on the CDI connector. Could it still be the problem if it meets those criteria?

I can only speed for a Bosch CDI box. I assume it makes its distinct whine when powered.

With a spark plug hooked up directly to the coil output and grounded it needs to produce a spark assuming your trigger signal is present during cranking. If not the CDI box needs repair or the coil is no good.

CDI Loaner…….
 

Dru,

Are you now back in USA? Last time we communicated you were stationed in Germany. If you need a good CDI to use for your troubleshooting, I could lend you one and send it back to me later. Or send your CDI to either Ingo or Bob A. for evaluation.

Tony

There's another source that's been repairing CDIs for Porsche dealers/independents, and Porsche owners, for 35+ years with a 5 year warranty, systemsc.com.
Some still remember they were the Pelican Parts only CDI repair source. They indicate over 10% of their present Porsche electronics repair comes from Pelican members,
not only CDIs.
Furthermore, they are on the Porsche "Preferred Vendor" list.

yup - some might even remember when Wayne had to ban you because people threatened to boycott Pelican Parts with you insulting others as LorenFB :rolleyes:

Dave (Loren),

I intentionally did not include Systemsc.com because I knew you would jump in and recommend your company.

Tony

Tony,

We moved back to the US about 2 years ago and are now in Kentucky.

I'd love to try a loaner CDI box, as everything else seems to check out OK. I will send you a PM.

And I have a backup CDI box that I will get evaluated as well.

Thanks!

Ingo,

The CDI+ does a nifty tach sweep to let you know it has power. No loud whine, though. I kind of miss it, but enjoy the reliability.

Regarding the trigger signal, Jonny at Classic Retrofit has been going through this with me and he pointed out the CDI+ has a green LED beneath the top mounting bolt that flashes with signal. I have signal.

As mentioned above, Jonny at Classic Retrofit responded to my customer support request and has been troubleshooting with me. Turns out that the CDI+ has a signal LED at the top of the box (it's inside, but you can see the light shining through a small hole). that confirms signal from the distributor. Given that I had signal, he said it must be "on the output side," that is the coil, the distributor, or the plugs.

So, commence coil exchange.

http://forums.pelicanparts.com/uploa...1755275383.jpg

The two black Bosch coils measure in spec, the black 123ignition coil is not in Porsche spec but is close and came out of the car I drove today (known to work), and the silver and blue coils have out-of-spec secondary resistances. Not sure they would work or not, but it turns out not to matter.

Say, what's this behind the coil?

http://forums.pelicanparts.com/uploa...1755275383.jpg

This just might be the problem.

The shielding is hard as a rock. Not sure how severed the copper is, but the wire insulation is still pliable. Once I cool down, I'll go back out and see what I can do with this.

In all the troubleshooting guides I've read, I don't remember ever seeing "Check that the coil is getting power."

Looks like you found your issue, good job

The coil doesn't get "power", it gets a spark pulse - less than a millisecond.

http://forums.pelicanparts.com/uploa...1755282872.jpg

If the two leads shorted at the bad insulation, the CDI may have been damaged.

Well that's not good news.

Perhaps a prompt to check continuity of the coil leads with the 6 pin connector.

Dave,

Given how you treat people here, unless I had no other choice I wouldn't consider doing business with you.

I guess you don't follow my many posts, where posts are just to provide PP Forum help on many Porsche topics. I don't see much from you!

I help everyone, even ones like you! I'm sure systemsc.com, given their CDI repair volume, really couldn't care less for an insignificant $250 CDI repair order.
Furthermore, they don't repair the Classic Retrofit CDI+.

Consider searching the Forum about how CDIs function, it'll be helpful in your present troubleshooting.

Interesting that you quote my help (post 16), but make negative comments subsequently;

http://forums.pelicanparts.com/uploa...1755296186.jpg

Thank you, Dave.