SC won't start -- no spark

[TMoreken]

In my two years of ownership, my 911SC has never failed to start. Today, it happened. After parking the car this afternoon, I went out this evening to put her in the garage. The engine cranked strong and I could smell unburned fuel, but no start. I removed a plug and had my brother crank the engine. I'm not getting any spark.

What should I check first? CD box? Coil?

[jhawk1000]

Could certainly be a CD unit. My permatune went out and it did the same thing. It would not start after it got hot. Let it set for an hour or two and it would crank right up. If you need a CD unit, you will also have to replace the coil with a unit that is compatible. I bought my CD unit and Coil at Dart for a little over $400 for both instead of the $1576.00 Porsche wanted and about $200 for the coil.


Mel

[filou]

If you could check juice getting to the coil and CD. Start with fuse and go downstream on the electrical wiring. Do you have a tester (voltmeter) ???? I believe the car have a relay from ignition switch to juice of primary circuit of the ignition ???? i do not have my 911 Tech
ref book in front of me. Can you hear the CD box humming ????
Good luck and get discourage.
Let us know.
Filou.

[TMoreken]

Unfortunately, I do not own a Bentley Manual for the 911SC. What I'm looking for is a brief description or troubleshooting guide for a "no-spark" condition. I have a multimeter and can usually pinpoint these problems -- I've just never had an ignition problem in this car.

By the way, the cd box is humming and there is fuel in the tank.

[MY83SC]

CD is humming. That's a good sign. Lets hope that the coil is bad or the coil wire has gone south.

[MY83SC]

BTW. Did you pop off the distributor cap? My SC distributor bearings went bad and the rotor exploded. Too much play and the rotor sheared when in hit the cap contact points.

[TMoreken]

I just got home from work. I haven't had time to look at the distributor, but I had it rebuilt 6 months ago. I'm going to test for continuity on my coil wire and just check all the obvious stuff. Is there a resistence value for a good vs. bad coil?

[David]

Check that you have a signal coming out of the distributer from the green wire.

[Early_S_Man]

Todd,

In a CDI system, there is no power at the coil you can measure on a static basis!!! There are ~400 Volt pulses to the 'A' terminal of the coil when the CDI is triggered by the magnetic pickup coil in the distributor.

IMHO, you can forget coil and coil wire checks ... they seldom fail, if still the original black case Bosch coil! But, if it makes you feel good ... coil primary should be 0.4 Ohms - 0.6 Ohms, secondary should be 650 Ohms - 790 Ohms.

Pull 6-pin connector off the CDI unit and locate the green coax connections at Terninals #7 & #31d. Check with multimeter for 600 Ohms +/- 10% at room temperature. Next, pull the fuel pump relay, and while cranking engine ... check for an AC Voltage of around 2 - 3 Volts at the end of the green coax, at Terminals #7 & 31d.

Here is a colored version of the wiring diagram with the ignition circuit interconnections:

[TMoreken]

Finallly had time to troubleshoot my ignition problem. Just for the hell of it, I first jumped in the car and tried to start it. It started on the second crank! I drove the car 100 miles this weekend with no problems. Thanks to everyone who chipped in with information. I'm guessing something was heat soaked, but it's a little unnerving to not know what it was.

[no substitute]

Are you running the factory CD box?

[Early_S_Man]

Todd,

I forgot to mention in my original post that if the green coax is discolored brown, or cracking and frayed ... it needs to be replaced! They have been known to cause intermittent problems with stalling, missing, or occasional 'non start' conditions! It is only around $30 from Pelican, and gives great peace of mind after replacement!

[TMoreken]

My entire ignition system is factory OE.

I had some relatives staying at Hilton Head Island and the idea of checking continuity on 24-year-old frail wires vs. playing 18 holes was not a hard decision to make. I will check the green co-ax and double-check all my connections.

It's been my experience that these problems will "re-appear" at the worst possible moment -- i.e. the end of a great date or out in the middle of the stix where all the locals think "you got a purdy mouth, boy!"

[jhawk1000]

Just an update on my problem where the 1980 SC Targa I own would run okay when cold but when it warmed up, it would die and not start for an hour or two. I first of all had some work on the Cat converter. Did not help! Got and new fuel filter and flushed the gas tank. No help! Finally installed a new Permatune CD and Permatune coil. Problem solved!!!!!

It runs great now.

Mel

[no substitute]

Originally posted by jhawk1000
Just an update on my problem where the 1980 SC Targa I own would run okay when cold but when it warmed up, it would die and not start for an hour or two. I first of all had some work on the Cat converter. Did not help! Got and new fuel filter and flushed the gas tank. No help! Finally installed a new Permatune CD and Permatune coil. Problem solved!!!!!

It runs great now.

Mel

Hmmmm...

[jhawk1000]

I probably ought to tell you how the mechanic found it. I would drive it in and he would work on it and it would start right up. After purging the gas tank and changing the fuel filter, he let it idle for about an hour. It died and then he checked the spark---none. He felt the Permatune and it was scalding hot. He iced the Permatune down and it started again so he called Porsche and they said that it did happen from time to time that the Permatune got hot and just shut everything down. Since then, with the catalyst work, the blower into the heat exchanger, new hoses and fresh gas, the car actually runs better than it has for years and I have had it since new. It has 115,000 actual miles, has the updates and I have now replaced the rear seats with new leather ones, new tires, new carpet, and still is bright and shiny as new. Oh yeah, bought a mint targa top off of ebay for the ridiculous sum of $300.00 so it is my fun car again.

Mel

[Paulporsche]

Mel,

Congrats and thx for the update.

[no substitute]

Just curious, the CD that you replaced with a Permatune was also a Permatune and not Bosch? Thanks.

[jhawk1000]

Yes, it was a Permatune CD and not Bosch.

Mel