1983 SC Dies Intermittently

[jcadwell]

I have a 1983 911 SC with a PermaTune ignition. I'm trying to decide whether the ignition is failing, or if I have another fault...

The car runs very well. It doesn't run rough, is easy to start, and idles well.

On occasion, usually after driving for a half hour or so, the car will die abruptly. Most, if not all, of the gauges immediately drop to zero, even if the engine is still being spun by the momentum of the car while it is in gear. This makes me think that it isn't a fuel problem. I'd expect the tach to continue working if the engine ran out of fuel.

Right after dieing, the car will turn over, but not give any indications of restarting. Cranking it over results in a fuel smell, but no ignition.

If I wait about five minutes, the car 'magically' returns to running fine, as if nothing ever happened.

I have a hunch that problem lies in the ignition box, but I'm not sure. I'd rather not give 400$ to MSD if that doesn't fix that problem.

I've searched the forums and read about a variety of relays that could overheat and function intermittently, but I'm unclear as to whether my car has them...

Any ideas?

[ischmitz]

Sounds like a bad Permatune - especially if the tach dies. Any other instruments that show an effect?

[jcadwell]

The oil pressure immediately drops to zero as well, and probably most of the other gauges. I'm not sure, because when it dies I'm usually in the middle of traffic and don't have time to study the dash while trying to get off the road...

[ischmitz]

bad ignition switch?

[jcadwell]

Is there a way to test for a bad ignition switch? It also seems like if the car won't start for several minutes, then abruptly does, that there is a time element involved. Does the ignition switch have any kind of relay that could be overheated?

[Kevin Saunders]

I had exactly the same problem with my 77 911S. I changed to a petronix system, installed a new rotor, distributer cap and plugs and have put a couple of thousand Kilometers on her and she has not missed a beat. Don't know for sure which component was the culprit but I suspect the rotor, it was a rev limiter type and I installed one of the same.

[Joe Bob]

They don't call them PermaCrap for nothing....intemitent issues can be grounds or loose junk in the component. One good thing about PremaCrap, they are potted and you can't fix a loose item. On the switch, thay CAN be opened up for inspection.

[James Brown]

Well, looks like a MSD customer soon!

[jcadwell]

Well, I can't change to Pertronix (not available for '83), but it sounds like the ignition seems to be the problem...

Any other ways to confirm?

[Bob Kontak]

I had EXACTLY the same symptoms. 81SC. Never found a way to confirm. Went through the Permatune website and trouble-shot lots of stuff. Green wire, ground quality, fuse connections, distributor pick-up resistance, coil resistance, etc. It's the Permatune box. Replace with a MSD 6AL and blaster coil (or whatever is the most current MSD combination). $300-ish and a long weekend and your troubles will be over. Absolutely no issues for me across six years.

Take your time and ground the box really, really well.

[jcadwell]

Thanks for one more confirmation. I took the plunge and bought the box... Did you replace the plug wires at the same time? I'm not in a position to spend another 150$ on "High Quality" wires at this point...

[Bob Kontak]

Nope - I would suggest one fix at a time.

Clewett makes a wonderful wire set at a relatively fair price.

How is your progress? Get yourself a multi-meter if you don't have one.

[jcadwell]

I replaced the Permatune with MSD, and after a little tuning, it runs great. I very much appreciate the help.