Mr Paul [T-28]

If anybody can help me out, my father and I would appreciate it. Tonight his Porsche quit running, here are the symptoms. While he was driving the tachometer was going crazy. It was going between 0 and 7000 RPM. Just before he shut it down, the windows and sun roof were closing very slowly as if it didn't have enough battery power. Fearing that the battery was dead, he turned it off and was unable to restart it (acted like there was no battery power). He came back 2 hours later and it started right up and he drove for about 3 miles and it died again. He let it sit for a while and then tried to restart it again. It would turn over, but never fire. They then attempted to jump start but to no avail. What does this sound like to you guys. Bad electrical connection, alternator, battery.
Thanks.

Mr Paul [T-28]

BTW, it back fired just before it died for the last time.

Kris Hansen

Probably a bad alternator/generator which wreaks havoc on the electrical system..

s_wilwerding

I owned a 1981 911SC. In answer to your question, the 911SC is fuel injected - it uses a mechanical system called CIS, continuous injection system. It sounds like your father's problem could be an alternator or the voltage regulator. Have him (or someone), if they can get the car running, test the voltage going to the battery. If it's above 14V, the voltage regulator is likely bad. If it's below about 11V, it's probably the alternator on the way out.

It may also be some other electrical problem, like bad plug wires. When an engine isn't running, 95% of the time it's either gas or spark. If you've got gas, then I would say it's something wrong with the electrical system.

Mr Paul [T-28]

Thank you Kris and s_wilwerding, that is the exact info that I was looking for.