hello all. im a newbie here. purchased my 1972 vintage 911 three months ago and love it. not my daily driver, but a weekend run about.

however, i have been having some technical problems. visited two porsche service centers near my area and they could not figure this out.

car run great. but after driving about 20-30 minutes, engine just shuts off. i can crank it, but will not fire back up. need to let i cool down about 10-15 minutes, then up and running again like nothing happened. i have had a complete tune up and no machenical problems were found. WHAT THE HELL COULD IT BE??? my mechanic could not figure it out, and niether can i.

if anyone has info and can help me it would be greatly appreciated. thanks.

 

Hard to beleive trained mechanics could not track this down but...... Bottom line is it has to be fuel or electric. Next time it quits pull a plug wire and see if you still have spark. If not I'd look to the CDI. If you have spark check the fuel delivery. Could be a line plugging under pressure that clears when the pressure disapates. Also the fuel pump may be locking up. Had that problem with a race car once. It would just quit out on the track, but by the time it was back in the pits it would start right up. The pump cooled enough on the tow back to start working again. Found it by accident when the switches were left on and all of a sudden the pump just stopped.

 

This should not be that difficult to trouble shoot. During the 10-15 minutes where it is not running, pull a plug and see if it is firing. This problem sounds electrical. If it is not firing it is most likely the coil. However, I have seen this situation with a fuel filter that stops up after a few minutes of run time. If the car stops dead, it is most likely electrical. If it stumbles before shut off, it is most likely fuel. Either way, this should be simple to diagnose.
Tim