Another engine cuts out question
 

Have a 68 911L 5spd. Engine runs great for about 30 min. then cuts out. Not a carb drible cut out. Instant dead. Usaually restarts after about 10-20 min. Just replaced, starter, alt., dist. (w/points), battery, dist. wires, voltage reg.. Perma Tune cdi box is about 6 years old.

Just noticed that the battery is about half charged at the time of the cut off.
Alt. is charging at 13.5.

My question is, could a faulty cdi cause the battery to drain enough to loose enough charge to affect the cdi itself. Or is it something else. Any input would be greatly appreciated.

I'm no expert on CDI's but since they typically "whine" all the time, I would think that's not the problem. I'd suspect it's something in the starting circuit that you just dealt with, as that is a source of large current draws. Your alternator/voltage regulator is working by the output you measured, but there is a huge draw somewhere. Someone will offer the testing methods of amperage draw for your circuits to help track down the problem. Meanwhile, don't drive as the continued strain on your alternator will soon kill it.

thanks Ossiblue, Seems the ign. switch could be the fault but will replace permatune with msd while I'm at it. Thanks again

likley the perma-doom. coud be a bad solder joint or the cap is going bad. the heat makes it act up. could also be the coil. i would replace with MSD cd and coil, unless the car is original, then i would find a bosch unit.

cd's can whine and still be bad, usually the capacitor in that case.

check the wiring from the dist to cd jsut to make sure it is good, those wires crack with age