On your marks, get set...
 

and nothing.

Starter problem - searched archive but nothing seemed to give any direction.

Three times over the last 6 months my starter has let me down. Good battery, power getting through and ground good. Turn key and nothing happens. Give the starter a little tap (used to do this to my Mini) and the starter works fine. On its way out or just needs servicing? Why does tapping it work?

Check your ground strap...again! But there seems to have always been a heat related problem with the early 911 starters...

The solenoid (small cylinder attached to the starter) is filthy inside, and having a difficult time operating as a result. You can remove and disassemble the starter, clean and reassemble and it will probably work fine for a time. Months, maybe years.

You can remove the starter and take it to a local electric motor repair shop. rebuilds are about $100, and you should end up with a starter that is the equivalent of a new starter.

buy a new one.

Buy a rebuilt one.

Those are your options.

What Super & Paul said. I had the same problem with my starter in my SC.