Check out my post
928 Oil Pressure Sender Dead after 15 Minutes? - the main starter wire is on pin 14 of the 14 pin plug. From there it goes to the starter itself. You can verify that whole circuit up to the starter is good by carefully putting a voltmeter from '50' ( heavy gauge yellow) on the starter to chassis, and checking for 12v when you turn the key. If it is missing, carefully pull the 14 pin plug ( disconnect the battery first) then put you meter between pin 14 in the socket and chassis, reconnect battery and repeat. If it is missing at pin 14 you have to work back up the chain, if it is there at pin 14 and not at the starter then wire to the starter is probably broken.