No start issues
 

I have a ‘71 911T that is giving me starter issues. Pulled the starter and had it checked and the selonoid was bad so I replaced with new starter. Worked great for half a day and now again car will not start. When I turn the key to the start position, power is being pulled because I can hear the fuel pump bog down. If I cross the terminals on the starter, cranks over hard. So, unless that selonoid is bad (haven’t had a chance to pull it and test it) I am guessing it is the switch. My question is how to trouble shoot the starter switch. Can I cross the 30 terminal to the 50 terminal on the plug? Or is there another way to test to determine whether switch or starter? Thanks

It's probably a dirty ground wire from the trans to the body located at the forward part of the transmission.

A good troubleshooting technique for a 914, but can also be used on the 911:https://www.pelicanparts.com/techarticles/mult_starter_diag/mult_starter_diag.htm

Edit - they do have troubleshooting for the 911 that includes the ignition switch:
https://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/87-Starter_Troubleshoot/87-Starter_Troubleshoot.htm