1993 Chevy Suburban Starter

Starter solenoid could be sticking or a faulty ignition switch.

The power comes from the ignition switch thru the NSS and then to starter. The NSS has power only when the ignition switch is in the cranking positon-If you hook up the starter correctly-your problem is the ignition switch-

How many small terminals do you have on the starter if you have 2 switch it around and see what happens.

The purple wire goes to the S terminal the other wire goes on the R which is the ignition by pass if it continues to crank -the solenoid is shorting out if not were right back to the ignition switch.