TROUBLESHOOTING
Starting System (Vehicle in a safe condition)
A) Test the starter motor and solenoid: Connect a jumper from the Hot battery post of the solenoid to the "S" post of the solenoid.
B) ^^ as above Determine whether the ignition override switch (i.e. Starting safety switch) are functioning correctly, Disconnect and jumper the connector if needed.
C) Check the ignition switch "START" position: Connect a 12 volt test lamp or voltmeter between the starter (S) post on the solenoid and ground, turn key (Switch) to start and verify voltage presence at the solenoid post.
These should be a few good diagnosis step to start (no pun intended) with.
JIM