Hi 91 runner I heard you can run a jumper wire from 12v to starter to start

UNLESS you KNOW what you are applying voltage to , you might want to leave it alone!! Can be more dangerous than you think , if you get it wrong! Why not simply TEST for proper signal/voltage at the starter solenoid and main (large) wire that is the safest way to diagnose the cause of the problem. Have a helper turn the key when voltmeter is safely connected IF you don't get 12 volts from solenoid wire with key in 'crank' position --that is what you need to find out why not. IF you DO have good signal , then starter is most likely at fault.