Ford: f-350 wont start without jumping solenoid, f 350, key switch

Question
my 1974 f-350 has the 390 v-8. It will only start if I jump
the fender mounted solenoid. I have changed the ignition
switch, and the solenoid but no luck yet. What should I do?
Thanks

Answer
pull the energizer wire from the solenoid, and with someone holding the key in the start position hook a multimeter to the end of the wire and to the ground. if you do not get voltage you most likely have a bad wire from the key switch, in which case you can by pass the ignition switch and run a push button starter, wired to the key. turn the key push the button engine starts. or trace the energizer wire back into the key switch with a multimeter and repair or replace the broken wire. if you take apart the harness and hold the key to the start position test each contact and find the one that is hot only in the start position, but not in the on position. run a new wire from there to the solenoid.