Here's a real stumper!

My 1994 Nissan pickup will start with a jumpstart, but not on it's own. Battery just tested good and fully charged. Alternator tested good. barrery posts freshly cleaned, clamps just changed (crimped and soldered). This one has me stumped, any ideas what could be wrong?

What about the wires to the starter? It could be your not getting enough power to the starter or have a bad starter.

Clutch interlock switch bad? There's also a relay (blue, I think) mounted near the inner front fender on the passenger side that sometimes goes bad.

When my '93 Hardbody did what you describe; turned out to be the ignition switch. Was an intermittent problem. Wouldn't start on the key about 70% of the time. Had to wire a starter button under the dash.