My truck had been running fine, until a couple of days ago. It started fine, all gauges reading normal (I'm a habitual and constant gauge-checker). I was out running errands, and after driving for a couple of miles, turned off the truck, and when I went to start it again, just got the "click." Well, I'd been having some issues with the neutral safety switch, but this felt like a battery issue. I checked the terminals, and the positive was a little loose, so I tightened it up, jumped it - it started right up - and after checking the gauges to make sure all was well went on my way. After a couple of miles, the engine shut off - as though you'd turned the key - and then popped right on again! (When it was off, all gauges were dead and so was the engine. It came back on - all the way, gauges and everything - within about a second.) I parked it, let it sit, and jumped it again. Same thing: Started right up, all systems go, only this time the lights, gauges, and everything but the engine shut down, with the engine finally dying after maybe another mile or so. Fine. Towed it home. Replaced the lead from battery to starter (it was a little worn), tried it again. This time I noticed that when the jumper cables are hooked up to the battery, the alternator gauge shows charging - and a little higher than usual, as I would expect. As soon as the jumper cables are disconnected, the alternator gauge shows zero (all other gauges showing appropriate levels), and the engine dies almost immediately.