The other day I was helping a friend move, and on my way my truck shut off and turned back on within a half second. When it turned back on the battery light was on. I took it back home, and left it running and checked the battery voltage. The battery voltage was only 12.2v. I figured it was a bad alternator, so I changed out the alternator and still the same thing. The only difference was the battery light wasn't on. The alternator never charged the batteries. The batteries are almost brand new not even a year old, so they're fine. They hold a charge etc. Fast forward to the next day, I go to try to run some tests and probe for voltages in various places and my truck won't start. white smoke coming out of the exhaust, and the tach only goes up to 100 rpm (it normally reads about 4-500 rpm while I'm cranking) So I go and buy a new cps from the ford dealership. replace that and the tach is still reading 100 rpm and still it won't start. All the fuses are fine, hpop is full, batteries are charged, oil level is full. what else could it be? It's a 2001 F250 6 speed.