Originally Posted by rmvespa
One more piece of information, both times the trucks stalled it was after being refueled (ran fine for miles after refueling), and wife was in passenger seat. I'm thinking she may have bumped the inertia switch connection???
Sometimes, an inertia switch can intermittently go open even if it doesn't fully trip. This can become more common as the miles accumulate.
Given the fact that the mechanic got it to start by messing with the IS and that there was a passenger present both times, the odds are that the problem is related to the switch.
First I'd check to be make sure that the connector is fully seated and snapped in. I had a Windstar go belly up and it was because the harness connector was only resting on top of the pins of the Inertia Switch. It ran like that, relying only on gravity, for over 30,000 miles from new before refusing to start.
If the connector seems OK, I'd try pounding a fist on the floor of the PS footwell with it idling to see if the engine dies. Even if nothing is found, I think I'd spring for a new one. As I recall, the switch is not that expensive and no one likes to be stranded.