1996 Ranger/stalling & won't restart for hours.

Happy Thanksgiving to all! This is a recent problem, just started a couple of weeks ago and has already cost me $400.00 for towing and diagnostics. Just bought this truck, used, a month ago.

1996/4.0/4 X 4/Auto trans./150,000 miles

1'st time stalled at stop light, level road. Short drive of 10 minutes, on a dry day about 65 degrees. Tested, within a couple of hours, fuel pressure gauge showed no movement. Fuel pump, you'd think.

However, started the next morning with no problem, Stopped and started it repeatedly, let it run, drove it, no problem for the next couple of days. Retested with fuel pressure gauge, showed 40 psi, pressure held during hour long idle, and held over night on cold engine and restart. Computer diagnostics shows no errors or problems on running engine.

Then, the next day (after 15 mile drive, full tank of gas), backing down the drive, truck stalled, again, wouldn't restart, for 2 hours.

Engine runs smooths and stall acts like "out of gas", when it does re-start, runs smooth, again. Doesn't seem to be any lose connections. Swapped relays between air conditioner and fuel pump (same model relay) made no difference. First stall was in 2 wheel drive/forward, 2'nd in 4 wheel/high reverse.

Figure this has to be an electronic component, but which one? Anyway to test the expected culprit for fault or failure?