5.0L Vortec - 96 Express, Stalled while driving - started right up - passed off as a fluke. Next day, under a towing load, check engine light (haven't had time to get code yet), then another stall - hard to start back up this time. Got it started and completed my chore, then parked until I have time to look at it. Noticed fuel gauge bouncing. Fuel pump supposidly (didn't get old part back) replaced about 2 1/2 yrs ago and 42K miles ago.

Sounds like it's not getting fuel. Check fuel pressure at the fuel rail. If low, make sure the pump is running. If the pump is running, but no pressure at the rail, check fuel, filter. Get back to us with result of these checks.

First place I would check are the battery terminals. Remove them and clean the posts, re-attach and tighten them. You can buy a tool for cleaning the posts at your local auto store.

Auto Zone does not test the alternator under full load so the test result could be borderline.
start the car and turn everything on. If the voltage drops lower than 14.2
replace the alternator.
also the battery could be being drained overnight. to check use a test light by removing a battery terminal and connecting light between battery and cable with car off.
if it lights start be removing fuses.
when the light goes off the problem is with this circuit.
lastly if the light stays on take the wires off the alternator.
if the light goes out replace alternator.

Sounds like your car just stalled out. I wouldn't be too worried about it unless it starts to happen often or if any dash light stay on. Scott

I chased a similar problem for several years. Stalled, got towed no problem found. The thing would heal and then fail at random on hot days. After checking everything electrical, fuel pump pressure etc, nothing could be found and I could not duplicate the problem. One day after being towed to a shop again, van started and would not fail but this time I had the mechanic put a clear by pass line along with a pressure gauge and I monitored the flow for about forty five minutes. Suddenly I started to see a stream of air bubbles and the pressure began to drop until the engine shut off. It was the FUEL PUMP all along and no one was able to determine that w/ all the test equipment. Went to Kragen Auto, now Oriely's and got a fuel pump. Had the shop drop the tank and install it. Have never had a problem again. Don't worry about what the mechanics tell you that it is not. Change the fuel pump

does sound like a fuel pump

remove dog house locate test port and install guage should be 45-60 psi

check the filter! first! it is possible its stopped up! when taking the filter lose start at the rear line and check to see how much pressure comes out? if its little to no! pressure then the fuel pump is weak!

If the scan will narrow down which o2 sensor it is and replace it. If it has more than one on that year that is. Under load you will probable have a richer fuel mix. If the sensor is going going bad it may only get out of spec reading under heavy load and warmer temps. I have had similar issues with GM and it was easily fixed.

Maybe the accelerator needs to be reset. My friend had a Nissan Murano which had similar symptoms. His friend from Nissan did a combination of key-starts to reset the computer.