My econoline 150 van has a 5.0 EFI motor the van will run and stall, I wait a few minutes and it sta...

My econoline 150 van has a 5.0 EFI motor the van will run and stall, I wait a few minutes and it starts and it will stall again even after changing the fuel filter what else could it be?

the vehicle is a Econoline 150 van conversion has a main and aux. fuel tanks, a 5.0L EFI engine, my wife was driving it and the thing just stalled out in the middle of an intersection, she waited a little while and started it and got it off the street and it died again. We got it home via a tow truck, I figured it was the fuel filter so I changed it it ran good the rest of the day, I had to use it the next day and it started to stall out again, I would wait a few min. and start it up and get it back to the house,  what else could be wrong.