Explorer dies consistently, more so when fuel level decreases in tank, below 1/4 of tank. Tried changing out filter ( twice ) and pump, worked alright for a little bit, then problem returned.

sounds like a vapor lock problem , as fuel is pumped from the tank it has to be replaced with air from a vent tube , but then you should have an evap code ,scan for codes even if the light ain't on ,. the vehicle doesn't care if it's hot out

loosen the gas cap and see if it helps , you should defnietly get an evap code then , it might go away once you tighten it back up

I have a locking gas cap, installed it after replacing the fuel pump, because there was a whole bunch of sediment ( which appeared to be sand ), in the bottom of the tank. It does lock, but it's really loose, I'm sure the seal is not sufficient, but that was the only locking gas cap that fit my X, and I seriously need it locked in the event whoever dumped that sand in there, might try again !

scan for codes

Thanks, I'll try those, then get back ......