91 Lumina 3.1 Keeps Dying

I have a 91 Lumina Car 3.1 it keeps on dying on me at weird time for the most part it starts right back up but sometimes it just cranks and cranks and if you let it set for a while it starts up. things ive done to it so far have been tested the fuel pump, changed the fuel pump, changed the coil packs and control module, changed the computer,changed the crank censor,put on a new oil sending unit. When it dies i'm still getting spark and i'm getting fuel to the fuel rail i have an ideathat it may be shutting down the injectors but i have no way of testing them any help would be greatly appretiated...

i had a problem like that on my 95 t bird v8... same problem you described... it ended up being the crank position sensor, which on the bird was behind the ac compressor, its nothing more then a little magnit with one wire that goes to it, and all it does is sense the position of the crank to know what plug to fire first when you crank the car (well at least to my understanding) the part if i remember correctly was 10 bucks or so (give or take).