I have a 1997 chevy truck that one day driving back home it just shut down on me I ended up putting in a fuel pump and it did run for like 20 min and it shut down again and now I don't know what to do I had a friend put a computer to it and its not sending any bad codes it does run if I spray starter fluid but it won't start on its own

Need to change the oil pressure sensor located behind the distributor .Had the same problems .The sensor shuts off the fuel supply when it identify low oil pressure or when it malfunctions.wont show on code reader most of the time