Chevrolet Repair: 1988 ck 1500 4x4, fuel pump relay, vacuum leak

Question
fuel injectors will not function (tbi)
fuel pump , fuel filter , rebuilt dis , fuel pump relay , ecm , have all been replaced . have good spark , good fuel pressure , have replace dis and ran good for a while. now it wiil start and run till you shut it off then will start for a day or two then it may start then it may not. all grounds ok all wiring to ecm ok  

Answer
Good fuel pressure is 13 to 14 PSI, engine running or off.
No guessing...test it.

If the egr happens to stick open on some carbon, it is a large vacuum leak, and would be hard to start.

Have you checked the injectors with "noid" lights? They may be operating, but low fuel pressure will not work.

Van