had it tested had low fuel pressure changed fuel pump wont start getting fuel and spark and air what else could it be ?
flooded, hold to floor,crank, a shot of start fluid first helps,just one second shot then crank
Can't add to Jimmy's response but it might help to know what year, make, motor, etc.
it is a 1998 gmc sierra has a 5.7 motor
Is it a vortec? And if so did you try starting fluid in it? If both answers is yes and it backfired thru intake you are probably looking at replacing the intake. Vortec intakes are plastic and are not made to withstand a backfire.