92 CHEVY BLAZER K1500 WON'T START

Our blazer will start if it's been sitting along time. But will cut of in about 15mins & not crank back up. We have had the following replaced: distributor, ignition module, coil, throttle position sensor, spark plugs, timing reset, fuel filter. When truck finally cuts off, it will crank but not turn over. My next quesses is that it the computer, fuel pump, o2 sensors, etc. Please help