1988 Chevy Truck Truck won't start & when it does it on

welcome, you need to use a gage and check actual fuel pressure. Some throttle-bodies have an internal pressure bleed off circuit, meaning, when the pump stops the pressure may bleed off, normal on some systems. Are there any codes? You can check them yourself.

Hi there bgriffin02 and TY for the donation this is what keeps the site going

Lets start by ensuring that the fuel pumps are producing the correct fuel pressures, the fuel pressure regulator is controlling the fuel pressure -if okay inspect and clean out the idle air control valve and test the TPS and MAP sensors. Other possibilities could be a bad ignition switch and a defective coil, distributor pick-up coil, ignition control module

Next time it dies out try doing below don't wait or cycle the key to determine if its a fuel or spark related problem

Disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor /distributor pick-up coil, ignition control module, ECM,Ignitor camshaft and crankshaft sensors- Note: If it doesn't apply disregard it