2002 Chevy Astro van won't stay on

If you're saying it cranks and won't start do below

Get a starting fluid/ether/better off gas in a spray bottle and spray into the carb or the throttle body on an EFI. Did it start and die? If not 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, distributor pick-up coil, ignition control module, ECM, Ignitor cam and crank sensors- Note: If it doesn't apply disregard it