truck won't start

I'd check for multiple issues. With engine cranking check spark at the spark plugs where applicable. If spark everywhere us a gage and check proper fuel pressure. Check fuel injector pulse. If your missing all three check for rpm signal, that signal usually comes from crank sensor. Make sure battery has a full charge. Don't replace anything unless your testing points in that direction. Can you check for applicable trouble codes? If problem only on one system, have to check component and wiring on that system.

If u don't have fuel gauge to test fuel pressure, try spraying quick start in the intake throttle body to see if it's fuel related