My truck cranks but doesn't sart help?

maybe crankshaft position sensor ( sits between motor and tran and communicates with computer when it sees flywheel. That way computer an tell spark coil when to do it's thing. If any one of those components fail, it's dooms day ( no start)

Try spraying a little starting fluid down the throttle body. It should run a few seconds on that. If so it's a fuel problem. If not it's an ignition problem (no spark). But if you have spark and fuel but it still won't run it's time to do a compression test. If all cylinders test very low or zero it's jumped timing. Hope that helps! Jim