Why is my truck not starting

Instead of throwing parts and money at it let's diagnose the problem! You need three things for the engine to run. Spark, fuel, and compression. So what's missing? 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. Possibly a bad fuel pump or fuel pump relay. If it won't run on the starting fluid check for spark. If you have spark and fuel but it still won't run it's time for a compression test. If all cylinders test very low or zero it's jumped timing. If you have no spark it's an ignition problem. Hope that helps! Jim