02 oldsmobile silhoette van turns over but dont start

The elements needed for a running engine are: spark, air, fuel, and compression. Check for spark, the combustion engine is pretty simple. Plug one of the spark plugs back into its spark plug boot, and ground the body of the plug by placing the metal threaded portion against a metal part of the engine. Have a friend crank the engine with the key. Make sure there is no gasoline near the plug, and don’t hold the plug or wire with your hands. Just sit it down and watch. You should see a clear spark between the electrodes. If you don’t, then you have an electrical problem, also test cam and crank sensors. Check air filter for clogs...but unlikely
Also check for vacuum leaks or cracks in the air induction system. This could let in too much air and prevent the engine from starting. You can check for vacuum leaks by listening. And if your car fires at all, you can check for vacuum leaks by spraying a bit of starting fluid near suspected leak spots. See if the engine changes its tune. Be careful spraying that stuff near a hot engine, though.
Check fuel..Sometimes, if your engine isn’t getting enough fuel, the culprit could be your fuel pressure regulator, a fuel leak, a clogged fuel filter, or clogged injectors. But most of the time, it’s the fuel pump. The fuel pump can usually be checked fairly easily. First, identify your fuel pump location. The fuel pump and sending unit enter the tank from above, and can be accessed either via an access panel inside the car, from the front side of the tank, or they may require the removal of the gas tank. Don’t worry about removing the tank: the goal is just to get your ear as close to that fuel pump as possible...hope this helps..

Could be a number of things but cam or crankshaft sensor come to mind. Any codes???