2001 Chevy Astro Van won't start at all!?

Start from square #1 Plug it in to a good scan tool to see that the ECM is communicating. remove the #1 spark plug, bring the engine up just before top dead center on the compression stroke - align the timing mark on the harmonic balancer by turning in the direction of rotation. Remove the distributor cap and look to see that the rotor is facing where the #1 spark plug wire is. Have someone rotate the engine wile you observe the direction of rotation. Set your firing order from there in the direction of rotation. Make sure that your timing chain has not jumped a cog by removing the valve cover that the #1 cylinder is on and confirming that both valves are closed. The intake valve should be just about to open with further rotation of the engine. It looks as if you may have altered your adjustment along the line. Your service manual will tell you how to set your crank sensor and re-set the distributor. You have to put the distributor in "field service mode" in order to set it. Did you test to see that you have correct power and ground to the coil? Are you getting ignition pulse at the coil? Were there any codes in the computer to start with? Someone here can help you if you provide in detail more info.