2003 GMC C2500 Duramax won't start

Do below and get back asap with some testing results

Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 in away from ground have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs, coil's resistances, cap and rotor /distributor pick-up coil, ignition control module, ECM, Ignitor camshaft and crankshaft sensors and computer. Note: If it doesn't apply disregard it

Check and test the glow plugs and injection pump