2002 GMC Sonoma Turns over but will not start

Well you need to determine whether it is a spark or a fuel problem first. Remove a plug wire from a plug and stick a screwdriver in the end and hold the screwdriver really close to the manifold. If you see a bright blue spark then its probably fuel. Next you can take starting fluid and spray some in the intake while someone turns the engine over. If the truck starts for a second and then dies(runs on the starting fluid) then it is a fuel problem. If it turns out to be a fuel problem you should then check to see if you can hear a buzzing sound from the tank when the key is turned.(This is the fuel pump) You also need to check the fuel pressure if you have the cpi(vortec engine) the pressure should be at least 56 psi