I have a 2004 monte carlo SS, i replaced the MAP sensor due to a code for it and cranking problem. it fixed it for a day then now it will only start with carb spray and will stay running on its own. i replaced fuel pump a month ago due to 16 psi when running. i checked the injector with a noid light and didnt have a pulse but have 55 psi fuel pressure and spark. used a volt meter to check if i have power front injector power wire and have 12 volts. any sugestions?

 

Try the ignition control module. I had mine go bad last year at 130k miles, had the same issue. Crank no start. you can find instructions on how to do so here
https://easyautodiagnostics.com/gm/3...-sensor-test-1

Other issue could be a bad coil, but it's like the ICM if cranking no start with no pulse