My Blazer wont start when it's cold or hot, it turns over fine and will start with starting fluid. when it does start up it runs perfectly, runs good with tons of power. what the heck would cause this?

 

I would start with the basics... Fuel/Air/Spark. Check the fuel pressure with a gauge. Your engine requires 55-60psi to start, but really only needs around 50psi to run. Air, probably not a problem. Spark, probably not either...