Ok ill try to make this as short possible, i went to start my 01 Blazer yesterday and it acted like it didnt want to start but did after a second try. Then last night it would not start at all. I can hear the fuel pump kicking on, and the engine will turn over but just will not crank. After a few attempts my battery was dead, i hooked a charger up to my truck and it started. Soooo i had my battery tested, it failed and i replaced it. The truck started again but ran rough at first, also whenever i go above 3,000 rpms it feels like it doesnt have any power. This morning i tried starting it again and im back to where i started, it turns over but will not crank. Any advice from you guys is GREATLY appreciated.

 

I'll beat the moderators to the punch this time, and mention the "96+ Fuel System Diagnostic" that appears at the top of this forum. It works pretty well, but you'll need a fuel pressure gauge to follow some of the steps. In all likelihood, you'll also want a dependable - but not an expensive - VOM at some point. $12.00 will buy you all the VOM you'll need.
I'll also mention that you will read a lot of stories here about failed fuel pumps and dropping gas tanks. Frankly, you might want to get yourself psyched up for an afternoon's worth of work in that regard.
That you have little power at higher RPM (not rpms; the term is already plural - revolutions per minute) is a familiar refrain when fuel pumps were eventually replaced, but that isn't the only possible cause. Also, fuel pumps can "run" and still have insufficient power to generate the necessary fuel pressure these engines need.
I've just gone through an extensive and lengthy fuel system failure and repair proccess, so I'll help out where I can.