2000 Blazer won't turn over with out pressing throttle

I don't know too much about problem diagnosis so this maybe an easy one...

2000 Blazer. It won't turn over unless I pump the gas. Just started all of the sudden and it cranks for about 5 seconds prior to starting even when giving it gas. I am not having any other issues. My gas mileage is about the same. My power is fine and I am not droping rpm's at any point.

I had the fuel pump and filter replaced about a year ago. I am hoping this is a simple problem that can be solved by fuel injector cleaner or replacing the fuel filter. I can't hear the fuel pump like I could the last time it went out.

Anyone?

Thanks,

Justin

How many miles on tune up end?
Go a full fuel pressure test and check fuel pressure on cold starting real close.
Post back fuel pressure readings.
Any check engine lights on.
No start unless you hit gas points to a sensor of computer ptoblem.
Needs a full scan with a good engine capable scanner.
Check all sensor readings real good.
MT