2002 Century Not Starting
 

Hi, I'm kind of new to GM products and am having an issue with my mother's 2002 Buick Century (3.1L) I'm hoping someone can help with.
Roughly a month ago, the car would have problems starting. It would crank over and eventually fire and run. Now however, it will not even fire.
I've checked for spark on all cylinders and there is good spark. The fuel pressure at "key on" is 48 psi. I replaced the fuel filter and cut open the old one to see how dirty, and it was clean.
I have not checked the crank or cam position sensor functions yet, but if there is good spark when cranking, I would assume they would be functioning correctly.
I tried using starting fluid and the car will run with that.
Is there an injector control module, or is that part of the ECM?
I've been searching several forums and found the basics that I have already checked, anyone have any ideas? Thanks