G4 Quick Silver not booting

Hello all! I have a Power Mac G4 Quick Sliver that refuses to boot. When the power button is pressed it'll light up and the fans will spin up for about 3 seconds then shut off. The Light will only stay on as long as the button is pressed. I've looked around and I can't seem to find a straight answer. I've tried resetting the PMU and I've replaced the system battery. None of the Ram is bad as to my knowledge so I'm a bit confused. Any help would be greatly accepted! Thanks!