Gateway 505gr Not powering up

I am working on a Gateway 505gr and the LED power light next to the 24 pin mobo connecter is on, but the machine will not boot up ( no fans, no hard drives, not even the fan in the PSU). I have jump the PSU using a piece of wire connected to the #16 green pin and a ground and the PSU fan would start (at this point i tested all pins to make sure they were producing the correct voltage using a multimeter and they were). Could this be a bad power switch or a bad motherboard?