Is there a picture of this? I am not sure, but I can absolutely hear no mechanical noise, or whirring coming from the CD drive. My PS1, SEGA Dreamcast, Saturn, they all make noticeable read-access noises.
I was just thinking also...does the CD access light work in ANY way at all? (That may give some direction help to diagnose the problem)
*EDIT* I just found this quote of yours... "The system boots up, but just like before, the CD does not spin at all. The CD access light does not lit up."
So...without knowing exactly how everything should work...I would say it's possible the drive isn't actually getting any signals to "do anything"...and that's why it isn't "doing anything".
This....

( apologies for the upside down photo

)
Goes into this...

And then through the interruptor module within the casing...