No fire, won't start

My car has been running kinda bad lately and all of a sudden it shut off on me. Now it turns over, but doesn't produce spark. The shift light does come on when I try and start it now so it has to be the crank sensor right? Well I replaced the dis and I got my mechanic to test the crank sensor and he said its all working fine. Would could it be? Also I fiddled with the fuel shut off switch a bit. Could it be that that is still on? How do you know when the fuel shut off switch is activated? Thanks.

It's the crank sensor....also check the balancer to see if it is broken (check to see if the bolt is broken that secures it to the crankshaft). If the car has been sluggish lately, and yopu have been hearing a low pitched rumbling like some sort of exhaust leak, that is the sign of a balancer going bad......and find a new mechanic........

Yeah I'm getting the crank sensor replaced right now. About the balancer ever since i got it (june 2002) I've noticed that it was a bit louder (sorta sounds like a truck) i thought it was just an exhaust leek coming from near the manifolds on the drivers side. Is this the balancer? What exactly is the balancer and where is it? How would this be replaced? Buying a hole new balancer or what? Thanks a lot.