kenmore 80 washing machine wont let out water

To make sure I understand...
1. The washer is full of water.
2. It will agitate if the timer is set to the beginning of a wash cycle.
3. If you set the machine to the final spin and pull the timer knob out, all the machine does is hum.

If all of this is correct, it sounds to me like you may have a timer problem. To be specific, it sounds like the timer is giving the "run" winding power, but not the "start" winding. You could check this theory by pulling the timer knob out, and when the washer is humming, apply sideways pressure to the timer knob in all different directions (without pushing the knob in) to see if the motor will then start with said pressure applied. If it does, that pretty much guarantees a bad timer. If it doesn't run, it still doesn't mean the timer is good, but it does mean the problem could be elsewhere as well. Elsewhere would include wiring connections, either at the timer or at the motor, or possibly a problem with centrifugal switch problems (on the motor). If you still can't figure it out from the first "trick" I gave you, then a volt/ohm meter would be required to continue. Let me know if this is the case. Good luck.