I have an old Kenmore 80 Washer and 9 times out of 10 it gets stuck in the wash cycle.
It will go on for hours if we don't stop it and turn it knob manually.

Regular, permanent press and delicate settings all have the same problem.

Is the Timer the only thing that can cause this problem?
Any way I can diagnose or even fix the problem before replacing the timer?

Most likely the problem is within the timer motor (which advances the pointer around), or that the motor isn't getting any power. In either case, timer replacement is the answer.

Thank you!!
I'll replace it and tell you what happened.
Hopefully I can start getting some sleep at night... am I the only one whose wife waits till you are almost asleep to start telling you everything that is broken?! Hehe