GE triton dishwasher won't drain. Model number gsd5130d02ww. Has been working fine and would sometimes have the usual small amount of water in the bottom. Now has considerable amount of dirty water. Dishes are dirty.

I have checked the drain line(no air gap on this one). Checks good. I have replaced the piston assembly and the check valve on the collection chamber. Both looked good but changed anyway. Screens are all clean. Using the service sheet at the bottom of the machine and I put it into the test cycle to see if the drain pump would come on. It does, but no water flows from this pump. You can feel the pump running in your hand but no water is moving. I am not sure what this means but the dishwasher is still not draining. What to do?

John