Dishwasher Not cleaning well

Dishwasher Repair
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1

My Whirlpool dishwasher does not always clean well. I suspect the spray arms are not rotating. When I quickly open the door, while running, I see no evidence of the arms moving. I can hear the water gushing inside but don’t think the spray arms are moving. I did replace the lower rack on this unit a while back. How much of a gap should there be between the lower rack and the lower spray arm? I see a gap of about 3/4" between the rubber bellows and the tube that directs the water to the upper spray arm.
I suspect its not sealing well enough to create the required pressure to spin the arms. I was going yo try to bypss the switch on the door in order to see more closely to what is happening but that may get messy in the kitchen.

Any Ideas on the gap for the bellows?

Dishwasher has been in use since 1992. On average it gets used twice a week if that.
Maybe it’s time for a new one? LOL!

3

Been diagnosing the dishwasher. The only thing I find that is questionable is the drain valve stopper. I did the test procedure, per the service manual, and found that it does not hold a vaacum. I push the stopper all the way to it’s seat, then put my finger over the vent hole, and the stopper comes off it’s seat about a 1/4". Nothing looks damaged or worn but obviously the diapragm in not holding the stopper completely closed.

Would this cause enough pressure loss to prevent the spray arms from spinning?

My guess is yes.

Everything else checks out. No blockage and plenty of water pressure to the unit.

Rich.