The main two parts of a dishwasher that move the water around are the pump and the motor. Both of these parts are located beneath the lower sprayer arm. Although the pump is very important to the functioning of the dishwasher, it can often get clogged by food and detergent. To clean it, you will have to remove the lower sprayer arm and disassemble the pump. Follow these steps.
Disconnect the power from the dishwasher. This may require unplugging the dishwasher or throwing the appropriate switch on the circuit breaker.
Remove the lower dish rack from the dishwasher.
Remove the lower sprayer arm from the dishwasher. This may require unscrewing a bolt on the arm, or it may require pulling it out while gently rocking it from side to side.
Remove the screen beneath the sprayer arm. Unbolt the pump housing and remove it as well.
Unscrew the bolt beneath the pump housing, and disassemble the pump. The pump should be separated into the following pieces: upper impeller, food disposal blade, spacer plate, impeller hood, flat plate, O-ring, lower impeller and washers.
Fill a bucket with water, and add a small amount of dishwashing detergent.
Examine the parts of the pump for damage. Replace all damaged pieces. Soak the other pieces in the dishwashing detergent and rinse with warm water.
Reassemble the pump, reversing Steps 3 through 6.