My dishwasher has a 1.5" x 2" chrome cap rising above the sink. Water flows upwards inside this cap from the dishwasher and should return to the dishwasher. I took it apart and cleaned it out. The water flushes out of the cap onto the floor. How can this be corrected.

Unless I miss my guess that cap is actually a vent to your drain. It should allow air in and out of the pipes to allow proper draining without siphoning or gurgling. My guess is that your drain lines are partially plugged or even under sized. When water leaves the washer it is under pressure from the drain pump. Lets say its puming 4 gallons a minute but your drain can only handle 3 gallon. That cause it to back up into you chrome vent. Rod out your drains and maybe remove and clean the P trap.