If your sump pump smells bad, there are a few things you can do to try to fix the problem. First, check to see if anything is caught in the impeller or in the intake screen. If there is something blocking the flow of water, it can cause the pump to overheat and smell bad. You may also want to check the discharge pipe to see if anything is blocking it. If the discharge pipe is blocked, water can back up into the sump pit and cause an unpleasant smell. Finally, you can add a deodorant tablet or liquid to the sump pit to help control any odors coming from the pump.