Daz is completely correct, this information is addition to his excellent information.
If you are desperate to get the thing running again until you can get a pump ordered, and there doesn't seem to be anything wrong with the motor, it can be temporarily repaired. If the motor kind of flips when you turn the impeller, then the motor is fine. Unfortunately it means that the impeller shaft has disengaged from the inner motor sleeve.
Take a flathead and work it under the impeller.
Gently lever the impeller out of the motor housing
The shaft of the impeller is very small, about the size of coathanger wire.
After removing the impeller, you will notice three flat spots on the shaft (this is for 8181864, newer models may be different). These flat spots are where the plastic went to bond the impeller shaft to the inner motor housing.
These areas need to be filled with some sort of epoxy. I used 50 minute marine epoxy. It worked ok, but it the leftover did not set as hard as I would have liked.
Coat the shaft near the impeller with a little vaseline
paint the shaft with epoxy (a small watercolor brush works well, but you can use a toothpick), and try to fill the three flat spots with epoxy. Don't over do it. a thin coat is all you need.
Shove the shaft back into the motor housing. Watch the area where the shaft enters the housing, you may need to wipe off any excess epoxy. A little buildup is fine, the vaseline will keep it from sticking to the shaft.
*** I pressed the impeller all the way in, I don't know if that is right, but it still worked.
Let it cure, reinstall it, wash your stuff.
P.A.
December 2008