I took the pump off, but I can't see anything in there. I can turn the wheel by sticking my finger in there, but it feels pretty stiff.
How freely should it turn?
I also pulled the motor off and looked at the coupling, but I can't tell if there is anything wrong with it or not. I didn't take off all three parts, but the two parts I can see don't appear to be broken (they do look a bit worn though; the holes on the middle piece look kind of bored out).
What am I supposed to look for to tell if the coupling is bad or not?