I have a newer craftsman pressure washer, that has sheared two keys now. The pump turns free by when off the motor, the motor runs good, and they seem to go together nicely. It is still easy enough to start, so I assume that means nothing in the pump is bound up. I have never ran this without water ran through it. Works like normal when the key is replaced, but then continues to chew the key after a while. What is causing this? I fear chewing up too many keys is gonna tear up my crank or the pump input. Don't want that!!! Any idears greatly appreciated.