Never seen that one before. Is it possible that the impeller is not tight to the pump shaft? Maybe the motor is spinning but the impeller isn't, then it catches for a while, then stops again? If you take out six screws on the front of the pump (four short ones on either end, and the two long ones that go through the top and bottom of the motor), you can pull the motor and impeller assembly out. There is a set screw that tightens the impeller to the motor shaft, maybe that wasn't tightened correctly or something. I would pull those six screws, start up the pump, and see what you find...