Usually it's the result of a loose connection. Have the pump/motor or circuit board been replaced recently?
If it's the wire for your pump then there could be an issue with the motor, but it would be more likely to blow a fuse or trip a breaker before arcing at the board.
Try cleaning off the board with some acetone to see if there's any real damage. Hopefully the it's limited to some charring on the terminal. Be sure to check the back side of the board as well. If the problem goes straight through the board (if a relay burned out, for instance) it will be easier to see from behind.