20080301832719I

(-23) Nwa flight #1749 departed kmsp enroute to mmcz. Shortly after level off the first officer noticed a fuel imbalance greater than that allowable. The amount of fuel used (total fuel loaded minus fuel onboard) and the fuel burn numbers were correct, however it appeared all of the fuel, for both engines was being burned out of the right main fuel tank. After discussion with dispatch and mtc, the decision was made to divert to kmem. It was discovered that the fueler in kmsp had left the mode select switch on the refueling control panel in the refuel position and the refueling valve for the left wing in the open position. Also, a relay, removed after the event, was determined to have failed in such a manner that no electrical power was available to close the two open fueling valves when the landing gear selector was raised. The failed relay prevented the flow of power to the shut section of the two valves involved. Thus the fuel boost pump pressure moved the fuel from the center/right wing tank to the left wing tank.