A DC10 FLC DECLARED AN EMER AND DIVERTED AFTER THEY DISCOVERED UNCOMMANDED FUEL DUMPING THROUGH THE L WING DUMP NOZZLE. FLT ATTENDANTS WERE NOTIFIED AND NORMAL FUEL DUMPING PROC WERE FOLLOWED TO COMPLY WITH MAX LNDG WT.

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ACFT STARTED DUMPING FUEL ON ITS OWN. HAD TO DETERMINE THE SOURCE OF DEPLETION OF FUEL IN TANK #1. SO DEPARTED COCKPIT WITH FLASHLIGHT AND DETERMINED DEFINITELY THAT FUEL WAS DEPARTING THROUGH THE L WING DUMP NOZZLE. NORMAL FUEL DUMPING WAS STARTED DOWN TO ACFT MAX LNDG WT. UPON TERMINATION OF DUMPING FUEL; NOW THE L WING NOZZLE CLOSED PROPERLY. LANDED WITHOUT REVERSING ENG #1 BECAUSE WE WERE NOT SURE IF WE COULD HAVE HAD ANOTHER LEAK IN THE L ENG AREA. FIRE DEPT DETERMINED THERE WERE NO OTHER LEAKS ON L SIDE OF ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: DURING CLBOUT ON A FLT TO LONDON; THE RPTR (CAPT) NOTICED THAT THE BLUE FILL LIGHT ON THE FE'S PANEL WAS CONTINUOUSLY ILLUMINATED (CONTINUOUS FUEL TRANSFER); BUT ALL ENGS WERE USING EQUAL FUEL. RPTR STATES THAT NO AIRLINE HAS A COCKPIT PROC FOR THIS SIT. THE CAPT SENT THE SO TO THE BACK OF THE ACFT WITH A FLASHLIGHT AND THE SO DISCOVERED THAT A MASS OF FUEL WAS BEING DUMPED FROM THE L WING DUMP NOZZLE WHEN HE PEERED THROUGH THE CABIN WINDOWS. THE FLT ATTENDANTS WERE TOLD TO CANCEL SVC AND STANDBY FOR FURTHER INFO. AN EMER WAS DECLARED; AND FUEL WAS DUMPED TO MEET MAX LNDG WT. THE FLT WAS DIVERTED.