A FOKKER 100 ON TKOF AND INITIAL CLB AT 3000 FT RETURN LAND DUE TO A FUEL IMBAL NEAR MAX LIMITS CAUSED BY A R TANK BOOST PUMP PREVIOUSLY DEFERRED AS INOP AND INTERMITTENT OP OF THE REMAINING TANK PUMP. ALL FUEL WAS BURNED FROM THE L TANK.

Narrative

MAINT PLACARDED THE R1 FUEL PUMP INOP BECAUSE THE SWITCH WAS BAD AND THERE WAS NOT ENOUGH TIME TO FIX IT. PER THE PROC IN THE MEL; THE XFEED WAS TO STAY OPEN FOR TKOF INITIAL CLB. SHORTLY AFTER TKOF; I OBSERVED THE FUEL PANEL TO FIND WE HAD A 700 LB IMBAL. SHORTLY THEREAFTER; WE RECEIVED A FUEL ASYMMETRY ALERT WHICH OCCURS AT 770 LBS. AT 3000 FT I ATTEMPTED TO CLOSE THE XFEED SWITCH AND THE REMAINING R2 PUMP SHOWED A FAULT LEAVING US ONLY SUCTION FEED TO THE R ENG. I OPENED THE XFEED AND NOTICED THE R2 FAULTED PUMP CAME BACK ON LINE. THE ASYMMETRY WAS NOW AT 1400 LBS AND CLBING AND WE TRIED TO CLOSE THE XFEED AGAIN ONLY TO SEE THE FAULT RECURRED ON THE R2 PUMP. THE ASYMMETRY WAS AT 1600 LBS AND CLBING AND THE LIMITATION BEING 2200 LBS; I DECLARED AN EMER AND RETURNED TO DFW. THE ASYMMETRY UPON LNDG WAS 1900 LBS AND THE LNDG WT WAS 82000 LBS. MAINT; AFTER GATE ARR; DISCOVERED THAT THE REMAINING R2 PUMP WHICH WAS NOT PLACARDED WAS IN FACT INOP ALSO. WE COULD NOT HAVE FIGURED THIS OUT UNTIL AFTER TKOF BECAUSE THE XFEED FUEL WAS SATISFYING OUR FUEL DEMANDS FROM THE CORRESPONDING TANK.