What was found
(CAN) ON CLIMB (L ENG FUEL FILT) EICAS MSG. RETURNED TO DEPARTURE. FUEL FILTER INSPECTED AND FOUND DIRTY. (NO DEBRIS) TECH NOTED NOT TO THE EXTENT THAT WOULD CAUSE THE EICAS INDICATION. FILTER REINSTALLED. LT ENG DIFFERENTIAL PRESS SW CONX FND CORRODED. CONX CLEANED NR DIFF PRESS SW REPLACED. CKD SERV ON GRND RUN. REPEAT SNAG ON NEXT T/O. FILTER REPLACED AND CKD SERV ON HIGH PWR GROUND RUN. (TC NR 20070201002)