What was found
AFT CROSSFEED VALVE IS INTERMITTENT IN OPERATION. THE VALVE FAILED TO OPEN WHEN COMMANDED. AFTER SEVERAL CYCLES OF AFT CROSSFEED VALVE SWITCH, THE AFT VALVE OPENED, EICAS AND STATUS MESSAGES WERE PRESENT, WHEN THE VALVE IS COMMANDED, THE VALVE FAILED TO CLOSED. AFTER SEVERAL CYCLES OF THE AFT CROSSFEED SWITCH, THE VALVE CLOSED. VALVE DISAGREEMENT LIGHT AND DISPLAY OF FUEL SYSTEM SCHEMATIC CONFIRM FAULT. FWD CROSSFEED VALVE OPS NORMAL. R & R THE AFT CROSSFEED VALVE IAW AMM 28-22. ALL CDCCL REQUIREMENTS COMPLIED IAW SFAR 88. OPS CHECKED NORMAL. OK FOR SERVICE.