What was found
DURING CRUISE FL350, RECEIVED A MASTER CAUTION LEVEL 1 ALERT FOR HYD PUMPS. ALL 3 LEFT EDPS WERE IN THE OFF POSITION (NO PRESSURE AUTO MODE ). SELECTED HYD CONTROL SYS FROM AUTO MODE TO MANUALLY MODE AND ALL 3 LT PUMPS TURNED ON AND PRODUCED PRESSURE. SHUT ENGINES DOWN. ENGINE RUN WAS ACCOMPLISHED AGAIN. LOOKING FOR PRESSURE DECREASE AND INCREASE WITH 2-3 REVERSABLE MOTOR PUMP OFF. ALL LEFT PUMPS SELECTED OFF, AND RIGHT REMAINED ON, PRESSURE DROPPED AGAIN. 3 LEFT PUMPS SELECTED ON AND PRESSURE INCREASED. REMOVED AND REPLACED THE HSC PER MM 29-08-01. RAN ENG PER JRH. ENG DRIVEN PUMPS OPERATE NML LEFT ON, AND RT PUMPS IN ARMED POSITON. OPS NORMAL.