What was found
ON FLIGHT 4855 - CREW REPORTED AT APPROXIMATELY 15 MINUTES AFTER DEPARTURE FROM LGA GOT "ENGINE 1 HYDRAULIC 1 PUMP FAIL" MSG ON EICAS. RAN APPROPRIATE PROCEDURES. ELECTRICAL HYDRAULIC PUMP CAME ON AND OPERATED NORMALLY. APPROXIMATELY 5 MINUTES LATER "ENGINE 1 HYDRAULIC PUMP FAIL" MESSAGE WENT AWAY AND ELECTRICAL HYDRAULIC 1 PUMP TURNED OFF. ALTHOUGH HYDRAULIC QUANTITY WAS LOW (GREEN RANGE) SYSTEM SEEMED TO OPERATE NORMALLY. SEVERAL MINUTES LATER "ENGINE 1 HYDRAULIC PUMP FAIL" MESSAGE RE-APPEARED AND STAYED ON. AGAIN ELECTRIC HYDRAULIC 1 PUMP TURNED ON, HYDRAULIC 1 QTY REMAINED LOW. AGAIN ELECTRICAL HYDRAULIC 1 PUMP TURNED ON, HYDRAULIC 1 QTY REMAINED LOW. CREW DECLARED AN EMERGENCY. EMERGENCY VEHICLES WERE STANDING BY, AIRCRAFT LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REMOVED AND REPLACED THE ENGINE DRIVEN PUMP PRESSURE SWITCH, SYSTEM 1 HYDRAULIC ACCUMULATOR. OPERATIONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.