What was found
AIRCRAFT RETURNED DUE TO FUEL LEAK IN THE CENTRAL MAIN TANK AND "USING RESERVE FUEL" AND "INSUFFICIENT FUEL" MESSAGES DURING CLIMB; SO FLIGHT CREW ACCOMPLISHED THE QRH 12.7 PROCEDURE. AIRCRAFT LANDED. PERFORMED A FQIS OPS TEST IAW AMM 28-41-00 TASK 710-801, A FQIS WITH THE FUEL MEASURING STICKS COMPARISON CHECK IAW AMM 28-41-00 TASK 720-801 AND A FQIS TEST IAW AMM 28-41-00 TASK 730-801, NO FAILURES AND FUEL LEAKS WERE FOUND. FUEL QUANTITY INDICATING SYSTEM TEST WAS PERFORMED IAW AMM 28-41-00 TASK 730-801, TESTED CORRECT.