What was found
SHORTLY AFTER TAKE-OFF THE RIGHT FUEL GAUGE ROLLED BACK RAPIDLY TO 500 LBS LOWER THAN THE LEFT SIDE. THE MASTER CAUTION WARNING LIGHT ASSOCIATED WITH THE RIGHT FUEL GAUGE LIGHT ILLUMINATED. EMERGENCY WAS DECLARED AND DIVERTED TO ALTERNATE AIRPORT WITH LONGER RUNWAY. LANDING WAS UNEVENTFUL. MAINTENANCE SUMPED THE FUEL TANKS, PERFORMED AN AIRCRAFT OVERWEIGHT LANDING INSPECTION AND DEFERRED THE FUEL QUANTITY SYSTEM PER MEL. FURTHER TROUBLESHOOTING AND OPERATIONAL CHECK WAS PERFORMED OF THE FUEL QUANTITY SYSTEM, WITH NO DEFECTS NOTED. AN OPERATIONAL CHECK FLIGHT (OCF) WAS PERFORMED WITH NO DEFECTS NOTED. AIRCRAFT WAS RETURNED TO SERVICE.