What would cause the toyota camry evap purge valve noise?

The buzzing noise next to the Toyota Camry gas tank is most definitely the evap purge valve that releases the negative pressure from Your fuel tank. This is a standard process vibration. The purge valve ticking noise is most definitely natural and should not be heard inside the cab while the windows are closed. If it's too noisy inside the car, replace the valve. When You're refueling, the purge valve can leak vapor through it and into the engine. This will allow the car to bring the gases into the engine when it's not meant to get them, and it will cause a hard start and run rough until the excess fumes are burnt. The cost of the replacement valve will range from $15 to $45, based on the size of the valve and if it's an aftermarket or OEM product.