2002 Hyundai Accent delay in filling fuel in the tank

I am writing to you from Libya.I bought this Hyunda Accent-Hatch back 2002 model from American imported car in Libya last year March.I ve this problem since I bought this car while filling fuel, the fuel doesnt flow in the tank very fast and sometimes eject from the tank, evnethough ther tank is half or quater empty.I saw a black box under the bumper adjacent to the fuel pipe, contains of fine cut about 2mm diameter carbon material filled the box and they comes out through the tube near the fuel pipe which they are attached. None of the mechanics are aware of this carbon materials or the problem. There is no problem in starting the car or the in injection or speed. Petrol Filter is good condition as said by my mechanic. Kindly help to solve this problem.