1993 Ford Station Wagon 6 cyl Front Wheel Drive Automatic 250000 miles

I have a problem with my fuel line i think. ive took the car to the inspection station and failed. they told me that i have a fuel leak or there is air in my fuel lime. i can not visually see the leak but i know there is one, everytime i fill up the tank the gas goes as fast as if i only put in a half a tank. can anyone tell me how to fix this problem.