1990 Acura Integra gas leak

i noticed a gas leak dripping from near the rear drivers side tire. it only leaks when the car is on. its not pouring gas but it does drip fast. my auto shop teacher said if i rubbed a bar of soap over the gas leak it will fix. i tried that but it didnt help. it is not leaking from a line its just leaking out of a metel crack. i think it is the gas tank but me teacher said all it needs is a new fuel pump. does that sound right? thanks for your time.