Rear buzzing or humming sound

I have a 91 Metro that is making a loud, constant buzzing sound at the rear of the car. I assume it is electrical in nature because it changes pitch when the lights or wipers are turned on or off. I am assuming it has someting to do with the fuel pump. The car runs fine. Can anyone offer any suggestions?

Thanks

I also have a 91 but haven't heard the sound you are hearing. It sounds as though you have already figured it out as being the fuel pump. I would try placing the key to the ON position without actually starting it and see if you hear the noise. On some vehicles the pump begins working at that point, but I'm not sure if this is the case with our 91s.