I HAVE AN 1988 GT CONV. ,I HAVE REPLACED THE FUEL PUMP BECAUSE OF VIBRATING SOUND. THE NEW PUMP WAS QUIET FOR ABOUT 4 MONTHES NOW SOUND AND VIBRATION IS BACK. CAR RUNS FINE , IS THIS COMMON ?

 

Was the old fuel pump not providing the proper pressure? You may have just changed it for nothing.
When you turn on the key, but don't start the car you should hear the pump pressurize the system. Then as the car is running you should also hear the pump running, but what type of vibrating sound are you talking about? Most of them make a mid to high pitch sound that sometimes varies with electrical loads of the vehicle. Can you post a sound clip?

 

I CHANGED THE PUMP BECAUSE OF THE NOISE. CAR RAN FINE. THE PUMP SOUND IS NOTICABLE FROM OUTSIDE THE CAR WHEN RUNNING. I DON'T HAVE A SOUND CLIP. THANKS