battery wont stay charged an car dies out when driving on 1991 Buick Regal

I have replaced the battery but if i dont drive it for a few days it goes dead again. And when i drive it down the road the car dies out an i lose all power. But after i pull over it starts back....

Asked by for the 1991 Buick Regal
Have the starting and charging system checked, sounds like you have a failing alternator. Needs alt to work so injectors work correctly.