my grand prix wont start do you know why?

You may not have primed the fuel pump... When you run out of gas, you need to turn the car to the 'on' position just so all the accessories turn on and light up. You should hear a very quiet hum or whine from the back of the car for a few seconds. That is the fuel pump pumping fuel to the engine... Now turn it to off and repeat three or four more times. Then try to start the engine.

change the fuel filter too. it can have lots of debris from the low amount.

You need to prime the fuel pump. You may have damaged it by driving til you ran out of gas. The fuel pump uses the fuel to cool itself, so if you run completely out of gas, you can burn up the motor.

probably need fuel filter.....