Where is the access door for fuel pump on a 94 z28?

On a 1994 Camaro Z28, the fuel pump access is located in the trunk, not under the car. You'll need to remove the trunk carpet and usually find a circular access panel. The exact location of the panel within the trunk varies slightly but it's generally near the back of the trunk, often to the left or right of the center (passenger side being more common). Sometimes there's a small panel directly over the pump, sometimes a larger section of the carpet may need to be lifted or removed.