Should I be able to hear the fuel pump running with the key on, but the engine not turning over?
The pump was replaced on a near annual basis with several shops, which is why I don’t trust Gm pumps. Just banged under the center. But gee yours is accessed under the back seat so easy.
When you turn the key to on, the pump starts and runs for a few seconds to build pressure. Turn the key off again and have to wait a few seconds before you can repeat the sequence. When the car starts, the pump is then again commanded to run.
I’ve used a 2x4 too, but don’t hit the tank so hard to dent it. Pretty hard to do though o your knees reaching under the tank with a hammer.