switch in trunk

Hey i have a 86Grand marquis. In the truck there is a switch and can't figure out whats its for. The switch is a little black box with a button on the top, placed right by the trunk hinge on the left hand side. I've tried pushing the button on it, but nothing happens. the wires leaving from it go under the back seat, and i havent searched further than that. If anybody knows what this button is for, please let me know.

It is the Fuel Inertia Switch. It's purpose is to shut off the fuel supply, from the Fuel Pump, in case of an accident. If you ever have a "no-start" situation make sure this switch ("Button") is not "tripped". Just press it back in. MB