Mounted within the fuel tank, the Mercury Grand Marquis' fuel pump is contained within an assembly that includes the sending unit, much like other cars. You basically need to replace the entire module should you need to replace the pump itself. This will require you to remove the tank temporarily from the car, so you should do this when the tank is nearly empty. The pump is also connected to the main fuel lines and electrical connectors.
Disconnect the negative battery cable.
Remove the cap on the Schrader valve that is on the fuel supply manifold. Connect a fuel pressure gauge to the valve and drain the fuel into a safe container to relieve the pressure.
Raise the vehicle on its rear end using the floor jack, supporting it onto jack stands.
Loosen the metal retainer connecting the fuel filler pipe to the tank if one is equipped, removing its screw with a screwdriver.
Raise your floor jack underneath the tank to support it. It can help to place a board on the jack to protect the tank. Disconnect its straps with a wrench.
Lower the jack and the tank with it until you can reach all the fuel line fittings and electrical connectors on the fuel pump flange. Disconnect all the wires and lines at their quick-connect fittings, then lower the tank the rest of the way.
Clean off all contaminants from the tank surrounding the fuel pump flange using either rags or compressed air; the latter works best.
Remove the six bolts for the fuel pump module with a wrench, or tap the locking ring with a brass punch and hammer to loosen and unscrew it; this will depend on the exact model. Remove the fuel pump unit.
Clean off the tank around the mounting surface and seal ring groove with acetone.
Coat a new seal ring lightly with grease and install the new ring within the tank's sealing groove.
Insert the replacement pump assembly into the tank, making sure you don't damage the filter.
Apply the bolts to the flange, or screw the locking ring in place until it is against the locking tab stops--you may need the punch's help.
Raise the tank back into position on the jack, reconnecting the fuel lines and electrical connectors, and strap it into place with the strap bolts.
