I recently had to replace the fuel pump (motor only) and the fuel pump relay in a V6 Mustang. I just want to update this forum so that people can find the relay in the future.
First thing to note is that the relay is housed in a Constant Control Relay Module (CCRM). This module contains the relay for the Fuel Pump, Cooling Fan, and Air Conditioning Clutch.
In our 1998 Mustang V6, the location of the CCRM is behind the passenger side wheel well plastic cover. Looking at the wheel dead on - it's found at around the 1 o'clock position. To confirm it's location without removing any plastic wheel well cover - pop the hood, and look for a wire harness routing from the engine compartment INTO the passenger side front fender (near the air cleaner). Flash a light in there, and you'll see a connector attached to the module.
I'll save you some headaches in finding the right size tool to remove the connector as well - I used a 5mm nut wrench to remove the connector from the module. Do this first so that you can access one of the two bolts that holds the module bracket to the fender.