Get a repair manual and look at the wiring diagram for your fuel pump system. Get your codes to understand which side of relay is grounding out.

Pull your connectors and run resistance tests on each strech of wiring harness as per your wiring schematic. Wiggle the section of wiring harness you're checking as you go.

Pinpointing a ground isn't easy though. Look for darkened insulation. Where insulation is exposed to heat, double-check it. If it's discolored and stiff, it will crack. Easiest way to check is take a dirty thumb and rub along the wire, the dirt will catch in the crack and make it more obvious.

Also double-check around where the wiring harness hits sharp edges. Vibration breaks occur a lot, so this is your first stop when approaching pinpointing a short to ground.