Zetec_mk4_XR3i

Wondered if anyone could shed some light on this one...did a search on here but thought I'd give some more details.

Got an 03 plate Focus 1600 petrol, and the fuel gauge isn't working. Light is on and showing as empty after putting fuel in. The gauge moves very slightly when ignition comes on.

The car had a replacement fuel pump fitted before I got it, and after checking the wiring, it turns out that have fitted it cowboy style by cutting a hole under the rear seat. The wiring had been messed up a bit so peeled it back and put to how it should be. I believe the sender and pump are the same unit? Any ideas?

Cheers