I presume there is just one plug that plugs into the PCB on the back? If so ideally you need to know the respective live(s) to check. Not knowing Escort I woulden't know, do you have a wiring diagram?

More than likely a live problem tbh as both gauges don't work the only reason i said check is because you said the fuel gauge moves indicating this is getting power from somewhere.

You will probably have a blue and a green wire, I can tell you it will not be these so thats 2 eliminated for you!

Martin