How many wires go to the sender unit
cos if its only 2-3 its not a purge pump its just a sender unit & you will be wasting ya cash replacing it

if theres 4 or more its worth a try
but im pretty sure mondeo tdci dont have electric pump in tank

try booting the tank from underneath as if its got a in-tank pump
& the motor is jammed this may free it off
we used to do this on pug hdi's as they are prone for in tanks going

id get a inline hand pump
commonly known as a bollock lol
connect it to the fuel supply pipe that goes before the fuel filter
Disconnect the suply pipe to the main fuel pump
then pump the bollock till fuel comes out the pipe at the pump
make sure all the air is out n its just diesel coming out
re connect the pipe to fuel pump but leave the hand pump connected
get a decent battery & crank the car over aswell as pumping
the hand pump
if its air locked this should get you running but sometimes
it doez take a while for all the air to come out the system

the common rail systems are a propper arse to bleed up

if it was a normal tddi you could do the same routine to bleed it up but leave the injector pipes loose till fuel shoots out them then nip them up n it would run

tdci are a bit different & ya not supposed to leave the injector nuts loose
altho if we had 1 at garage that was a tit to bleed we would do
Just dont stand anywhere near it as its a lot higher pressure on a tdci than a tddi


hope this helps you
or even someone else

if you was local to me i would of come n had a look