Fuel problems

Hi All. New to the forum, so apologies if this item has been covered before ( no doubt it has!). I bought a 52 plate TD4 Man for peanuts off a friend. He had just spent a fortune replacing the clutch, and then the fuel pump went. Anyway, its on my drive now ready for the new (working second hand unit) to be fitted. I've bought the high pressure pump, and also the in tank pump. I'm assuming it's the in tank pump. I haven't bothered doing anything with the HP pump yet, until I eliminate if it's the in tank pump.
I've removed the in tank pump, and have tried refitting, but seem to be struggling with the locking ring.Are there any tips for refitting this (other than take it to Land Rover!).
The car is a 5 door GS
Thanks in advance for any assistance !

Recently removed my in-tank unit and was struggling to refit locking ring.
Cured by removing seal from unit and fitting it carefully into top of tank, half of the seal is now inside the tank....
Carefully slide pump/sender unit into tank, being careful not to dislodge the seal, and the locking ring now fitted easily!
There is an orientation to the pump/sender unit, with a "lump" on the sender rim that locates into a recess on the tank!

Good luck,

Chris

Thanks for this Chris. I'll give it a go tomorrow and report back. I'll take some photos and post up. Cheers!!