300 tdi just stopped?

Hi All,
At my wit's end, pretty much ruined my break, Heres the story recently just bought a 1990 defender converted to a 300
all good have covered about 500 miles in it so far, but on a couple of mornings last week lost a bit of power but just first thing until she warmed up then ran all day really well
Then Xmas eve started playing up and just stopped, did restart but with next to no power not even enough to pull away,first thing I checked was the the lift pump and that was slack could not hand prime it, rotated the engine and still the same so I have fitted a new one and still the same
To cut a long story the lift pump will not pull any fuel from the tank either by turning over or hand priming I have gone back to the tank and the line seems clear,if I cant get and fuel down to the pump I can't really get any further with getting it started can I ? Any Ideas most gratefully excepted

Is the filter full of diesel and clean
Have you pulled the pick up pipe from tank to ensure no crap in there and gauze not blocked
Can you check pump off engine and feel for sucking and blowing on the two ports , when I had problems on my 200tdi I fitted 8mm clear plastic pipe from filter in IP to ensure no air
Similar issue here
https://www.landyzone.co.uk/land-ro...-another-hard-push.366508/page-2#post-5046369

Thanks for your reply
I have tested both lift pumps off the truck and both have strong suction
been back to the tank no gause just a straight pipe and blows through to the lift pump clear
I have had the filter off so still empty looks very clean in there,as far as I understand the pump needs
to suck the fuel to its self before filling the filter so if not sucking it will ever fill the filter...

The pump does have to suck to get fuel from tank. You say that with both pumps you can feel them suck. Take the one off the truck and connect to fuel line and work it with either lever and you should get fuel. If not and line is clear there is a leek in the line allowing air in some where. Like steve3386w above I have a clear section to check for this. A not uncommon cause in an older landy is a pin hole in the pick up pipe.
TIP it is possible to replace the lift pump on the engine with the lever the wrong side of the cam and it does not work.

Without wanting to teach you to suck eggs Have you got the two pipes on lift pump right way round, once both disconnected I got mixed up on mine and needed to double check

Evening Guys, I Today fitted clear tubes flow and return once I got it primed up was turning over nicely with no air bubbles
so was pleased with that, but no way would it even fire, now this truck clearly came a week ago with a new shiny lift pump and a new filter, my son talked me into fitting another filter and said forget turning it over and over trying to get it primed, just tow the thing
and sure enough, he was right it fired up ad has run all day perfectly.
so my lesson for today is no matter how clean a diesel filter looks inside doesn't mean it will run, no idea must be some kind of film over the element preventing the fuel to flow, I wonder if it has ever been run on chip fat?
Had a lovely afternoon pottering around the country lanes in it.
Its a 1990 90 fresh galv rebuild in absolutely mint condition so you can imagine how chuffed I was to get it up and running again
Thanks all for the help always very much appreciated Happy New Year!