Series 3 Still not fuelling (diesel)

Hi all, I've posted about this issue before, but it's been a while, so as I still have about the same amount of fuel getting through to my injectors as I'm likely to have both hair left on my head and money in the bank at the end of this project, I thought I'd put another shout for help out.
So, from the start, I refitted my engine, and now I want to start it, but fuel is the issue, I get fuel to the injector pump body bleed screw, and it seems to run clear, so I tighten it and crank it for as long as my battery can stand, and bugger all arrives at the injectors, so I tighten them back up, but then after 30 seconds or so I see air rising back up the fuel feed pipe (clear hose) from the pump towards the filter, so I bleed to the pump again and more air comes out, then I just seem to keep going through this process to no avail. I always seem to have air in the feed pipe. I should add, I've replaced the pipe from the lift pump to the filter, that includes the link back to the injector pump as I managed to split it being a clutz. So the question is, do you think the air is getting in, and if so where, or I'm not getting it all out properly? Thanks in advance. John

Possibly a leak between fuel tank and lift pump. It won't leak much diesel out but will happily suck air in.

If youre stuck rig up a temporary gravity feed from a bottle direct to injection pump, if it runs ok feed further back ie filter, lift pump, pick up pipe.

If it doesn't help the problem is the injection pump.

Possible split diaphragm in lift pump. Worth checking as I believe this can allow diesel into the engine oil and air from the crankcase into the fuel.