Keep getting air into my 2.5 TD fuel feed, and can't isolate the air leak, thinking of replacing all the tubing with new with Fuel line and brass fittings. How about the filter, can you just replace with a 200tdi filter ? , they seem simpler and not so many connections to for air leaks . ? What size are the fittings, looks like 8mm Od piping with a 6mm internal dia.?
No - the Lucas pump needs to have the lucas head, or a head which preforms the same way. The Bosch heads don't have a air purge system.
As you have found air will stop your Lucas run engine dead, not so a Bosch injection pump as it self bleeds, so basically the Bosch head just simply has an in and an out, diesel air the lot. If you fitted this to your pump you would have no end of trouble.
I had this problem with a 2.5NA (for all intents and purposes the same set up). It ended up being a full fuel system pipe work refit after diagnostics. I am actually currently working on another diesel car which has an air issue just now and I am doing exactly the same for it as I did the 2.5NA years ago. Thing is a pig to start in the morning but then runs fine all day, did the leak off pipes checked for leaks, checked filter heads and all sorts and set up an experiment 2 nights ago. I took a clean 5 litre can, filled with with diesel from the return line of the vehicle with the engine running (to get good clean filtered fuel).
I extended the return line away from the rubber hose as it leaves fuel pump on engine with a piece of clear pipe and put it into the can. I then extended the rubber feed into the pump with another piece of clear pipe, so I now have NO filter (take care) and 2 pieces of clear pipe going into a can with clean diesel. I started the engine and let it run, I saw air bubbles flying down the clear pipe then the engine sat nicely with no air. Switched it off and left it over night, following morning, some 15 hours later, vroom thing starts instantly, better than it has in years. Leave it another 24hrs, again vroom it starts up. So I have now confirmed where the air leak is NOT.
I then added the filer back into the equation but connected the input side into my clear pipe back to my can - so now the filter is the only addition, left it again for a day and again twice after 12 hrs or more it starts perfectly. I now know that the filter and engine bay fuel piping is OK.
Plan now is to replace all the piping back to the tank. It might only be the feed or might only be the return, but this thing has steel pipes and to be honest it's just asking to fail again if I leave it... so have a think about this experiment, set it up carefully and in a way you can drive the car using your new make shift tank for testing.
See how that goes.
Also, another simple thing would be to get a bit of air hose into the system AFTER the filter head to see if it's sending air filled fuel to the pump. Also, have you checked your air bleed off on top of your filter pump? 100% absolutely are you sure, air can pass through the banjo via the tiny hole?
Check the injection pump unions, bleed screw etc. too. Leave nothing t chance.