Right, i have just spent all day futtering around doing various mods,
1. i sat a container of fuel beside the lhm tank and ran a supply and return directly from the pump and the old girl sat at idle sweet as a nut
2. i then ran a line via the fuel filter and again she sat at idle but i noticed air bubbles coming from the return line
3. i then ran a length of brand new hose from the tank to the pump with the return into the container and air bubbles still there and after 30 secs engine stalled
So where next?
fuel leak
*long shot* pick up pipe fractured/leaking inside the tank???? Has this ever happened? ... You appear to have eliminated everything else. After my crap weekend with BX fuel systems that's the sort of trick I'd expect ... 
Doz
2007 Citroen C1 (it's not a real Citroen)(With a complete set of wheel trims)
2006 C4 1.6VTR+ (Alloys no wheel trims)
1982 Mini HL (No wheel trims, no wheels)
1993 Kawasaki GPZ500
2007 Citroen C1 (it's not a real Citroen)(With a complete set of wheel trims)
2006 C4 1.6VTR+ (Alloys no wheel trims)
1982 Mini HL (No wheel trims, no wheels)
1993 Kawasaki GPZ500
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DavidRutherford
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Given what you've done, either the fuel pick-up pipe is fractured and letting in air, or it's blocked in some way that means at idle the transfer pump cannot draw fuel. I can't remember with a BX tank... is the pick-up pipe removeable? I know in some PSA cars they are, but not sure with the BX.
Only other possible alternative is that there's an air leak in the pump itself, meaning that when it only has to draw fuel up 2' of pipe, it doesn't allow any air in. When it has to do more work, like drawing it through the filter, it lets some air in. When it has to draw all the way from the tank, it lets lots of air in, and the engine stalls.
Have you checked the copper washers on the inlet banjo? Alternatively the only way to find the leak may be to use a petrol fuel injection pump to pressurise the whole injection pump an see if diesel leaks out from anywhere.
[spock] Curious, Captain. [/spock]
Only other possible alternative is that there's an air leak in the pump itself, meaning that when it only has to draw fuel up 2' of pipe, it doesn't allow any air in. When it has to do more work, like drawing it through the filter, it lets some air in. When it has to draw all the way from the tank, it lets lots of air in, and the engine stalls.
Have you checked the copper washers on the inlet banjo? Alternatively the only way to find the leak may be to use a petrol fuel injection pump to pressurise the whole injection pump an see if diesel leaks out from anywhere.
[spock] Curious, Captain. [/spock]
this might be a signature
OK so you have proven you dont have a pump problem, as you have had fuel running directly from and to a jury rig set up, and the engine runs fine.
To make life easier you need to have a length of clear pipe just before the injector pump inlet, so that when you do chance across the leak you can pinpoint it instantly.
A prudent step to take will be to replace all the copper washers, or better still change them for Dowty bonded washers.
Air in the return line indicates you have an air leak somewhere on the supply side, do you still have the original steel fuel pipes as these are well known for rusting through, but are easily replaced with semi rigid nylon tube (6mm return, 8mm supply). Idealy you need a hairdryer to form up the bends on the tank end, idealy use stainless steel jubilee clips as they are exposed to the elements under the car.
I have never encountered a fuel tank pickup fractured causing a leak, however its an easy job to pull it out for inspection, and you can clean the fine pickup gauze at the same time.
To make life easier you need to have a length of clear pipe just before the injector pump inlet, so that when you do chance across the leak you can pinpoint it instantly.
A prudent step to take will be to replace all the copper washers, or better still change them for Dowty bonded washers.
Air in the return line indicates you have an air leak somewhere on the supply side, do you still have the original steel fuel pipes as these are well known for rusting through, but are easily replaced with semi rigid nylon tube (6mm return, 8mm supply). Idealy you need a hairdryer to form up the bends on the tank end, idealy use stainless steel jubilee clips as they are exposed to the elements under the car.
I have never encountered a fuel tank pickup fractured causing a leak, however its an easy job to pull it out for inspection, and you can clean the fine pickup gauze at the same time.
Sorry if I'm repeating what has been said elsewhere - its a problem with long threads.
Tank pick-up is under one of the inspection hatches under the back seat and can be removed by unscrewing the plastic ring which may be brittle. I think there are instructions in Haynes.
The priming pumps on top of the filters (with filter by LHM tank) can leak. My comment when I changed the filter on mine was that the whole thing wasn't the best bit of engineering I'd seen - and I could expect leaks round the seal at the top of the bowl. The rubber washer at the bottom of the bowl (seals the bolt) had flattened irredeemably and I replaced it with an 'O' ring which worked (rather surprisingly).
Since you are handy with the plastic pipe - why not get a disposable fuel filter and temporarily by-pass the whole filter/priming bulb setup and see if there is any difference.
Incidentally you will of course have to bleed the pipe from the tank - the thing won't like 10 ft of air when its running.
Tank pick-up is under one of the inspection hatches under the back seat and can be removed by unscrewing the plastic ring which may be brittle. I think there are instructions in Haynes.
The priming pumps on top of the filters (with filter by LHM tank) can leak. My comment when I changed the filter on mine was that the whole thing wasn't the best bit of engineering I'd seen - and I could expect leaks round the seal at the top of the bowl. The rubber washer at the bottom of the bowl (seals the bolt) had flattened irredeemably and I replaced it with an 'O' ring which worked (rather surprisingly).
Since you are handy with the plastic pipe - why not get a disposable fuel filter and temporarily by-pass the whole filter/priming bulb setup and see if there is any difference.
Incidentally you will of course have to bleed the pipe from the tank - the thing won't like 10 ft of air when its running.
just to update everybody , i was sat thinking where to go next and i thought change the fuel filter for the later one over the stat, so took everything of f the spare engine and the took apart the one in the car all looked straight forward so dove in at the deep end.
Had a job getting the later filter housing to sit nice and square and thought well its just a a case of pushing the pipes down a bit , how wrong was i
i was just putting an extra couple of turns on the left hand bolt and the f******* THING SNAPPED and before you say anything i was not hanging of it with a big bar. So plan b i thought we would try and start and see what happened bled water and diesel and yes started but pissing water out and still would not idle, last night i went to revert to old set up and yes you have guessed it .. stripped thread 
so can i tap this out easily or do i dive in deep and swap the head?
by the way i did lift the pick up out of the tank and it is clean as a you know what!
This now leaves us with two duff cars and sharing a £200 r****** to run around in well at least its french!
Had a job getting the later filter housing to sit nice and square and thought well its just a a case of pushing the pipes down a bit , how wrong was i
i was just putting an extra couple of turns on the left hand bolt and the f******* THING SNAPPED and before you say anything i was not hanging of it with a big bar. So plan b i thought we would try and start and see what happened bled water and diesel and yes started but pissing water out and still would not idle, last night i went to revert to old set up and yes you have guessed it .. stripped thread so can i tap this out easily or do i dive in deep and swap the head?by the way i did lift the pick up out of the tank and it is clean as a you know what!
This now leaves us with two duff cars and sharing a £200 r****** to run around in well at least its french!