intermittent airlock starting issue 1.4tdci fiesta HELP!

[ahmyfingers]

Hi everyone! first post on this forum.

So i have a mk6 2008 1.4 tdci ford fiesta van. 4 months ago i had 2 injectors and the fuel filter replaced by 'gap diesel specialists'. Since then i have had an issue starting the van 6 out of 10 times. To start it up i have to squeeze the priming bulb a few hundred times to get the engine to fire up. if not the starter motor just cranks.

i have returned to the garage that replaced the injectors, but they say its nothing they have done(they have plugged it in and the injectors are 'fine'). Since then I've had the priming bulb fuel pipe unit and fuel filter replaced at my local garage. this seemed to have solved the issue but two weeks later, the problem returned. Once again the van is refusing to start.

so i have now had the injector leak off pipes and all the glow plugs replaced, yet the problem persists.

once started, the engine runs fine(though the idle speed is a bit 'jumpy' for the first 10 seconds when started from cold), the temperatures are fine, the battery is fine. there are no warning lights on the dash and there are no diesel fuel leaks(the drain plug in the bottom of the fuel filter is tight so i don't think the air is getting in here either). irrelevant but i have also changed the oil, oil filter and air filter.

when the engine is switched off and you pump the priming bulb, you can see air in the clear fuel pipes.

I'm running out of ideas and was wondering if anyone had any advice to help me solve this intermittent problem. Before the injectors were replaced this was a reliable little van.

any help would be appreciated

[ahmyfingers]

so i have had the vans fuel system pressure tested and there are no leaks. i am starting to think there might be some debris in the fuel tank.

has anyone got any ideas??