Air in fuel need help!

Hello, i have used this forum quite a bit for problem solving but never need'd to post untill now.

I have a 2005 ford fiesta 1.4 tdci that is a right bugger to start first time and seems to be letting the fuel go back into the tank and getting air in the fuel system. When it is running i have no problem untill i turn the engine off, so far i have changed

fuel filter

leak of pipes (2leak of pipe clips)

the manual hand pump with associated pipes

checked underneath for leaks and noticed there was a minute leak were the fuel lines run up towards the tank which had rubbed on the body, i put some glue around it with a pipe and jubalee clips to see if this was the problem then get a replacement but it hasn't done anything.

put a one way valve in the feed fuel pipe

I had the injectors done about a year ago for leaking but as far as i can see there is no diesel leaking around them and im not getting the same symptoms i was getting such as no power and diesel fumes in cabin.

ive put the injector pump feed fuel pipe in a bucket of diesel to see if it was that but it started first time and ran lovely so i dont think it is that.

I am at my wits end now i cannot see were the air is getting in. Last thing i can think of is changing the fuel lines.

Any help would be appreciated please.

cheers

jake.