AndyTheBubble

Hello All.
I would appreciate some help.
I few weeks ago - I replaced injector number 5 copper seal because it was blowing gases and partial combustion tar. Before this - the vehicle started every time, even it is was a longer crank than originally known.
To remove the injector, I used a special toolset - all went well, however I was mindful that I was removing many small pieces of the injector solenoid mechanism.
Once the injector job was complete, the engine started eventually and ran smoother than ever. However, it would not re-start when the engine had been previously started, not just a warm coolant.
Therefore I am adamant that it is not building up enough fuel pressure to start sufficiently because it is pulling in air at some point.
So only when it is left alone (overnight - on charge, - will it start)
I have replaced o-rings on pipes, re-built the injector head, changed the crank sensor, but I have this issue.
Unfortunately my generic tool has not pulled any DTC's
Is it possible the injector is partially damaged, closed during cranking, causing a low pressure as it is spilling into the return line?
Whilst the engine was running, there were bubbles in the lines, but the cleared away....