Engine Wont Start After Initial

[Jack22]

HI, new to the forum

ive recently done an engine swap on my 54plate 2.0tdci mondeo after it blowing up, i replaced it with a 2.0tdci 2006 mondeo engine.

Problems in having are, if i start it up in the morning when cold it will struggle but will start up, with a few clouds of grey smoke. I can then drive it around for up to an hour and a half with no problems at all, very good engine and very responsive but soon as i stop it it wont start again but when ticking over sometimes hunts abit revs fluctuates between 500-1500rpm. We've had it plugged into scanners and code readers and no fault codes coming up, live data shows fuel pressure is around 4200psi. I've put mu turbo and manifold on as mine was a vacuum and the new engine had an electronic type on, I've also put my egr valve on which was clean free and working vacuum type too. I've also tried two different cam sensors and two different fuel rail pressure sensors, also have the original fly wheel sensor off my old engine. There's no leaks in pipes, put new fuel filter on and removed air flow meter tried starting with it out and no success. All the times we have been turning it over it hasn't brought up any fault codes.

Any help on cracking this problem would be much appreciated

Many thanks, Jack