Hi there and thanks for looking

Where do I start lol well I have got a problem with the starting of my focus 1.8tdci we recently did the head gasket and had everything decoked (before I did all this I had a cold start issue) put it all back together and it would start right, it will start for 2 seconds then die so we noticed when started that the actuator start s up normal then goes straight to full open causing the car to die I then took the arm off the actuator and the car starts fine but and doesn't cut out now we have check the ecu for codes and there's nothing stored please help someone have eexperienced the same problem any thoughts will greatly be appreciated