Try using easy start spray. Spray into air inlet. If it starts her and she then dies out after starting you know its a fuel problem. If runs but wont start again when stopped, its a sensor issue of some sort. IIhad a laguna that did that. Easy start and she started and ran until stopped. Took a while but it was a faulty crank case sensor. Wasn,t kicking in when starting, but worked when engine was running
As you split the fuel line, could there be air in the line? Stopping her building up pressure?
And a question to the forum, how do you bleed a td4?
About to change fuel filter myself, so going to watch this thread.