Difficult starting after standing several days or even one day

[johnaboy183]

Hi,
I posted on this topic way back when and it has never resolved no matter what I've tried.
Decided to tackle it again so seeking views or advice again.
The car is a 2.0TDI 170 (2010) which I have had from new and still only has 22000 miles on clock.
The car will either start first turn of the key or will turn over for a long period either without a start at all or mostly with a reluctant start. Once running it is fine and will restart straightaway over the next hour or so. It runs faultlessly, no misfires and no fault codes. The battery is excellent and the engine spins over easily.
The problem is that it is so unpredictable as to when this will happen (but more than 50% of the time).
VCDS shows no fault codes and neither does my Launch 123E diagnostic.
I have long suspected fuel drain back or no residual pressure in the fuel lines due to a leak but can find nothing visibly to evidence that.
I ran fuel pressure tests with VCDS and they show:
Coolant Temp : 85.5 deg
High fuel pressure (actual) 288 bar
High fuel pressure (specified) 248 bar
High fuel pressure control status 15.0
High fuel pressure control valve 18.9%
High fuel pressure control deviation -5.10

Most of the above seems ok to me but not an expert so any thoughts very welcome.
In VCDS you are supposed to be able to measure residual fuel line pressure after switching off then back on but not started. Mine shows zero for that reading but that could be that my VCDS is an old variant and cant record it or there is indeed a fuel line line leak or the residual fuel pressure retention valve is faulty.
Any thoughts or different VCDS items to try I would really welcome and be grateful for.
John

[johnaboy183]

Seems like we dont appear to have any fuel pressure gurus on the forum these days. Will hang on here and hope for some expert to raise their head soon!
John