D4204T Cold starting problems

[Japster]

Hi,

V50 2005 2.0D

I’m looking for some advice on my quest to get to the bottom of my cold starting issues.

Symptoms:
Under 7degs C - car will start then immediately stop after about 3 seconds
Repeat about 10 times, will eventually keep running

Over 7degs C - car will start 2nd time and keep running, 1st time it nearly starts

After reading fault codes I’ve changed:
Air Inlet Temp sensor - sensor head missing, car now runs better but fault remains
Glow Plug on cyl 4 - was open circuit, car starts a little better
Glow Plug Relay - no change after this

Yesterday I tested the fuel filter pre-heater - open circuit
How critical is this? Does this only come into play in extreme cold?

I’m noticing air bubbles in the fuel line after the filter, no leaks apparent on filter housing. Could this effect cold starting? Doesn’t effect running once started

I’m thinking of buying a proper Vida/dice setup but I’m unsure if I will find out anything more from it

Any help appreciated,

Craig