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Slow to start hot or cold

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Firstly this is on a 2005 Discovery 3 2.7 TDV6 but I thought being a common rail diesel and so sharing characteristics with other models this forum makes more sense for gathering knowledge, mods please move if you wish. 

I've already posted this on Disco3 but haven't had much by way of replies so hopefully the collective knowledge of LR4x4 will come to the rescue. 

I've recently bought the Discovery and it's always slow to start, worse cold at about 3 seconds but still slow warm, probably a couple of seconds. The battery is a new Exide one, 900cca, and turns it over fast but the time to fire is exactly the same as the knackered one it replaced. 

I've read the injector balances and replaced one so all are well within tolerances now but this made no difference. 

I would have thought glow plugs but there is no smoke worth talking about when it fires and that wouldn't account for the slow hot starting. 

EGRs have been blanked but the ECU shows there being a fault on one but I don't really see how this could cause issues?

 Wondering if the fuel pressure regulator could fail to hold pressure in the rail (I believe it should hold 100 bar engine off) so the pressure has to build before the injectors fire? Low pressure pump gives 0.4 bar ignition on which is alright. 

Other than starting it runs really well and returned 31 mpg over 650 miles of very hilly A roads last week so doesn't seem to be much wrong in general. 

Thanks in advance!


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 To carry on incase it helps someone in the future Following on from my thread about my Discovery 3 TDV6 taking longer to fire than it should I think I've found the cause. The fuel rail shows a pressure of 130 kpa (1.3 bar) engine off, my understanding is that this should be held by the fuel control valve on the high pressure pump at 100 bar. When cranking the pressure builds until at diagnostics showing about 9000 kpa it fires. This is below the injector trigger pressure but I think this is a delayed figure due to the diagnostics frame rate as once running it is about 22000 at idle. 

This seems to suggest that the fuel pressure control valve spring has weakened. Is this a replaceable part it is it a new high pressure fuel pump needed? If the latter I'll live with it taking a bit of time to fire I suspect. 

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