L322 Cranking But No Start

Hello
How's everyone?
I have a RR L322 4.4 V8 Petrol 2003 my issue is that I changed the battery and the car started and ran but 5 mins later it stopes and now will only crank and not fire up.
I have checked fuel pump relay and jumped pins and I can make pump run but still no start. I have isolated power to LPG system and still nothing. I can also only assume the injectors are not going either... I'm a bit stuck on what to try next. Ecu reports no faults by the way.
Thank you in advance any help is great
Craig

Whilst pump may be heard running - it may not be producing pressure.

Remove the acoustic cover on the top of the engine and on the fuel rail you'll see a schreider valve - Using a cloth to catch any spurts of fuel, press the valve in and see if there is fuel pressure. May need to give it a crank then do it, or get someone to crank it while you check it....remember this will be fuel at high pressure, so be cautious!