Jaguar S Type 2.7 fuel pressure. What should it be with engine NOT running?

Does anyone know what the fuel rail pressure should be BEFORE starting the engine?

I've had 3 years of continuing problems with cold starting (not just in cold weather) with my 2.7 S Type,

Whilst attempting to find the cause I have just replaced the fuel pressure sensor on the fuel rail at the back of the engine. It is awkward to access due to limited space for both hands. However, I managed to replace it and....it's far worse than it was before.

Let me first say that the part number of the removed sensor is 55PP04-02 and the replacement is 55PP04-01.  (It is virtually impossible to read the part number when the sensor is on the car)

My icarsoft  i930 code reader Live Data has given me the following readings.

Prior to the change of sensor my fuel rail pressure (with engine cold, not running but with ignition on) the rail pressure was reading 210 KPa. Sometimes it would read 430KPa and other times it would read 0KPa that occasionally flashed up to 40KPa as I watched it. This is why I decided to change the sensor as I suspected this may be the cause of the erratic starting crank times.

With the new sensor fitted the non running cold engine sensor reading are madly fluctuating around 18000KPa...................When I start the engine the pressure stays around 18000KPa but after 20 or 30 seconds the engine cuts out and the icarsoft i930 displays Fault codes re fuel pressure being out of range.

It seems that the sensor number must be exact in order for it to work correctly.