2003 X5 Diesel [Australia] heat related issues?

[thelostboss]

I have a 2003 diesel X5, recently purchased with 400K plus on the clock but well maintained. It runs really well except when in stop-go traffic in hot weather conditions and has had occasional reluctance to start on first turn of the key when it has been run for a while. Yesterday however it became much worse. Car had been driven for around 190 km on a day of temps in the high 30s [celsius] when it threw a low coolant warning, coolant level when checked was fine. On the return journey it first gave a "check oil level" warning, followed some time later by a "low oil pressure" warning. The oil level was checked and was fine. These warnings only appeared when stationary and shifting to neutral cleared them from the display. The car was then parked for around 15 minutes and at that stage it would turn over but would not fire. I happened to be outside a Mercedes mechanic at the time and he plugged in his computer [despite being officially closed at that time], the only error showing was related to "fuel rail pressure" - I did not see the display and so cannot be more precise than this. After around another 45 minutes cooling-off it started perfectly as if nothing had happened at all.


I am thinking that it might be an electrical heat-related issue with one of the ECUs [coming from a Land Rover background] or possibly fuel pump or injector related.


Any suggestions would be gratefully received. I have ordered some diagnostic software and cables in order to set up my own diagnostic system, but that will not be here for some weeks; and summer will be here before then!


Cheers
TLB