Mark
Thanks for the info, I will try the KOEO test.
When the fault occurs the pressure in the pipe to the gallery is very low and takes 20 seconds to build up to 3 bar before it fires.
The fault will only seem to happen if the engine has reached operating temperature before being left overnight. When we started testing we couldn't get the fault as we were just driving in and out of the workshop.
Ive run a clear pipe from the fuel filter to the tandem pump ,to check for air, and air does appear in the pipe, only after we get the non start fault.
I will let you know how I get on with the other test.
Regards
Joe