Thanks for the replys, before I went to deep I replaced the fuel filter and even though no dirt or water came out I was unable to reproduce the fault on 3 different road tests after. I got talking to someone that said the pick up in the tank can get blocked - have you heard of this before? The customer has the van back for the time being so I will keep you informed if it returns. On the live data the rail pressure seems to build fast even on start up and when reving the van but my tester only gives actual pressure not the desired pressure so I can't compare what the ECU wants and is getting. Would the problem with the rail control valve O rings disappear for a while like this? Thanks for taking the time to reply and hope I may be able to return the favour someday. Ronan