Thanks for your views falla's, got back to this one over the weekend. Suction on the supply side reaches 4inhg both before & after the filter. The return flow pressure is 3-4psi just before the filter on the return line. The HP pump is making 1500bar straight from the pump outlet & 1250bar at the rail (checked off number 1 injector fitting)both tested using a high fuel pressure test gauge. The live data pressure readings do not equate to the physical readings taken though so I think it appears I have either a frp sensor, wiring or control unit fault ??? time for some pin-out data I think