Originally Posted by
njones
Thanks for the help. We have not resolved the issue 100% but we did satisfy ourselves that it was a measurement issue, not an actual low fuel pressure. We did a couple of full power climb tests over the airfield in Pampa TX where we stopped to check it out and although the fuel pressure showed extremely low the engine exhibited absolutely no signs of running lean at all. There was no fuel leakage from the drain hole in the fuel pump and no other visible signs of a problem.
When we observed the fuel pressure go from normal - then very low, then back to normal within 10 minutes at cruise with zero changes in engine parameters we concluded that it had to be a measurement issue.
Water in the sensor line is on the "to-do" list to check along with all sensor wiring back to the EFIS and ground before replacing the sensor itself. I guess removing the sensor and letting the line bleed a bit with the tank head pressure should clear out any thing that ought not to be there. We did not observe any unusual readings in the second half of the trip - so maybe any contaminants in the sensor line has bled itself out?
P.S. total flight time from Moriarty NM (just east of Albuquerque) to Kitchener, Ontario Canada was 12.6 hours - with fuel burn averaging around 4.3gph - and indicated airpseed of 130-135kts.