Yesterday while taxing for departure the lady in the EFIS started complaining about fuel pressure. It seemed to be intermittent and I have had this indication at times before. The EFIS would read 7.5 to 8.0 # then after a bit the pressure would go back down to much lower numbers. I thought the problem was a faulty sender as the engine didn't care. Anyway yesterday after I flipped on the boost pump for takeoff the lady started complaining about the pressure again but as the power came up the pressure fell to about 7# and she shut up. I did a couple of circuits of the field. Every time power was reduced the pressure would go up and hold at 8# or so until I powered up then it would reduce.
I know how these LW 15472 low pressure pumps work as the actuator spring is the pressure regulating device so I decided to put a mechanical gauge on the fuel system. I just knew the problem had to be a faulty sender. To my surprise the mechanical gauge and the EFIS read within 1/2 # of each other. With just the mechanical pump on the pressure was generally around 7.5# and when the boost pump was turned on it jumped up to a little more than 8#.
I had always been told that there was no way for the system pressure to build that high because of the way the pump was designed. I do know now that that is just not true. The pump has less than 400 hours on it and I have a new one on the way. I never had a problem with this before I upgraded the panel and the plane was not flying for about 6 months. The pressure before always was in the 2 to 3# range and sometimes would fall below 1# for a short period.
Perhaps some folks out there in Van's land have an explanation for this abnormal behavior as I have never heard of a spring getting stronger, just weaker with time. I sure can't think of another explanation.
I know how these LW 15472 low pressure pumps work as the actuator spring is the pressure regulating device so I decided to put a mechanical gauge on the fuel system. I just knew the problem had to be a faulty sender. To my surprise the mechanical gauge and the EFIS read within 1/2 # of each other. With just the mechanical pump on the pressure was generally around 7.5# and when the boost pump was turned on it jumped up to a little more than 8#.
I had always been told that there was no way for the system pressure to build that high because of the way the pump was designed. I do know now that that is just not true. The pump has less than 400 hours on it and I have a new one on the way. I never had a problem with this before I upgraded the panel and the plane was not flying for about 6 months. The pressure before always was in the 2 to 3# range and sometimes would fall below 1# for a short period.
Perhaps some folks out there in Van's land have an explanation for this abnormal behavior as I have never heard of a spring getting stronger, just weaker with time. I sure can't think of another explanation.