I wonder if the capillary between the fuel servo and the pressure sensor is inadequately sized causing vapor in the system? Another thought is the location of the sensor directly connected to the servo. Many airplanes have the sensor on a T off of the fuel pump outlet and not on the servo. These are just guesses of mine at this point since nothing else seems to explain the issue. Unfortunately we are stuck with what Diamond gave us unless a mechanic is willing to file a 337 and change the fuel pressure pickup point. Diamond has ignored the issue within the fleet so we are on our own.
I may talk to my AMT about doing exactly this to see if it changes the indication issue. The part that would need to be added is a KB-090-T "Tee Fuel Pump Fitting" and a a modified AN823-4 with a 040" Capillary hole. I would have to plug the hole on the fuel injector also. Not a big deal but not sure a 337 covers this as a minor alteration or a major alteration. A major alteration requires an FAA sign off.
The parts look like this:
http://www.aircraftspruce.com/catalog/e ... -11908.php
http://www.aircraftspruce.com/catalog/e ... g00783.php
If anyone else has the time and the AMT that is willing to give this a try PM me and I will share my SWAG knowledge with you. It is also worth a call to Precision to ask their opinion of the location of the pressure sender.
I don't believe that Precision intended for a fuel pressure gage to be connected directly to the servo.
Rick wrote:I'm sorry for not posting back about this. A couple of months ago, my fuel pressure reading became even more erratic, both high and low multiple times on every flight. I finally disconnected the plug and applied Stabilant to the connector, and my fuel pressure has been rock-solid ever since. My mechanic said he has changed the connector on several DA40's to fix this problem, so I ordered a new connector, but I thought I'd try the Stabilant first, since the connector is so easy to get to. If the problem comes back, I'll probably install the new connector next.
I wonder if those who had success by just swapping the sensors, actually "fixed" the problem by simply removing and reconnecting the plug, thereby reestablishing a good connection again...