Fuel Pressure Issues (Low)

One more thing to check - after start are Lane A volts normal? Also, what year were your pumps made?

Russ,

You stated earlier that you are getting a pressure of 44 PSI with the pump(s) running and the engine off.  That’s right on the money so I think that eliminates any filter issues.  When the engine is off, airbox and ambient pressure are the same so the Dynon is not having to do any computations to convert gauge pressure to differential pressure. That tells me that the fuel system is fine and points to a problem with the Dynon setup somewhere.  Maybe there is a calibration that Dynon tech support can help you with.  

Russ Pinder wrote:

Jeff Blakeslee wrote:

Russ, maybe you have already read this, but if not maybe it could be helpful (from page 7-31 of the Skyview Installation manual) :

The new Kavlico 150 PSI sensor (P/N 103757-000) and the legacy Kavlico 0-50 PSI fuel pressure sensor (P/N 101716-000) are the ONLY sensors that can be used to monitor fuel pressure when SkyView is used to monitor a 912 iS engine. If you use the EMS Engine Setup for the 912 iS that is available from the link above, the selection and setup is already correctly performed for you. If not, the following is required:

If using the new 150 PSI Kavlico sensor, the “KAV V2 150PSI DIFF103757- 000/503851-000” sensor must be selected for fuel pressure sensor selection under SETUP MENU > EMS SETUP > SENSOR INPUT MAPPING.

If using the legacy 0-50 PSI Kavlico sensor, the “KAV 50 PSI DIFFERENTIAL (101716-000)” sensor must be selected for fuel pressure sensor selection under SETUP MENU > EMS SETUP > SENSOR INPUT MAPPING.

Fuel pressure on the 912 iS is measured with respect to the air box pressure. To be able to display correct fuel pressure, SkyView must receive the following data: • Manifold pressure (via CAN bus from Rotax 912 iS ECU), and • Barometric pressure (via SkyView Network from SkyView SV-ADAHRS-200/201)

Thanks for that Jeff - I can confirm that those are the two sensors I have and that that is the sensor(s) that is set in the skyview and also that the manifold pressure is reading and registered by skyview as is the Baro. It's really annoying as it's only a couple of psi low! Going to check coarse fuel filter and clean manifold pressure regulator tomorrow to see if that helps. 

Problem solved - the issue was indeed the selection of the correct sensor in the Dynon as Jeff suggested. There are two sensor config files available for the same part number - one is exactly as the part number the other is the same preceeded by 'differential'. I'd simply picked the one that exactly matched the part I'd bought as had been advised by the Dynon tech support. I don't think it's too much to expect that they might have mentioned needing to select the differential map when they initially advised me that I'd need to change the sensor or that then they'd quickly spot the mistake from the full diagnostic dump I sent them after making the mistake especially as it's in the manual but hey ho! Lesson learned - RTFM and don't rely on the instructions supplied by support !! So thanks Jeff and everyone else who helped - much appreciated.

Russ,

That's great that it's solved!  The way they label the sensor choices is not intuitive, it makes it look like there are actually two different sensors - one for gauge pressure and one differential pressure.  But actually there is not, the only Kavlico 150 psi sensor you can get is natively gauge pressure (referenced to ambient pressure). When you choose the "DIFF" sensor from the list you are telling the software to apply a calculation to the gauge pressure reading to simulate a differential pressure sensor. So in this way the same sensor can provide a gauge pressure or differential pressure reading. This is possible because the Dynon unit has access to both manifold and static pressure and uses this information to adjust the reading.  A true differential pressure sensor would have an air sample tube that went to the airbox so that it could actually reference manifold pressure, but that's another subject...