Intermittent erratic fuel pressure indications - Kavlico sensor?

[sunfish]

I have a 912 iS and the latest Kavlico fuel pressure sensor. I am receiving erratic fuel pressure readings from zero to 70+ psi. This happens for periods in flight but I have not been able to reproduce it on the ground.

I am satisfied that this is a gauge issue and that fuel pressure is rock solid. The fuel pressure regulator and fuel filter was replaced without the behaviour changing and engine performance + EGT’s, fuel flow, etc, do not change when the dancing pressure indication starts.

As far as I can tell, I have continuity in the wiring. What am I missing?

 

[swatson999]

Need more info. How often in flight? How long does it last? Do you have plots of these data (e.g., SavvyAnalysis)? Why are you convinced it's the "gauge" (do you really mean the gauge, or do you mean the transducer), instead of perhaps cavitation in the line, etc.?

 

[sunfish]

Thank you for your post. The erratic behaviour lasts for a few minutes, then stops and perhaps restarts. I have not been able to duplicate it.

The fuel system is as per plans and performs that way and has done so since construction. The fuel pumps are pressurizing a common rail fuel injection system via a high pressure filter, exactly as Rotax requires. The fuel pressure regulator and high pressure filter have been replaced with no effect. The engine runs fine without missing a beat when the indication goes haywire - no change in rpm, no change in EGT or fuel flow. The fluctuation seen is from 70 psi to zero. Specified figure is around 44 psi. Changing pumps or running with both makes no difference. The fuel tank state makes no differenc. The sensor is the latest as specified by Dynon and has been replaced by Dynon once when the zero pressure point changed.

‘’I am left with the conclusion that I have a wiring issue of some kind or perhaps an EMS issue.

 

[Markf]

I had similar issues with my fuel pressure ! Replaced the sensor and the problem went away.

 

[Rhino]

From what I've seen, difficult intermittent issues like this with fuel pressure readings are primarily caused by the sensor, followed by the transducer or wiring problems not detectable on the ground at low or zero RPMs. Occasionally it's the gauge, but not so much when the problem is intermittent. Those usually just fail completely. These are only observations based on the reports of others, mind you. I have no direct experience with these problems, and I am in no way claiming to be any sort of expert.

 

[fastfred58]

I have a 912 iS and the latest Kavlico fuel pressure sensor. I am receiving erratic fuel pressure readings from zero to 70+ psi. This happens for periods in flight but I have not been able to reproduce it on the ground.

I am satisfied that this is a gauge issue and that fuel pressure is rock solid. The fuel pressure regulator and fuel filter was replaced without the behaviour changing and engine performance + EGT’s, fuel flow, etc, do not change when the dancing pressure indication starts.

As far as I can tell, I have continuity in the wiring. What am I missing?

Check your fuel filters are clean I also removed the sensor and found a fine film on the screen but you can only rinse it and wipe it no air pressure. New Fuel filter seemed to correct it.

 

[swatson999]

Intermittent and erratic indications usually mean a bad ground. For the *old VDO* transducers, those would fail with this sort of behavior, but I don't the the Kavlicos do. I'd check my ground wires and connections first.