Kavlico Fuel Pressure Sensor Technical Advisory

Dynon Avionics has released a technical advisory that can affect some 5, 15, and 50 PSI Kavlico fuel pressure sensors that are in the field. We want to make sure the RV-12 community is aware of this, as it can affect the 912 engine (although the few reports we've seen in the field have been on 912 iS engines).

Affected sensors can read slightly undexpected lower fuel pressures than expected as the aircraft climbs. Please read the entire technical advisory for the full details.

A few notes about this issue:

• Dynon believes the incidence of this issue to be rare in the fleet. Most examples of this sensor do not exhibit the issue in this bulletin.
• There is one very specific circumstance (fuel pressure that changes with altitude change) that indicates whether an unexpected or incorrect fuel pressure reading can be attributed to this issue with the sensor. In our experience, fuel pressure dips and rises are not uncommon to see across power, speed, fuel flow, and other aircraft configuration changes, especially when you're looking for them. These are NOT caused by the issue that is described in the service bulletin, and are usually an artifact of other characteristics of the aircraft's fuel delivery system. If you think you may have this sensor, remove the seal as indicated in the service bulletin to test. If you're still seeing the same behavior after you remove the seal, what you're seeing is not due to this issue.
• This issue has been seen mostly on Rotax 912 and 912 iS engines, but other engines that use these sensors can be affected. Pilots are most likely to notice this issue on installations where the allowable fuel pressure indication range is relatively narrow.

Thanks for posting this here.

I have actually noticed the following - fuel pressure normally runs 4-5 psi during normal ops....for easily an hour, but after the engine is warm and after a descent to landing or lower altitude followed by a full power climb, the fuel pressure drops to almost min - 2.2 psi, definitely below 3, and certainly causes me some concern.

Engine runs fine - not even a hint of a hiccup and I suspect my sensor is in the affected range from the dates provided and from when delivered.

This happened today on climb out from Sedona - did my first out of test cross country and no psi hiccups to, and out of Sedona, the runup and everything was fine, but a 1000-2000 AGL the FP slowly dropped to 2.2 PSI.....then slowly returned to normal.

Rubber insert in the fuel pressure sensor

At Oshkosh at the Van's Forum talk, a factory engineer speaking about the RV-12 mentioned that a purple spacer (looks like a ring with ridges) that might have been left inside the fuel pressure sensor assembly, may be causing these issues. Referred to it as the purple plug. I recall him recommending that it be removed. I had expected a formal notice to that effect from Van's that I've not seen to date. Probably should check through latest KAI and/or maintenance manual.

Upon arriving home I found the plug in my own sensor and removed it. Since then I've not seen any of these transient fuel pressure drops when decending from altitude.

That's the environmental seal. It's supposed to be there, it's just not supposed to form an absolutely perfect seal, given the design of the sensor. On most sensors, we do think it vents, but removing that seal is the test we talk about in our bulletin. You can opt to leave it removed to ensure adequate venting, and that's probably what the engineer (likely Rian?) was talking about.

Replaced Kavlico Fuel Pressure Sensor

Wanted to post a followup on the fuel pressure sensor issues I've been having. Probably should have dealt with this a while ago but in recent weeks the reliability of the sensor has been deteriorating and needed to be replaced.

The serial number of my sensor was not in the range described in the Dynon Technical Advisory from December 2014 (i.e. manufactured between July 2013 & June 2014) According to the serial number, mine was originally manu. February 2012.

Three examples of variable readings from recent flights. Appears to be triggered most often by altitude changes (I assume the ambient pressure changes)

Red line is fuel pressure, blue line is pressure altitude.



This last flight was most concerning. On climb out, fuel pressure dropped into yellow range. All other engine parameters were unaffected so I continued the climb and the fuel pressure reading eventually recovered.


I provided Dynon these charts and within 1 business day they contacted me to confirm my address to provide me a replacement/exchange. Part arrived within a week and I'm sending the faulty sensor back this week. Kudos to Dynon once again. Excellent customer service....they could teach Rotax a lesson or two.

PilotBrent said:

Wanted to post a followup on the fuel pressure sensor issues I've been having. Probably should have dealt with this a while ago but in recent weeks the reliability of the sensor has been deteriorating and needed to be replaced.

Click to expand...

Good to know. I guess I should call and get a return going too....mine was also a little like yours - slightly before the recall period, I removed the purple gasket and it has mostly been operating just fine.

About how many hours was the final deterioration?

111 hours TACH, 139 Hobbs. Looked reasonably good last summer after removing the purple gasket, but going back into my data logs, it was clearly deteriorating for last 30 hours or so.