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Safety Concern with Fuel Press Sender

BlackhawkSP

Well Known Member
I went flying 2 days ago. I have a 3 screen G3X touch with all Garmin goodies throughout. I noticed my fuel pressure bar graph just showed the white triangle at the top of the bar, with no number readout. Next day I pulled the cowl. I noticed when I unhooked the connector to the sensor (It's the Kavlico P4055-50G 0-50 PSI sensor). I noticed that the grommet around the wires was pushed out (more on this in a minute)?? Turned things back on & the Fuel Press was Red X'ed out as expected, so I looked at the pins on the connector to make sure they hadn't pushed back and reconnected then turned on the boost pump to check and had the same result. Disconnected the connector again and there was fuel inside the connector!! Sure enough the sending unit had failed mechanically and fuel was pushing out around the connecting pins on the sensor. With the connector unplugged I turned the boost pump back on and it was shooting out a nice stream of fuel onto the back of the engine. This is what pushed out the grommet from around the wires going into the connector. This is why you should always have the small orifice restrictor on the sending line from the pump, to limit the amount that will flow through any leak. This was dribbling fuel down my firewall for almost an hour flight. I'm posting this as a lesson learned and to remind folks that a wonky reading on this sensor might mean you're leaking fuel into the engine compartment. The Garmin guy I talked to said he's seen this before. Just a word to the wise:).

Edit: I posted this below, but here's a video.......https://www.youtube.com/watch?v=9P8PoiP7Gx8&feature=youtu.be
 
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I have a Dynon engine monitor and Dynon uses Kavlico sensors also. I would guess that if some Kavlico sensors are failing with Garmin units, they should also be failing with Dynon units.

I am very pleased with the Kavlico sensors that I have. I find they are much more accurate and more reliable than the VDO sensors I had before upgrading my engine monitor.
 
This is interesting----we hear about the Garmins failing, but not the Dynon---or did I miss i?

Tom

For my G3X installation, I bought my Kavlicos from Dynon because they were cheaper back in 2013. No idea how they compare today. They were identical parts.
 
Heinrich---kinda my point. If they are supposed to be the same senders, you would think we'd be hearing from the Dynon guys too. Unless I missed it, and I could have, seems its just the Garmin applications.
If its a pressure failure, it doesnt matter what EFIS you have.

Reference the other thread----just asking-
Tom
 
Fuel Press Safety Issue Update

As an update, I made a video and sent it to Garmin guys that were very interested in investigating this problem. All pilots should see this. The amount of leakage was way more than I originally thought. Check out the video. The manifold is mounted on my RV-10 on the upper left side of the firewall. The fuel was running down the firewall across the exhaust pipes and out the bottom for about an hours flight !! Luckily nothing lit off. The only way to stop this in flight is to turn the fuel valve off.

https://www.youtube.com/watch?v=9P8PoiP7Gx8&feature=youtu.be
 
Wow! That's a lot of fuel. I have the same sensor in my airplane but it's on the cold side of the firewall. Might have to re think that one.

Sure would like to see what the root cause of this failure is.
 
It might be worthy to note fuel pressure senders are installed in many GA airplanes such as Bonanzas under the floor in the cabin.
 
Wow! That's a lot of fuel. I have the same sensor in my airplane but it's on the cold side of the firewall. Might have to re think that one.

Sure would like to see what the root cause of this failure is.

At least you would know immediately from the smell. My firewall is sealed quite well and I never smelled fuel in flight. The sensor failed in such a way (by that I mean electrically) that the numbers were just dashes on the ENG page, so no alarms were triggered (high or low press warnings need values to trigger?).
 
more Kavliko failures

My buddy's AFS equipped RV-7 had the same thing happen a couple of years ago. The Kavliko fuel pressure sensor broke and was dripping fuel out of the connector.

Here's a video he sent me then: https://www.youtube.com/watch?v=8LG_oyxFtq8&feature=youtu.be

Fun fact though, he was heading to Bahamas on that flight and noticed his fuel pressure drop on startup. Could have been a real bad day.

Apparently there have been more failures, but they forgot to let everyone know.

FWIW, I'm using the Honeywell MLH050PGB06A pressure sensor. It seems to be better made, but who knows...

Lenny
 
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I have 2 of these sensors, I am going to replace them ASAP. Does anyone have a source for these?
 
A mechanical fuel pump has two diaphragms with a drain in between in case the fuel pump has an internal leak. Any fuel pressure sensor does not have this redundancy. This mode of failure could happen to any brand of sensor.

To mitigate this one could mount the sensor in a sealed aluminum can which would have an overboard vent line. It should have a small orifice to minimize pressure drop if the sensor opened up.

As I mentioned previously I have seen certified aircraft with fuel pressure transducers mounted in areas where it can drain in a safer area away from sources of heat. This would accomplish the same thing.
 
As an update, I made a video and sent it to Garmin guys that were very interested in investigating this problem. All pilots should see this. The amount of leakage was way more than I originally thought. Check out the video. The manifold is mounted on my RV-10 on the upper left side of the firewall. The fuel was running down the firewall across the exhaust pipes and out the bottom for about an hours flight !! Luckily nothing lit off. The only way to stop this in flight is to turn the fuel valve off.

https://www.youtube.com/watch?v=9P8PoiP7Gx8&feature=youtu.be

Wow, lots of fuel !!!
 
Fuel leak

As an update, I made a video and sent it to Garmin guys that were very interested in investigating this problem. All pilots should see this. The amount of leakage was way more than I originally thought. Check out the video. The manifold is mounted on my RV-10 on the upper left side of the firewall. The fuel was running down the firewall across the exhaust pipes and out the bottom for about an hours flight !! Luckily nothing lit off. The only way to stop this in flight is to turn the fuel valve off.

https://www.youtube.com/watch?v=9P8PoiP7Gx8&feature=youtu.be

Larry: Was there a small dia orifice installed? Thanks

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
Would never have known about this had I not been on this forum. When dynon/garmin issue a SB, how does it get to the customer?
 
Would never have known about this had I not been on this forum. When dynon/garmin issue a SB, how does it get to the customer?

You have to go to their websites. I don’t know why you have to register if you’re not going to get at least an email from some companies.
 
Thank you Larry!

Larry, Thank you for posting! I will check mine ASAP. This is a very dangerous situation. You may of saved an accident with this post. Knowledge is power! Thank you!!
 
Would never have known about this had I not been on this forum. When dynon/garmin issue a SB, how does it get to the customer?

Dynon sent me an email about it. I got one from Van's shortly thereafter ...
 
Larry: Was there a small dia orifice installed? Thanks

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Don:

Yes, per the plans/drawings for the RV-10, the VA 128 restrictor was installed per Drawing FF4-3. This is the same diameter orifice though, that is used for the oil pressure sensor port too, per Drawing FF1-4. I plan on calling Van's to see if there might be a different part made specifically for the fuel sensor port with a much smaller orifice port to minimize the flow rates available for a failure of the pressure sensor in this scenario. This would mitigate the fire hazard quite a bit from the current flow rates I have observed. We just need to read the pressure, so a much smaller opening would probably do to read pressure with a slight delay, while really reducing the flow rates in a failure of this type. I may just modify the one I have by plugging it with brass, and re-drilling a smaller hole.
 
I wish Garmin, as big as they are, would follow up the same way ASAP.

After I called Garmin about this, I didn't think much about it, except to let them know. The next day, I got, I think 3 or 4 phone calls from Garmin folks. One call had 4 or 5 guys on the line at Garmin, some of them their engineers, very interested about this failure I had. They appear to be all over this problem trying to sort the root causes, and prevent future occurrences of this. One guy said that they are talking to Kavlico about all this too. They also sent me (free), a replacement sensor that is the Kavlico P4055-5020-3. This sensor is the 0 to 75 PSIG certified version that has a higher working pressure and burst pressure rating. I have been pleasantly surprised that Garmin, and Dynon have been so responsive to this. That speaks volumes of their support to the Aviation community.
 
Larry, Thank you for posting! I will check mine ASAP. This is a very dangerous situation. You may of saved an accident with this post. Knowledge is power! Thank you!!

Anytime Bro!! Aviators help each other !! That's what we do:).......
 
Don:

Yes, per the plans/drawings for the RV-10, the VA 128 restrictor was installed per Drawing FF4-3. This is the same diameter orifice though, that is used for the oil pressure sensor port too, per Drawing FF1-4. I plan on calling Van's to see if there might be a different part made specifically for the fuel sensor port with a much smaller orifice port to minimize the flow rates available for a failure of the pressure sensor in this scenario. This would mitigate the fire hazard quite a bit from the current flow rates I have observed. We just need to read the pressure, so a much smaller opening would probably do to read pressure with a slight delay, while really reducing the flow rates in a failure of this type. I may just modify the one I have by plugging it with brass, and re-drilling a smaller hole.

McMaster-Carr has gauge dampers in both brass and stainless in several sizes, which includes 1/8 NPT. I have found that 0.004 works well for manifold pressure, 0.008 for fuel and 0.015 for oil. The VA-128 is shown with a 0.040" orifice for comparison. The old Kavlico's are brass, the new ones are stainless, and if you are using UMA, which I have, they are stainless as well.
https://www.mcmaster.com/3820K26

Aside from restricting flow in the event of a leak in the sensor, their real purpose is to snub pressure oscillations and provide a nice, stable read out for the monitored system, which these do well.

If you're looking for an alternative, UMA is a solid product and made in Virginia by some really nice folks with a good catalog of sensors. Most of their line is for certified aircraft, so a little more money, but it's a really small cost in the overall budget for what it does.
 
Good result eventually

I first posted this issue in 2017. After 6 months and 80 hours operation. Garmin Australia flatly refused a warranty claim because the sender was over 12 months old having sat on my shelf during the build. There was no follow up.

I'm glad the issue has now been fixed. However they should have treated the issue more seriously in 2017. We are lucky there have been no fires. We all learn lesson along the journey.

Alan
 
McMaster-Carr has gauge dampers in both brass and stainless in several sizes, which includes 1/8 NPT. I have found that 0.004 works well for manifold pressure, 0.008 for fuel and 0.015 for oil. The VA-128 is shown with a 0.040" orifice for comparison. The old Kavlico's are brass, the new ones are stainless, and if you are using UMA, which I have, they are stainless as well.
https://www.mcmaster.com/3820K26

Aside from restricting flow in the event of a leak in the sensor, their real purpose is to snub pressure oscillations and provide a nice, stable read out for the monitored system, which these do well.

If you're looking for an alternative, UMA is a solid product and made in Virginia by some really nice folks with a good catalog of sensors. Most of their line is for certified aircraft, so a little more money, but it's a really small cost in the overall budget for what it does.

Excellent info !!! Thanks. Dampening out the pulses definitely would reduce stress on the sensor, and have the added benefit of lower flow rates in a leak type failure.
 
fuel servo

Which fuel injection servo are you guys using on the planes that had a pressure sensor failure?
Something weird is happening on this RV-7 with an Avstar injection servo. After shutdown with the mixture at ICO the fuel pressure keeps going up until it gets over 50PSI and out of the range of the sensor. Who knows how far up it goes.

This doesn't happen on my RV-10 with a Precision RSA servo. This pressure rise may have something to do with the pressure sensor failures.

Lenny
 
Which fuel injection servo are you guys using on the planes that had a pressure sensor failure?
Something weird is happening on this RV-7 with an Avstar injection servo. After shutdown with the mixture at ICO the fuel pressure keeps going up until it gets over 50PSI and out of the range of the sensor. Who knows how far up it goes.

This doesn't happen on my RV-10 with a Precision RSA servo. This pressure rise may have something to do with the pressure sensor failures.

Lenny

I wonder if the pressure increase would happen if you shut off the fuel selector for 10 -15 seconds before going to ICO. Not long enough for it to use all the fuel in the line. Might be worth experimenting how long it would take to run with the fuel off to not get an increase.

A 2nd question do most shut off their fuel after shutdown?
 
+ another. I never shut mine off.

I did the Garmin SB Saturday; I have the exact numbers written down (not in front of me), but shutdown was around 23PSI, it went up 0.1 or 0.2 PSI in the first couple minutes then steadily trended downward after.
 
While I don't have that particular sensor, myself, to piggyback on Lenny's comment, I have the Avistar on my IO-390 and I do know that it holds in fuel pressure with the mixture at idle cut-off. I also have the andair fuel pump. If I park while hot, and I move the mixture off of cut-off, I can hear fuel squirt into the injectors. (when hot, of course) So I know the pressure builds and is retained in that pump-to-servo section of the fuel system.

I haven't ever had an issue, but like I said, I'm using a higher pressure stainless steel sensor. I just never heard the same thing on my IO-540 with a precision system and AFP pump.
 
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Tim-

Did you use a different sensor for a reason, or is it what was supplied with your EFIS system? Curious what you are using.
 
While I don't have that particular sensor, myself, to piggyback on Lenny's comment, I have the Avistar on my IO-390 and I do know that it holds in fuel pressure with the mixture at idle cut-off. I also have the andair fuel pump. If I park while hot, and I move the mixture off of cut-off, I can hear fuel squirt into the injectors. (when hot, of course) So I know the pressure builds and is retained in that pump-to-servo section of the fuel system.

I haven't ever had an issue, but like I said, I'm using a higher pressure stainless steel sensor. I just never heard the same thing on my IO-540 with a precision system and AFP pump.

Huh...So THAT's what I hear "squirting" under the cowl while I clean the bugs off. :rolleyes:
 
I have an ancient EFIS that uses the Grand Rapids EIS 4000/6000 as my engine monitor. They sell a couple different fuel pressure sensors, one of which is a higher pressure one that was highly recommended to me while I was building back in 2005. So I used that one, and then again on my RV-14 when I installed a similar system in 2015. I don't know the actual sensor maker, but it's a nice sensor and at least on mine I think the entire body is stainless steel.
The current website seems to show a slightly different picture from what I have though.
 
On shutdown, my fuel pressure has always climbed out of the upper limit of 50 psi. I wasn't aware that this wasn't normal until I saw the SB. Is there something wrong with my fuel servo? I run an RSA-5AD1.
 
Kavlico sensor

Just added this to another post:

I have the legacy sensors for oil & fuel pressure on my engine. Was concerned at first but no leaks since they were installed so I?m leaving them on for now. Advanced Flight Systems will have the new ones in stock in a week or so. I contacted Sansata Technologies in San Diego, the parent company. The new sensor should connect with the snap connectors on top to existing wiring harnesses.

From Sensata:

? This are using a Packard Metripack 150 connection, you should not have any issues connecting the new sensors with the existing harness.?

Regards
Aldo I. Vasquez
Field Application Engineer, North America ? Industrial Solutions



[email protected] || 619-252-7664 mobile
Sensata Technologies, 2320 Paseo de las Americas, Suite 201, San Diego, California 92154
 
McMaster-Carr has gauge dampers in both brass and stainless in several sizes, which includes 1/8 NPT. I have found that 0.004 works well for manifold pressure, 0.008 for fuel and 0.015 for oil. The VA-128 is shown with a 0.040" orifice for comparison. The old Kavlico's are brass, the new ones are stainless, and if you are using UMA, which I have, they are stainless as well.
https://www.mcmaster.com/3820K26

Aside from restricting flow in the event of a leak in the sensor, their real purpose is to snub pressure oscillations and provide a nice, stable read out for the monitored system, which these do well.

If you're looking for an alternative, UMA is a solid product and made in Virginia by some really nice folks with a good catalog of sensors. Most of their line is for certified aircraft, so a little more money, but it's a really small cost in the overall budget for what it does.

I just received the gauge vibration damper from McMaster Carr (Item #3820K42) and am now concerned about the diameter of the opening being too small and getting clogged? Anothet concern is will the fuel flow be significantly reduced with the addition of this? Do the benefits outweigh the risks? Just looking for more info to put my mind at ease. That's one small opening.

John
 
I just received the gauge vibration damper from McMaster Carr (Item #3820K42) and am now concerned about the diameter of the opening being too small and getting clogged? Anothet concern is will the fuel flow be significantly reduced with the addition of this? Do the benefits outweigh the risks? Just looking for more info to put my mind at ease. That's one small opening.

John

John,
This isn't placed in-line with the fuel flow to the engine, it is on the branched off line going to the transducer only. If I remember correctly, I think my damper is threaded directly into my transducer manifold block. Hope this helps.
 
I just received the gauge vibration damper from McMaster Carr (Item #3820K42) and am now concerned about the diameter of the opening being too small and getting clogged? Anothet concern is will the fuel flow be significantly reduced with the addition of this? Do the benefits outweigh the risks? Just looking for more info to put my mind at ease. That's one small opening.

John

The damper is to be installed (just to be sure) in the "Teed" off line to the pressure sensor block. The small orifice opening will dampen vibrations/pulses to the sensor (good thing), and will reduce the flow rate of any possible leaks. This is totally separate from the flow to the engine.
 
Clutch22 & BlackhawkSP,

Thanks for the clarification. I would have installed this inline with the Kavlico sensor, thinking that was the most logical place to reduce the vibrations/pressure. Is the damper then capped off once attached to the block?

john
 
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Clutch22 & BlackhawkSP,

Thanks for the clarification. I would have installed this inline with the Kavlico sensor, thinking that was the most logical place to reduce the vibrations/pressure. Is the damper then capped off once attached to the block?

john

Let's be clear, the vibration damper, which is essentially just an in-line orifice, is installed in a sensor line, not the main line. For a fuel line, you would have a sensor line Tee off of the supply line, or a separate line from a fuel block, if you have one. That sensor line would have the damper and end with the sensor. You could thread the sensor directly into the damper at the end of the sensing line as an option. The whole point is to dampen pulse oscillations to the sensor with the benefit of restricting flow rate if the sensor were to burst.

I want to point out that the sensor line is a static column of fluid with essentially no flow once filled, so the odds of it becoming clogged are somewhere between very low and improbable.
 
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