What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Safety Concern with Fuel Press Sender

Safety concern with fuel pressure sender

Ran the Garmin SB test on my hot engine and like some others, fuel pressure spike was essentially non-exsistent. Went from 25 psi at shutdown up to 25.2 in a few seconds, then decayed slowly to 10.4 over 5 minutes. This configuration is not at risk. In my case, Airflow Performance Silver Hawk EX on a stock Van?s YIO-540 with a fuel system plumbed per the drawings, no parts substitutions.

However a couple reports have been that fuel pressure had pegged the indication at 50 psi, including a friend?s RV-14. This is the limit of the reading and the pressure rating of the sender. Where actual pressure went is unknown and we now know that it has gotten high enough to fail the sender in a couple cases. The fuel configuration that causes this must be very ?tight? with no internal leakage. The fuel gets hydraulically locked in, heats up following shutdown, and pressure builds until something gives.
 
A friend of mine sent me video a week or so ago. You could see at shutdown that the fuel pressure rose up to 50psi and then stopped reading beyond that. So I'm sure it all just depends on what other components are all in your system. Some are probably tighter than others. Of course, if you're willing to put "crack mixture open .5" on your shutdown checklist, the fuel pressure sender will be saved. But, that may lead to more fuel in the cylinder that could cause a fire, if you accidentally have a hot mag. So pick your poison.
 
Easy?

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

Given this information, are we expecting the new sensors to be a simple plug and play swap? Disconnect and spin off the old sensor, apply thread sealant on the new sensor, torque into the manifold, and then reinsert the old plug and go fly? No other parts or changes to EFIS settings?
 
Answering my own question

Given this information, are we expecting the new sensors to be a simple plug and play swap? Disconnect and spin off the old sensor, apply thread sealant on the new sensor, torque into the manifold, and then reinsert the old plug and go fly? No other parts or changes to EFIS settings?

Went to the hangar today to do the Kavlico install.

Removed harness, spun off oil and fuel sensors from manifold, applied thread sealant to new sensors and spun them on. Old harness snapped into new sensor and wire colors were consistent. Fired up the engine which ran normally but I noted 8 psi fuel pressure (versus normal 23 psi) and alarm bells were ringing. Figured it was a setting issue and not an actual fuel pressure issue so I went into admin settings on the EFIS (*Please note, I have the AFS 5000 series original units, not touch screens so this information is applicable to legacy/non-touch users only) to change sensor name/settings but the new 0-150 psi Kavlico sensors are not an option. Spoke with Rob Hickman at AFS (who called me within 60 seconds of me sending a text...on a Saturday!) and he said to ignore the name (line #11) but go into line #13....?AD Adjust (ALL)?... and change the numbers to the following:

Display (PSI) ????? AD Value
0.0. ??????? 500
100.0. ??????- 3167

Save the settings and you should be good to go. This sorted out the issue and all is flight ready.
 
Went to the hangar today to do the Kavlico install.

Removed harness, spun off oil and fuel sensors from manifold, applied thread sealant to new sensors and spun them on. Old harness snapped into new sensor and wire colors were consistent. Fired up the engine which ran normally but I noted 8 psi fuel pressure (versus normal 23 psi) and alarm bells were ringing. Figured it was a setting issue and not an actual fuel pressure issue so I went into admin settings on the EFIS (*Please note, I have the AFS 5000 series original units, not touch screens so this information is applicable to legacy/non-touch users only) to change sensor name/settings but the new 0-150 psi Kavlico sensors are not an option. Spoke with Rob Hickman at AFS (who called me within 60 seconds of me sending a text...on a Saturday!) and he said to ignore the name (line #11) but go into line #13....?AD Adjust (ALL)?... and change the numbers to the following:

Display (PSI) ????? AD Value
0.0. ??????? 500
100.0. ??????- 3167

Save the settings and you should be good to go. This sorted out the issue and all is flight ready.

Just got mine today from Dynon. Supposed to be a plug and play for Skyview/AFS 5600T, I will keep you posted.
https://i.postimg.cc/7LSxsJ8H/20200530-174055.jpg
 
Flow restrictors

Just checking - shouldn't we place these in the sender lines as close to the engine side as possible, rather than at the far ends just before the transducers? It's not just leaky senders I'm concerned about, but a compromised hose...

Just ordered some -6 rivets to roll my own restrictor plugs but will probably backtrack and order from McMaster because I am not sure I can drill holes that fine with my drill index selections.
 
Dynon

I installed my 2 New sensors today - SKYVIEW. No changes to anything and my fuel pressure read 1/3 of Normal. Normal is 27, it read 9. Had to go into SETUP and select the new sensor in MAPPING. Now reads 27 as before.
 
Just checking - shouldn't we place these in the sender lines as close to the engine side as possible, rather than at the far ends just before the transducers? It's not just leaky senders I'm concerned about, but a compromised hose...

Just ordered some -6 rivets to roll my own restrictor plugs but will probably backtrack and order from McMaster because I am not sure I can drill holes that fine with my drill index selections.

Yes to your post. I saw the mention earlier of putting the snubber right at the sensor, but then you lost the protection of restricting flow at the "T" off from the pump. I added the snubber at the "T" off from the pump. That way the sensor and the line to it are restricted from full flow in the case of a leak.
 
It might be worthy to note fuel pressure senders are installed in many GA airplanes such as Bonanzas under the floor in the cabin.

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

I am curious if you had a restrictor installed in the fuel line?
 
I am curious if you had a restrictor installed in the fuel line?

The answer is yes. I installed the VA128 Restrictor, per the Van's drawing FF4-3. Since then though I added a Snubber discussed earlier on this thread to restrict the flow much more than the VA-128. I used the .008" size for the fuel sensor line. This will allow way less flow in any future leaks of the line, or sensor.
 
The answer is yes. I installed the VA128 Restrictor, per the Van's drawing FF4-3. Since then though I added a Snubber discussed earlier on this thread to restrict the flow much more than the VA-128. I used the .008" size for the fuel sensor line. This will allow way less flow in any future leaks of the line, or sensor.

Also folks, I redid the Garmin SB again today, since I wanted to land after a hot day of flying to maximize the chance of the fuel pressure going up after shutdown. At idle after the flight, the fuel pressure was 12.5 PSI after shutdown, it slowly went down to 1.5 PSI and stayed there till after the 5 minute period.

The oil pressure sensor was also nothing to worry about going from the 40 PSI at low idle to nothing at shutdown, and staying there, as expected.
 
Back
Top