What's new
Van's Air Force

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

Higher fuel pressure when cold OAT?

Jcurry

Well Known Member
Hello,
My fuel press is going too high and triggering the alarm on my Dynon D180. This has been happening since we dropped into the 30s. I don't if this is temp related or if the fuel press xducer is failing on me. I suspect the latter. I'm sure I have the old school xducer. My xducer is mounted on the fire wall.
What do you think? Thanks.
 
quite unlikely that cold temps would make any meaningful difference in fluid pressure sensor readings. An exception would be a sensor that is failing inside, but only acting up / showing symptoms when cold. That is not uncommon. The old diaphragm style sensors (transducers are solid state) do not last forever and not uncommon to fail early. Sensors have only two connections (sometimes only one connector and grounded via the threads) and transducers have three (almost never grounded via threads).
 
Last edited:
Temp Related

Hello,
My fuel press is going too high and triggering the alarm on my Dynon D180. This has been happening since we dropped into the 30s. I don't if this is temp related or if the fuel press xducer is failing on me. I suspect the latter. I'm sure I have the old school xducer. My xducer is mounted on the fire wall.
What do you think? Thanks.

Once the engine is warmed up does the alarm go away? If not, I would surmise that the sender is warmed enough by the engine to point to a bad transducer.
 
+32F

At +32F water may freeze.
Depending on where the xducer is located in the system this may
show up as high or low pressure.

Good luck
 
quite unlikely that cold temps would make any meaningful difference in fluid pressure sensor readings. An exception would be a sensor that is failing inside, but only acting up / showing symptoms when cold. That is not uncommon. The old diaphragm style sensors (transducers are solid state) do not last forever and not uncommon to fail early. Sensors have only two connections (sometimes only one connector and grounded via the threads) and transducers have three (almost never grounded via threads).

Hi Larry,
I agree with everything you said. I was using the term transducer loosely. Thanks for your reply. I now have a fuel pressure sensor and oil pressure sensor on order.
 
Once the engine is warmed up does the alarm go away? If not, I would surmise that the sender is warmed enough by the engine to point to a bad transducer.

Hi CT,
Thanks for your reply. I also believe the sensor is failing.
 
fuel pressure sensor and oil pressure sensor

I too had a high fuel pressure alert on my Dynon D180 yesterday in cold weather 24 degrees. If you replaced the fuel pressure sensor and oil pressure sensor did it fix the problem and where did you purchase them from?

Jerry Kewanee Illinois
 
I also noticed high fuel pressure readings in the cold weather here in Dallas. Wasn’t that cold around 30’s. Newer build with only 45 hours. May look into replacing as well.
 
I too had a high fuel pressure alert on my Dynon D180 yesterday in cold weather 24 degrees. If you replaced the fuel pressure sensor and oil pressure sensor did it fix the problem and where did you purchase them from?

Jerry Kewanee Illinois

Hi Jerry,
I'm "winging" this but in conjunction with what Larry said above, I suspect the diaphragm in older sensors are less pliable and stiffen considerably in colder temps producing higher readings. That's my theory...
My parts have not arrived yet. They are due in tomorrow. I ordered the sensors on Amazon.
Fuel Sensor 360-043 0-30 psi $58.16
Oil Sensor 360-430 0-150 psi $71.42

Of course it's warming back up here in Florida....
 
Last edited:
Hello Jack

It's 54 degress in Illinois right now all the snow has melted. Thank you for quick your response. My annual is coming up next month so I will have plenty to do, thank you for the part numbers. Jerry
 
Hi Jerry,
I'm "winging" this but in conjunction with what Larry said above, I suspect the diaphragm in older sensors are less pliable and stiffen considerably in colder temps producing higher readings. That's my theory...
My parts have not arrived yet. They are due in tomorrow. I ordered the sensors on Amazon.
Fuel Sensor 360-043 0-30 psi $58.16
Oil Sensor 360-430 0-150 psi $71.42

Of course it's warming back up here in Florida....

The fluid pressure exerts force on the diaphragm. As it moves due to this force, an arm connected to the diaphragm slides over a carbon trace providing incremental resistance. A stiff diaphragm would resist the force more than normal and should produce a lower pressure reading. Rubber that is weaker than normal would resist less and produce a higher reading and this is the typical failure mode. I believe the cold temps are creating issues in the mechanical attachment to the POT or the pot itself and not the diaphragm.
 
Last edited:
Rubber expands when cold. But who knows what the diaphragm is made of.

It is made of rubber. That said there are countless variations of "rubber." While it might expand when cold, it also gets stiff when cold. These sensor generally work off the principle of the rubber diaphragm expanding in a convex fashion due to the fluid pressure. The center of the convex shape is attached to something to measure it's linear movement that can correlate the movement to pressure level.

If the expanding rubber was adding errors, you would be seeing something other than 0 with no pressure when cold.
 
Last edited:
fuel pressure sensor

Hello Jack

I was wondering if you installed your fuel pressure sensor. My annual is being done now and I did buy a fuel pressure sensor. Did you get yours installed and where is it located if you wouldn't mind? A picture would help if you have one.


Thank you Jerry
 
Fuel pressure sensor.

I did replace my fuel pressure sensor. Mine is located on the LH firewall near the oil pressure sensor and the brake reservoir.
I believe the original location was near the front of the engine by the mechanical fuel pump. Previous owner relocated it.
 
Back
Top