Higher fuel pressure when cold OAT?

[lr172]

Originally Posted by Jcurry

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.

[Mich48041]

Rubber expands when cold. But who knows what the diaphragm is made of.

[lr172]

Originally Posted by Mich48041

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.

[IlliniRV12]

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

[Jcurry]

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.

[IlliniRV12]

Thank you Jack I will see if I can find it tomorrow.

Jerry