Fuel pressure creaping higher slowly

[boom3]

Aerosport IO-360B1B
Precision Silver Hawk Injection
Airflow Performance Pump
Everything 332 hours since new

My fuel pressure has always between 28 and 30 psi with the electric pump off and between 31 and 33 with it on. My Dynon "Red" range has been set to begin at 35psi. Over the last year or so every once in a while I see it go red. This happens most often when I re-start the engine after getting fuel. Often it'll teeter on 35psi and usually drops back down between 31 and 33 after runup or takeoff. Then again back down between 28 and 30 when the electric pump is turned off. It seldom ever goes red when I turn on the fuel pump for landing although it does every once in a while. More recently it has been turning red just about every time I turn the electric pump on. By red I mean it usually teeters around 36. I've never seen it higher than 37. I'm not sure what would cause it to increase over time, but it has been very gradual. I don't believe it is the sensor because it's always been pretty consistant with the electric fuel pump off.

Looking at my manual, if I'm interpreting it correctly, says the inlet to fuel pump should not exceed 35psi and the inlet to the fuel injector should not exceed 45psi.

Since the sensor is connected to the outlet of the mechanical fuel pump, (per the plans) I'm not sure what my pressure should be at that location. I suspect the 45psi maximum the manual references is to the injector itself not the inlet to the servo but I'm not sure.

Anyway just looking for some advice in case the pressure is creeping towards something it shouldn't be.

Thanks!

[Walt]

I'd be a little suspicious of those readings, the mechanical pumps rarely put out that much with 23-25 being the average.
I know the AFP pumps are set for 25 PSI (what does your pres read with just the electric on and engine off?)

No worry if it is a bit high, the 45 PSI max is at the inlet to the servo which is the same as the pump outlet.

[DanH]

Don't think I've ever checked a pressure sender for calibration. What's the best way to do it?

[Ironflight]

I've done course checks on oil pressure sensors using cobbled together adapters and air pressure from the compressor, but have never done a "fine" calibration check - you'd need a calibrated test gauge to get it better than plus or minus a few psi.

[vic syracuse]

Make sure your crank case breather doesn't have any obstructions.

Vic