Slightly high fuel pressure after starting

I have the following:

Lycoming IO-360-M1B w/ stock engine-driven fuel pump; Andair electric boost pump (latest generation).

I notice a slightly high fuel pressure the last few times when starting the engine the first time...normal fuel pressure has been 29-30 psi, but lately, for the first 3-5 minutes after start-up, I'm seeing around 33-34, which then drops back down to 28-30 for the duration. This is irrespective of which tank, or whether the boost pump is on or off, or the MAP/RPMs. By the time I get to the run-up area, it's down where it has been.

What could cause this? I know it's still way below the max allowed per Lycoming's Operator's Manual (45 psi), so everything is okay, but I'd like to understand it.

The only thing I can think of is temperature ???? It's been colder here lately, could that affect it (cold in the hangar, get outside and the fuel in the tanks warms up? That doesn't seem to make much sense to me, but what do I know?)...

TIA for any thoughts on this...

Steve

Fuel Pressure

What type of indicator/transducer combo do you have. I have a carburated o-320 with Vans econo guages and they are not very stable. The fuel pressure guage is the worst.

Dynon Skyview with the stock transducers that it sold with back a couple of years ago.

It definitely appears very stable now, though...weird.

Ground

I have both the fuel and oil transducers mounted with adel clamps and must run a ground strap to the airframe. Whenever the fuel pressure reading starts acting up I clean the ground strap and all is good.

mtnflyer said:

I have both the fuel and oil transducers mounted with adel clamps and must run a ground strap to the airframe. Whenever the fuel pressure reading starts acting up I clean the ground strap and all is good.

Click to expand...

Mine are mounted using the Van's little manifold thingy that mounts on the firewall...