95 Fuel pressure 3.8L

I did the key on, ignition off test yesterday and the pressure was reading about 18 psi, should be about 40 psi. I turned the key on a few times and it builds up pressure and holds at the required specs, but why wouldn't I be getting proper pressure on the first activation of the fuel pump and shouldn't I?

The system seems to be running a little lean (temp range changes drastically between driving (cool) and idling (hot) in traffic). Anyone know what might be causing it? It doesn't maintain a constant range other than from one extreme to the other with the fans kicking on to cool things down when at idle. My thoughts are that it is running lean and that's causing the temp problems.

I do have fuel pressure within range when at idle and it spikes when I remove the vacuum line to the regulator.

All good suggestions are appreciated, Thanks.

Best guess is that the check valve that holds pressure in your system is not sealing, causing the pressure to drop when the pump is off. A few key cycles will clear this up. I doubt it's related to an erratic temperature. When you say erattic temps - are you using a scan tool, or the guage on the dash? I'd check the sensor first. If no scan tool, Try removing the connector on the sensor and putting it in FMEM mode, and see if the readings stabilize. If yes, your sensor might be bad.

The pressure isn't dropping, the initial pressure on the first "key on" the pump isn't getting the fuel pressure up to proper pressure (18 PSi), but if I cycle the key on a few times, it will build up enough pressure and it maintains the pressure (45 PSI). It's just the initial key on that seems to be a problem being low from the start, it never gets up to pressure on the first key on. Since I understand this to not be normal, I was wondering what might fix it and if it might be causing the car to run lean.

The temp fluctuates from low normal to high normal, but high high normal when idling in traffic and the fans kick into high gear. Was thinking it might be running lean, causing the car to heat up too quick, the engine stumbles a little when it gets to high normal also.