To answer for once the truck is started.
Once the motor is started, the pump runs full time so the pressure gets up high enough.
Then at shutdown, the check valve in the pump holds the pressure for some amount of time before bleeding off, so a hot restart may not show to be a problem.
The proper way, though few ever do it, is to measure the pump flow rate or volume to determine if the pump has an issue.
Once you think a bit about it, pressure is not the only factor, but flow rate under that pressure has to be up with it.
The reason is the pump line pressure will rise if you squeeze off the return {but} the volume flow rate goes down. It's an inverse function.
Same as putting your finger over a water hose to increase the exit pressure. The amount of water coming out per unit of time is reduced.
For the fuel pump, the pump's capacity and line size determined by design is the sole control of pressure and volune at a specified design operating voltage.
Good luck.