I still get 20-22mpg, and from what I've read, my fuel economy would suffer if the FPR was bad?? Is that always true?

AC Delco fuel pump is 2 years old and the vehicle sat for over 12 months until february. I've had hard starts for a while due to lack of fuel pressure maybe 85% of the time, regardless of how long my blazer sat. Sometimes it sits all day and starts right up; sometimes it sits 2 minutes and needs to be primed twice. Runs good after it fires.


I'm suspecting the check valve in the pump assembly and not the FPR???
Any way to know besides "clamping the lines and checking pressure?" I don't want to clamp my fuel lines =). I'm hesitant to pull apart the upper intake and not find anything obviously wrong.

Would installing a 1/2" spring check valve with 3/8" hose barbs be a worthy solution? My fuel lines are already hacked with fuel injection hose clamped to new steel pipe, so adding a check valve is simple.