Fuel pump or possibly PEM

[dakinejb]

Working on a 2004.5 S40. For a few weeks it was hard to start and would give a cylinder misfire CEL once started but car would run fine after it was started. It would restart fine as long as it didn't sit more that 12-24 hours. I checked fuel pressure by hitting the vale on the fuel rail and noticed pressure was dropping as it sat. I was thinking the check vale was bad. But today the car wouldn't start at all. Is this a sign of the fuel pump going out or could it a the PEM. I no nothing about PEMs I came across them looking for answers to this problem.