Fuel system issue?

[240sxowner]

Alright got a question. So im driving my 240 s13 SR blacktop around town, its driving fine for about 15 mins. Then it died at and intersection and wouldnt start, had to push it into a gas station. Let it sit for a min and then it started right back up and drove fine until i got home. I just changed the fuel pump and it said it was getting 40+ psi fuel pressure, but when it was sitting at the gas station it said it was only at about 20. Does anyone have any ideas what the issue could be? All info is appreciated. Thanks in advance!