1998 For Explorer Sport, 2WD, 4

1998 For Explorer Sport, 2WD, 4.0, OHV, 243,000 miles. It stalled and will not restart. No check engine light. PCM fuse and Fuel pump relay (it clicks) and fuse and are good. Fuel pump hums when ignition key is turned on (heard loud with my ear next to open gas cap or listened to a hose inside tank while I’m cranking it). Fuel shut off switch is not tripped. After turning on ignition key several times engine will attempt to start. No fuel pressure on test gage during cranking. A small amount of fuel without pressure came out when the fuel injectors test port is pushed. Bypassed fuel pump by introducing fuel to the intake manifold via brake booster hose and engine starts and stays running. Replaced fuel pump with Airtex and filter 2 years ago due to hard start in the morning and when parked over 4 hrs. (Cause was fuel pump check valve stuck open with debris allowing fuel in the fuel line and manifold to drain back to the tank). Why would it be the fuel pressure regulator if no fuel comes out? Could it be that the fuel pump has gone bad that early because it could have got clogged? I cleaned the tank then. I keep the tank at least ¼ full. I think it is the fuel pump but don’t want to replace it unless I can’t find another cause. Any advice would help. Thank you.