1990 Ford Bronco

Engine Mechanical problem
1990 Ford Bronco V8 Four Wheel Drive Automatic 131000 miles

When first starting the engine the fuel pump doesn't stop running after a few seconds like it's supposed to it's like it is not building pressure I checked it at the fuel rail port it was 40lbs I have changed the regulator and all relays, also the filter and checked the fuses. Any suggestions on what it might be?
September 8, 2009.

Have you checked fuel pressure drop off? That is when you shut the power to the pump. It should hold pressure for a certain amount of time.

Let me know.