Fuel regulator or Check valve?

Ok, first I have searched and read all of the topics on this, but let me state my problem.

Will not start, pump cycles when key turned on, cranks fine, sputters and that is all.

Another thing is when the key is turned off the pump will run for about 10-12 seconds instead of the usual 1-2. With the key off and the pump still running I can hear fuel moving from the top front of engine, maybe a spraying sound, not sure.

Fuel pressure is low, 10-15 lbs.

Do I start at the regulator or the fuel tank end?

97 Blazer, 4.3 TPI

The right way is to put in shutoff lines to isolate the front and rear of the fuel system to find out where the drop is occuring. but with those symptoms, the first thing I would do is pull the upper plenium and visually check for leaks there. It's a lot easier the dropping the tank.