Make sure there's enough voltage going to the fuel pump from the relay. Double-check the ground connection. Use a multimeter instead of a test light to make sure you got good voltage and ground. Then, check the fuel pressure before the pressure regulator. If there's still not enough pressure, check pressure before the fuel filter. If there's still no pressure, the problem could be the fuel pressure relief valve in the pump assembly is stuck open or there's a problem with the pump itself, or the mesh filter to the pump, possibly an obstruction.