With the car idling, put regulated air pressure (hand pump or shop air) on the regulator and see if fuel pressure rises. That will rule out regulator and point toward the pump.
Put a voltmeter at the rearmost pump connector and either dial the base pressure all the way up or put 25+ psi of air on the regulator and ensure that pump voltage is being maintained under 75+ psi load. That will rule out voltage supply under load.
Put a voltmeter at the rearmost pump connector and either dial the base pressure all the way up or put 25+ psi of air on the regulator and ensure that pump voltage is being maintained under 75+ psi load. That will rule out voltage supply under load.
