Hello Allen,
That's a "Roger" on the mechanical fuel pump.
Which brings up another question about the regulator/pump combo. Could the input pressure to the regulator be bleeding through the regulator after shutdown?
This would require a return line to negate....
To amplify: the pump produces more than three psi, a higher pressure than your regulator setting. Say the pump is actually producing six or seven psi. Could the regulator be allowing part or all of the seven psi to bleed through it after the engine stops? Not sure how you could tell whether this happens or not, though, unless you monitor the input pressure to the regulator too. It wouldn't take much volume to bleed the pressure down since gasoline is essentially incompressible; perhaps a drop or two. Unless there is a gasoline hose somewhere that expands under three or seven psi, then relaxes after shutdown.
To put it another way, could the regulator quit regulating after the engine stops?
Still a puzzle.
Tom