Check the pressure at the regulator and see if it is there. Is there any chance there is a little crud in the check valves that could allow some seepage back? Apparently they need the two pumps in series to provide the pressure required. Two last things I can suggest.
1) turn the key on and listen for the electric pumps to cut in -when they reach proper pressure they will shut off. THEN try to start the car.
2) Take you two pumps in and have them checked for volume and pressure output.
I have a feeling that your problem will be somewhere in the circuit between the pumps and the regulator.