Hi CTH,
there is a lot in the archives, so a search will give you a lot of info.
Pressure is normally measured at the fuel distributor in the engine comp., if my memory serves me right. For my 420, I believe its in the 60s psi area. The 2 pumps generate "system pressure" and excess fuel is sent back to the tank. Little differences in pressure are then used to fine-tune with the Electro-Hydraulic-Actuator or EHA. The check valves I guess help the pumps and the accumulator is supposed to keep the pressure up after the pumps stop. That's why Stan Pittman has his money on the accu.

190E2: When placing the car key in the position just before the start without starting, my pumps will run for about a second and built up the pressure. You might try this 2 or 3 times with your car and see if it starts better.
Good luck