I have a 91 745 Regina i purchased with a dead fuel pump that had been sitting for over a year.

Last year i picked up an Airtex Pump from Rockauto. i installed it and it did work, the problem i encountered was that the Fuel Pressue drops rapidly after you turn the car off.
In order to get the car to restart after say 30 minutes i have to turn the key to start wait a second turn it off and return to start, after this i have enough pressure to start the car and it will run fine.

I have tried a different ( USED )fuel pressure regulator, no change. i have replace the vac lines throughout the engine, no change, i replaced the Fuel Filter, no change.

What am i missing here, why wont this pressure hold with the pump off.
Should i be buying another pump?
Ive considered adding a check valve into the line but would rather do it right!