Nissan Repair: Broken fuel pump Primera, fuel pressure regulator, vacuum pipes

Question
Hello :)
I have a Nissan Primera LX 93. Two weeks ago I changed my fuel pump because it was broken, I replaced it with a new one and the car was fine again. Now the NEW fuel pump is broken! I have had it out of the car and tested it. The pump is spining but it want pump. I have three questions :) 1. Can the fuel pressure regulator be broken, so that no fuel returns to the fueltank? 2. If the fuelpump is spining but can not push the fuel, won't this damage the pump? 3. What does the vacuum pipes ontop of the fuel pressure regulator do? (isn't the regulator only a mechanical device?)

Answer
Morten,

If the filter is blocked the pump will blow due to excessive pressure.  If the regulator is blocking the flow of fuel it could do it too.  But, since you replaced it and it s defective too i would assume a defective pump from the remanufacturer.  The vacuum on the pressure regulator cuts fuel pressure by dumping excess fuel back to the tank when the vacuum on the engine is high.  This indicates a no load condition and that is why the pressure is less.  When you floor it the vacuum goes away and the pressure increases to feed the demands of the engine.