Nissan Repair: Fuel pump testing, fuel pump relay, haynes manual

Question
QUESTION: My son has a 1990 Sentra with low fuel pressure.  I'm trying to check the fuel pressure from the pump alone.  I have disconnected the fuel supply line going to the throttle body and inserted a pressure gauge, however when I turn the key on, the fuel pump only runs for a few seconds - pressure builds to about 10 and then drops when the fuel pump shuts off.  I would like to direct connect voltage to the fuel pump so that it runs for a longer period of time to see if the pressure increases to a normal range.  I have removed the rear seat to gain access to the electrical wiring, however, there are 5 wires leading to the tank.  I know which is the positive wire to the pump, but when I connect a hot wire to it and a ground it doesn't run.  I have been trying to find a wiring diagram for color coding of the 5 wires because evidently, I'm hooking up the wrong wires.  Any help would be most appreciated.  Thank you.

ANSWER: Ron,

Nissan uses progressive voltage to control the fuel pump and pressure.  Do, not bridge the wires to obtain a longer run for the pump.  The pressure buildup is normal and it cuts of the pump when operating pressure is obtained.  If the pressure is low at the throttle body, which it appears it is, then you have a plugged fuel filter or a defective pump or regulator.  A Haynes Manual has the wiring diagram for your car and costs about $20 bucks.

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QUESTION: Thank you for responding to my prior question.  I did check the voltage at an electrical connector leading to the fuel pump - it showed 12 volts, so I just presumed that applying 12 volts directly to the pump would make it run.  I'm just trying to see how much pressure it builds.  I have a Haynes manual for the vehicle, however the wiring diagrams do not show any wires or circuits to the fuel level sending unit or the fuel gauge - which are part of the five wires running to the fuel tank.  The Haynes diagram only shows a fuel pump relay between the hot side and the pump.  It just stumps me why it won't run when I apply voltage directly.  Can the Haynes diagram be incorrect? Do you have any other suggestions where I might be able to find a complete wiring diagram? (The Autozone website has the same diagrams as Haynes)  Thanks again.

Answer
Ron,

nissantechinfo.com is the official site of Nissan and has all the factory service manuals.  $20 bucks for each hour of access.  Just set up an account.  If memory service me correctly the five wires are a ground, two wires for the sender and another two for the fuel pump.