91 2.5L losing fuel system prime

The fuel pressure regulator is inside the gas tank , it's part of the fuel module . No vacuum line inside the fuel tank .

The Fuel System is a returnless on-demand design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe from the engine. A returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.
An electric turbine style fuel pump attaches to the fuel sender assembly inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter and the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pump also supplies fuel to a venturi pump located on the bottom of the fuel sender assembly. The function of the venturi pump is to fill the fuel sender assembly reservoir. The fuel pressure regulator, a part of the fuel sender assembly, maintains the correct fuel pressure to the fuel injection system. The fuel pump and sender assembly contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.

pull the fuel pump and overhaul/replace it
could be dirt under valves or no power if electric

Fuel pressure regulator . plugged fuel return line .

With the ignition switch ON and the fuel pump running, the fuel pressure indicated by the fuel pressure gage should be 333-376 kPa (48-55 psi).
The Fuel Pressure Check determines if the fuel system is providing fuel pressure. The components involved include the fuel tank, sending unit, pump, pipes and hoses, pressure regulator, fuel rail, and injectors. Also checked is the electrical operation of the fuel pump relay. This chart requires J 34730-1A , Fuel Pressure Gauge J 37287 , Inlet and Return Fuel Line Shut-off Adapters.

Fuel pressure may drop due to a leaking injector or bad check valve in the fuel pump itself. The regulator does not come into effect until the engine is running and a vacuum supply is produced to it. If the regulator is leaking internally, it could send fuel back to the tank as well. Prime the fuel line and pinch off the return line ( if possible ) to eliminate a regulator problem. If the fuel pressure drops with the return line pinched off, suspect a leaking injector or fuel pump. If injector is leaking, the vehicle should run rich and cause a hard start/rough run condition

First off, do you hear the fuel pump priming when you turn on the key. Should hear a light buzzing from the fuel tank for approx. 5 seconds. Have you opened the pressure line or the pressure test port on the fuel line on top of the engine to see if you are getting any fuel even trickling out especially during the priming. Pressure should be in the neighborhood of 45-50 psi for the system. A fuel pump can slowly fail, by losing pressure, but still can move some fuel if you hear it running oon the prime cycle. You can often borrow a fuel pressure guage from your local chain auto parts store to actually see what's goin on with the fuel system. You hook it up to the test port on the fuel rail and watch the pressure on the prime cycle. If it is very low, try priming the system 3 or 4 times to see if pressure builds, if not that would lead to testing the pressure regulator. But that's for next time.

Hi, The fuel pump is in the tank. You will have to remove the tank to get at it. Good luck

to replace the fuel pump module.first you need to relieve the fuel system pressure.turn off radio first, then disconnect the negative battery cable.drain fuel from fuel tank.then then safely raise support car on jack stands. make sure sitting on solid level ground then remove the fuel charcoal canister hoses and vent line remove disconnect fuel pump. disconnect fuel pump electrical connector and remove fuel filler hose from fuel tank then remove the fuel tank from the vechicle.the heat shield and the rear exhaust system may have to be remove if you problem dropping the fuel tank.once fuel tank dropped you need snap ring pliers to remove the fuel pump module retaining ring.disconnect the fuel pump sending unit.disconnect the fuel pressure sensor and fuel pump module electrical connector .if you need help to replace the fuel level sending unit.you need a haynes repair manual.it has instruction how to remove and replace the fuel level sending unit.but most of the time the whole new fuel pump module come with new fuel level sending unit.if you are replacing fuel pump.when done put every thing back visa versa. be very careful working around gasoline and fuel tank.dont smoke.becareful dont make no sparks with wrenches when removing gas tank.wear safety glasses and have a helper at all times. dont work under vechicle by your self.

the fuel pump is in the gas tank and the fule filter runs along the bottom of the Driver side..if your looking at the gas tank follow the gas lines that go toward Eng. you will see the Fuel filter

300M, Concorde, Intrepid, LHS, 1998-2004 - Fuel Filter Removal & Installation The fuel filter mounts to the frame rail in front of the fuel tank. The inlet and outlet ends of the filter are marked for installation purposes. Install the fuel filter making certain that it is properly orientated.

NOTE The fuel filter is part of the fuel pressure regulator mounted on the fuel pump module.

1. Before servicing the vehicle, refer to the Precautions section.
2. Properly relieve the fuel system pressure.
3. Lower the fuel tank.
4. Remove or disconnect the following:
   Negative battery cable Purge and vent lines Fuel line from the pressure regulator Filter/regulator by pushing in the locking tab, turning the regulator to unlock it and pulling the it straight up

To install:




Fig. Cut away view of the fuel filter/pressure regulator

1. Push the fuel filter/regulator into the fuel pump module and turn to lock it into position.
2. Connect the fuel lines and install the tank.
3. Start the engine, check for leaks and repair if necessary.

Fuel Pump - Removal & Installation
The in-tank fuel pump module contains the fuel pump and pressure regulator which adjusts fuel system pressure. Fuel pump voltage is supplied through the fuel pump relay.

The fuel pump is serviced as part of the fuel pump module. The fuel pump module is installed in the top of the fuel tank and contains the electric fuel pump, fuel pump reservoir, inlet strainer fuel gauge sending unit, fuel supply and return line connections and the pressure regulator. The inlet strainer, fuel pressure regulator and level sensor are the only serviceable items. If the fuel pump requires service, replace the fuel pump module.

1. Before servicing the vehicle, refer to the Precautions section.
2. Properly relieve the fuel system pressure.
3. Remove or disconnect the following:
   Negative battery cable Fuel tank
4. Clean the top of the tank to remove any loose dirt.
   Fuel lines from the fuel pump module by squeezing the quick-connect fitting with thumb and forefinger
   
   
   
   
   Fig. Using special tool 6856, remove the fuel pump module locknut
   Fuel pump module electrical connector from the top of the fuel pump module
5. Using special tool 6856, remove the fuel pump locknut by turning it counterclockwise.
   CAUTION The fuel reservoir of the fuel pump module does not empty out when the tank is drained. The fuel in the reservoir may spill out when the module is removed.
6. Remove the fuel pump and O-ring from the tank and discard the O-ring.
   

To install:

1. Thoroughly clean all parts. Wipe the seal area of the tank clean. Place a new O-ring on the ledge between the tank threads and the pump module opening.
2. Position the fuel pump module in the tank. Be sure the alignment tab on the underside of the pump module flange sits in the corresponding notch in the fuel tank.
3. While holding the fuel pump module in place install the locking ring and torque to 40 inch lbs. (5 Nm) using special tool 6856 or a spanner-type tool.
4. Install or connect the following:
   Fuel tank Fuel pump module electrical connector Negative battery cable
5. Fill the fuel tank with fuel. Install the fuel filler cap. Turn the ignition switch to the ON position to pressurize the system. Check the fuel system for leaks.

Hope this helped.

Buick with a 5.0?? OK, regardless, pressure should not drop like that. Possible that fuel filter is full of **** & should be changed, or, you may indeed have a bad pump... (can happen). Sending unit: sounds like you have the leads reversed or the unit is somehow different than the one you replaced.