If you have a Autozone or Checkers nearby you don't need to buy anything. You can just rent the fuel pressure gauge kit. The kit will have everything that you need. You will only need the adapter if you are checking the fuel pressure in-line just after the fuel pump. You wouldn't need it since you will be just checking it from the service port on the fuel rail. The service port looks just like the air valve for you tires.
This should help you out:
TESTING
See Figures 4, 5, 6 and 7
Fig. Fig. 4: Connect the fuel pressure gauge to the fuel rail service valve-3.3L shown
Fig. Fig. 5: Checking the fuel pressure with a gauge-3.5L shown
Fig. Fig. 6: Checking the pressure between the pump and the filter
Fig. Fig. 7: Place the other end of into an approved gasoline container
1.Release the fuel system pressure as described in earlier in this section.
2.Remove the protective cover from the service valve on the fuel rail.
3.Connect fuel pressure gauge to the fuel rail service valve.
4.Place the ignition key in the ON position.
5.If the gauge reading equals the specifications, then further testing is not required. Without vacuum applied to the regulator, the 3.3L engine fuel system operates at 55 psi (379 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 46 psi (317 kPa). Without vacuum applied to the regulator, the 3.5L engine fuel system operates at 48 psi (331 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 39 psi (269 kPa). The fuel system pressure varies with the different amounts of manifold vacuum applied to the regulator. If the pressure is not correct, record the pressure and remove the gauge.
6.Ensure that the fuel does not leak from the fuel rail service valve. Install the protective cover onto the fuel rail service valve.
7.If the fuel pressure reading was below the specifications, test the system according to the following procedure:
A.Perform the fuel pressure release procedure.
B.Install a fuel gauge and fuel adapter 6631 or equivalent in the fuel supply line between the tank and the fuel filter.
C..Place the ignition key in the ON position.
8.If the pressure is at least 5 psi (1 kPa) or higher than the reading recorded, replace the fuel filter.
9.If no change is observed, gently squeeze the return hose. If the pressure increases, replace the pressure regulator. If the gauge reading does not change when the return hose is squeezed, the problem is either a plugged inlet strainer or defective fuel pump.
10.If the fuel pressure reading was above the specifications test the system according to the following procedure:
A.Perform the pressure release procedure.
B.Install fuel pressure gauge and adapter 6631 or equivalent in the fuel supply line between the fuel tank and the fuel filter.
C.Remove the fuel return line hose from the pump at the tank. Connect pressure test adapter 6668 or equivalent to the return line. Place the other end of adapter 6668 into an approved gasoline container. A minimum of 2 gallon tank should be sufficient. All return fuel will flow into the container.
D. Place the ignition key in the ON position.
11.If the pressure is now correct, replace the fuel pump.
12.If the pressure is still above specifications, remove the fuel return hose from the chassis fuel tubes (at the engine) and attach fuel pressure test adapter 6668 or equivalent to the return tube. Place the other end of the hose in the clean container, repeat the test. If the pressure is now correct, check for a restricted fuel return line. If there is no change observed, replace the fuel pressure regulator.