Fuel Pressure Relief

Whenever you need to open the fuel system, whether for fuel filter replacement or intake manifold removal, it is necessary to depressurize the fuel system. Because the fuel system runs at approximately 43 PSI, and is designed to maintain pressure even when the car is off (going so far as to pre-pressurize for the next start upon shut-down), simply removing a fuel line will leave you with a giant mess and probably a burning eye.

Disable the Fuel Pump

Before you can relieve fuel pressure, you must first disable the fuel pump. There are a few different ways you can do this.

Consult

1. Using a consult connection, enter the active test or work-support mode.
2. Select "OFF" under Fuel Pump.
3. Click Start.
4. Skip below to "Fuel Pressure Relief."

Fusible Link

1. Locate the fusible link box near the battery.
   
2. Remove the cover.
3. Remove the right-most fusible link (labelled FUEL PUMP, of all things) by squeezing the springy-tab on it and pulling upwards.
4. Skip below to "Fuel Pressure Relief."

Fuel Pump Connection

1. Gain access to the fuel pump itself.
   • On a 2+0, this is done by removing the parcel tray directly behind the seats.
     1. Remove the two plastic covers on either side of the tray by pulling straight up from the inner-side.
     2. Remove the screws under the carpet.
     3. Remove the parcel tray.
        
        

        Image source: Aus300ZX.com
   • On a 2+2, this is done by removing the rear spare tire & cover.
     1. Remove the rear carpet.
     2. Remove the spare tire.
     3. Remove the 4 Philips-head screws securing the fuel pump cover to the unibody.
        
        

        Image source: Aus300zx.com
2. Disconnect the fuel pump.
   1. For a 2+0, this is the large 4-wire white connector on the left.
      
   2. For a 2+2, this is the single gray oval connector.
3. Skip down to "Fuel Pressure Relief."

Fuel Pump Relay

Despite this being arguably the most cumbersome and difficult method, it seems to be the most common.
Images from dr_rabias of 300ZXClub.

1. Remove the driver's side door sills (4 x philips head screws).
2. Remove the driver's side kick panel (the plastic panel that houses the dead pedal).
   
3. Remove the bolts (2 x 10mm) holding the fuel pump relay bracket to the body.
   
4. Disconnect the fuel pump relay (green connector).
   
5. Skip down to "Fuel Pressure Relief."

Fuel Pressure Relief

Now that the fuel pump has been disabled, it's time to kill the fuel pressure!

1. Pop the gas door and remove the gas cap. You can re-install it by a couple of turns to prevent anything from falling in, but in general you want it open--this prevents ambient heat from creating positive pressure in the fuel tank, which would cause fuel to continue to flow from the lines once removed.
2. Crank the engine over. The engine will likely start.
3. Wait for the engine to die (if it starts). Crank it over an additional 5-10 seconds.
4. Re-enable the fuel pump by performing the reversal of whatever method you used to disable it.
5.  ???
6. Profit.

Don't forget to reconnect the fuel pump and re-install the gas cap when you're all done!