The fuel pump regulates the flow of fuel from the gas tank to the fuel intake system of your engine. Without the pump, the engine is starved of fuel and dies. A faulty fuel pump on an Infiniti Q45 can lead to damage to fuel sensors and lead to repairs that will cost far more than what it does to have the fuel pump replaced. Unlike a lot of other vehicles, the fuel pump on a 1993 Infiniti Q45 is just above the fuel tank. This requires removing the back seat and replacing it while standing in the trunk.
M/F Park the Infiniti on a level surface, and use the parking brake to keep it in place.
M/F Remove the fuel pump fuse in the fuse box, and start the vehicle; this will pull the gas still in the pump and the fuel lines into the engine of the vehicle while not allowing new fuel to be pumped through the lines.
M/F Remove the gas cap on the car. When you are ready to remove the fuel pump, there might be a rapid release of remaining fuel because of vapor pressure. Removing the gas cap reduces that pressure and minimizes the spillage.
M/F Disconnect the negative battery cable from the negative terminal on the battery. When working with gas and gas fumes, one static electric spark could cause serious damage to the car and injury to you.
M/F Remove the rear seats from the Infiniti. If these are bench seats, you will have to unbolt the seat from the bottom inside frame. Use a ratchet or socket wrench to remove these bolts. If you have bucket seats in the rear, the procedure is the same, you will just have to remove each individually. You will have to move the driver and passenger seats to tilt forward so you can remove the rear seats.
M/F Open the trunk lid, and remove the inside lining shield. There will be seven black Phillips anchor clips holding the bulkhead to the steel frame of the Infiniti. Remove the passenger-side bulkhead between the trunk and the rear fender. There will be five black Phillips anchor clips that can be removed with a screw driver. You will have to remove the spare tire and all the items in the trunk. Locate the fuel pump, which is on the top of the fuel tank just under the center of the trunk.
M/F Disconnect the blue fuel pump connector from the fuel pump harness. Set some towels down in the back seat area to catch leftover gas spillage. Use a 19 mm open-end wrench to remove the two tubing nuts that secure the metal fuel pump outlets and hoses to the top of the fuel pump assembly.
M/F Remove the fuel tank assembly cover plate. There will be six 8 mm bolts that can be removed by an 8 mm box wrench. Pull the fuel pump off the tank gently, using caution not to allow the large black "O" ring to fall into the gas tank. Many new fuel pumps will come with this "O" ring, as Nissan recommends changing it at the same time you replace the pump.
M/F Remove the braces from the old pump -- these will be made of black rubber -- and then remove the fuel pump from the assembly completely. Install the new pump by following the removal directions in reverse. Reconnect the pump to the fuel tank, reinstall the rear seats, the trunk bulkheads and the gas cap. Reconnect the negative battery cable and the fuel pump fuse, and start your Infiniti.
M/F Do not smoke or be around open flames in attempting this job. Discard the towel you used if gas spilled on it. You don't want to risk gas surviving the washer and igniting in the dryer.