The Honda Civic's fuel pump is contained within a module that includes the fuel gauge sending unit. If the fuel pump needs replacing, you should replace the whole module. This module is stored near the bottom of the car near the rear end, but you do not need to remove the fuel tank to access it like with many other models.
Relieve the pressure in the fuel system by removing the PGM-FI relay Number 2. You need to remove the glove box to reach it, and it's the PGM-FI relay with the yellow/black, yellow/green, yellow/green and green/yellow wires. Start the engine and it should stop running immediately, then open the fuel cap on the side of the car.
Disconnect the battery's black negative cable. Please note that this causes the Powertrain Control Module to lose important information from its memory.
Remove the rear seat cushion from inside the car. Its retaining bolt is in between the cushion and the back support, requiring a wrench with an extended socket.
Open the access cover to the fuel pump/fuel gauge sending unit by removing the screws at the cover's four corners; these screws should require a Phillips screwdriver.
Unplug the electrical connector to the pump/sending unit by depressing the release tab and pulling the connector straight up. Disconnect the fuel supply line by pressing the two tabs on the quick-connect fitting. Loosen and remove the locknut for the unit using a special tool available at most auto parts stores.
Lift the fuel pump/fuel sending unit module out of the hole, tilting the unit so you won't damage the float arm or the float. Remove the rubber seal from the top of the unit and inspect it; replace it if it's cracked, deteriorated or otherwise damaged.
Install the rubber seal into the mounting hole by itself. Do not insert it with the new module, or it might get pinched or distorted.
Insert the replacement fuel pump/fuel gauge sending unit module into the hole, aligning the index mark on the top of the module between the two marks on the edge of the hole.
Re-connect the fuel supply line and electrical connector. Use a new O-ring within the quick-connect fitting for the supply line.
Close the access cover to the module with its screws and install the rear seat cushion.
Reconnect the negative battery cable.
Perform the idle learning procedure for the Powertrain Control Module. With all electrical components turned off, start the engine, bring it to 3000 RPM and let it run with the car in Park or Neutral for five minutes. If the radiator fan comes on at any time, stop the five minute count and continue it once the fan goes off.