Changing a fuel pump on a Honda Civic is not a particularly difficult repair, but it could take you a bit of time. The fuel pump is located in the fuel tank so, in order to do this repair you will have to drop the fuel tank to access the pump. Before you get to that, however, there is some testing that should be done to make sure the pump needs to be replaced.
The symptoms of a fuel system problem are lack of power when you press the throttle pedal or your vehicle just won't start. Or, you might be driving along just fine and your car sputters and dies. There are a number of things that can go wrong in the fuel system so proper troubleshooting and diagnostics are essential.
Before you begin working on any fuel system parts you want to make sure your engine is cool. If you spill gasoline on hot engine parts you can end up with a serious fire hazard. You'll also want to be certain that you have some clean rags and a container to catch gasoline while you're disconnecting lines and testing operation.
To complete this task you will need a set of metric combination wrenches. A pressure gauge would also be recommended. If you don't own a pressure gauge there is a good chance you could borrow one from your local auto parts store by leaving a deposit for its return. In order to test the electrical system leading to the fuel pump you will also want an electrical meter capable of measuring resistance and voltage. You'll also need to have a container big enough to hold whatever fuel is in the tank, as you'll need to drain and remove the fuel tank to complete this repair. You'll also need a pair of jack stands and a jack.
You should first see if the pump is operating at all. Under the hood you will find the fuel filter attached to the firewall on the passenger side. To avoid the hazard of a spark igniting any spilled fuel, disconnect the negative battery cable before working on the fuel lines. Carefully remove the fuel line from the inlet side of the fuel filter. If the fuel pump is working this could be under pressure so you should have a rag around the fuel line to catch any spilled fuel. Using a 12mm open-end wrench, loosen the inlet line one turn and allow any pressure to leak off and be caught by the rag. When any pressure in the line is released, go ahead and completely loosen the bolt and disconnect the line.
Once the fuel line is disconnected and you've made sure that any spilled fuel has been cleaned up, put the end of the fuel line in a container. Reconnect the negative battery cable. Hopefully you have someone who can help you at this point but if you have a large enough container it's not absolutely essential. You just don't want to have any spilled fuel to create a hazard.
Turn on the ignition key and observe to see if any fuel is flowing into your container. You only need to check this for a few seconds so once you've determined whether there's fuel, turn off the ignition. If there is no fuel flow at all it's time to move on to the next step of troubleshooting. If you do have fuel coming out that line you next need to check the fuel pressure. Attach the pressure gauge to the end of the fuel line, turn the ignition back on and check the pressure. The pressure reading should be around 30psi. If there is fuel flowing but it is significantly below 30psi, it's quite certain that you will need to replace the fuel pump. If the fuel pressure is correct then it is most likely the problem is your fuel filter and you won't need a new fuel pump.
If there is no fuel at all coming out of the fuel line then you will need to do some additional troubleshooting. Since you need to have the pressure out of the fuel line to replace the pump, go ahead and leave this disconnected for now.
On the 1990 Civic there should be an access panel to the fuel pump connections under the rear seat on a hatchback or in the trunk on a sedan. You can't get to the fuel pump to replace it from here but you can perform the next step in your troubleshooting. Identify the wire leading to the fuel pump on the top of the fuel tank. With your meter connect the red probe to that wire and the black probe to a bare metal spot anywhere on the car. Turn on the ignition and see if there is a voltage reading of around 12 volts at that wire. If the voltage doesn't read 12volts or more the problem is either in the wiring, the fuel pump relay or a blown fuse, and you may not need to replace your fuel pump.
Fuse number 23, a 15 amp blade fuse, in the fuse box under the dash is for the fuel pump. Pull that fuse and inspect it to see if it's blown. If its, replace it and see if the fuel pump comes on when you turn on the ignition. If the fuse is good, or the fuel pump still doesn't work, the problem might be the relay. The relay is located under the steering wheel on the far right, near the fuse box. This relay isn't cheap so you should test the relay before replacing it. Looking at the blade connections on the relay with the tab up, the connections are numbered; 1 lower right, 2 upper right, 3 lower next to 1, and so on to 7 lower left and 8 upper left. Using some pieces of wire, preferably with alligator clips on each end, connect number 1 to the positive terminal on the battery and number 2 to the negative terminal on the batter. Check for resistance across number 5 and number 7 with your meter. If the resistance is high the relay is bad. Replace the relay and check again to see if the fuel pump works. If it still doesn't work, check the voltage to the pump again. If you don't have voltage, you most likely have a wiring problem between the relay and the fuel pump. If you do have voltage there, it's time to replace the fuel pump.
To replace the fuel pump you need to remove the fuel tank. Ideally this problem will happen when there's little to no fuel in the tank. But, of course, you can't plan for a problem like this so you'll have to work with what you have.
This would be a good time to remove the negative battery cable. Once again we'll be working with fuel around electrical connections so a stray spark could be dangerous.
From the access panel under the rear seat or in the trunk disconnect the wire leading to the fuel pump. Also disconnect the fuel line and the return line.
To prepare for removal of the fuel tank lift the car and put the jackstands under it to hold it securely. Never work under a vehicle supported by a jack alone. Remove the drain bolt and drain the fuel into the tank into an approved container. Place a jack or other support under the fuel tank and remove the nuts holding the tank strap in place. Allow the strap to fall free and carefully lower the tank. The tank may need to be pried loose from the undercoating as it may have become stuck over time.
When the tank is down, you can readily get to the fuel pump to replace it. Remove the six nuts holding the pump in place and carefully lift the pump out of the tank. Be certain to observe the direction the pump is installed. To replace the pump just put the new one into the tank in the same orientation as the old pump came out. Reinstall the tank in the reverse order it was removed using a new washer for the drain plug. Reconnect your hoses and wires from the access panel inside the car and reconnect the fuel line at the fuel filter. Hook the negative battery cable back up and if everything has gone right your new fuel pump will work perfectly and you're ready to drive away after you clean up your mess.
Replacing an in-tank fuel pump is not necessarily an easy task, but it's not really easy for the professional mechanics, either. And they will charge for their labor accordingly. If you follow the troubleshooting through to the end, however, you may find the problem isn't the fuel pump after all. And, if it is, you can save considerably from paying someone else to do this.