The 2004 Kia Optima fuel pump is part of a complete, in-tank, fuel management module. The fuel filter, fuel pressure regulator, fuel pump, fuel level sender that is part of the gas gauge and emissions control valve are all part of the fully integrated unit. If one failed component fails, other than the fuel filter, the entire assembly must be replaced. Although the package is compact and easy to replace, it is pricey; make sure the pump is defective by testing for positive voltage and a good ground at the pump connector.
Raise the trunk lid and access the fuel tank service cover in the upper right-hand side of the trunk ledge. Remove the cover and unplug the electrical connector that powers the fuel pump. Start the car and let it run until the engine dies. This will remove the high-pressure fuel that is in the line so fuel will not spray when the line is disconnected. Test for voltage by probing the positive and negative fuel pump wires with a test-light. Make sure there is a voltage signal to the pump. If there is, the pump is defective. Turn the key off when the car stalls and replace the pump.
Disconnect the fuel feed line with the quick disconnect feature that is part of the fuel line fitting. Squeeze the two tangs of the connector and pull the hose off. Remove the fuel vapor hose that goes to the vapor canister by loosening the clamp and pulling the hose off the vapor port. Remove the retainer ring that holds the pump assembly in place using a small shop hammer and screwdriver. Lightly tap the screwdriver against the indents on the retaining ring until it unscrews. (The ring looks like a large lid that screws to a jar.) Completely loosen the ring and remove the pump module by lifting it up and out.
Install a new pump module into the opening. The new module will come complete, including a new fuel filter. No parts will need to be transferred from the old pump module. Push the new module into the fuel tank and tighten the retaining ring into place. Snap the fuel feed line into place, making sure there is a distinctive snap as the line locks in. Install the vapor line and tighten the hose clamp. Do not leave this line off or fuel vapors will enter the car. Plug the wiring harness in, and replace the pump cover. Start the car.
