Kia Optima: Engine Control / Fuel System / Fuel Delivery System

Release the residual pressure in fuel line.

(Refer to Fuel Delivery System - "Release Residual Pressure in Fuel Line")

When removing the fuel pump relay, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the KDS after completion of “Release Residual Pressure in Fuel Line” work.

Install the Special Service Tool (SST).

(1)

Separate the fuel feed tube quick-connector (A). • Open the clamp cover before disconnecting the quick-connector. • Separate the quick-connector after pressing the clip (A) certainly using the clip removing tool. • Damaged clip can result in fuel line leakage due to bad connection. • There may be some residual pressure even after completing “Release Residual Pressure in Fuel Line”, so cover the hose connection with a shop towel to prevent residual fuel from spilling out before disconnecting any fuel connection.

Inspect fuel leakage on connections among the fuel feed tube, the delivery pipe, and the SST components with IG ON.

Measure Fuel Pressure.

(1)

Start the engine and measure the fuel pressure at idle. Fuel Pressure: 330 - 370 kPa (3.36 - 3.77 kgf/cm², 47.8 - 53.6 psi) If the fuel pressure differs from the standard value, repair or replace the related part (Refer to the table below). Fuel Pressure Cause Related Part Too Low Fuel filter clogged Fuel Filter Fuel leakage Fuel Pressure Regulator Too High Fuel pressure regulator valve stuck Fuel Pressure Regulator

(2)

Stop the engine, and then check for the change in the fuel pressure gauge reading. Standard Value: The gauge reading should hold for about 5 minutes after the engine stops If the gauge reading should not be held, repair or replace the related part (Refer to the table below). Fuel Pressure (After Engine Stops) Cause Related Part Fuel Pressure Drops Slowly Leakage on injector Injector Fuel Pressure Drops Immediately Check valve of fuel pump stuck open Fuel Pump

Release the residual pressure in fuel line.

(Refer to Fuel Delivery System - "Release Residual Pressure in Fuel Line")

When removing the fuel pump relay, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the KDS after completion of “Release Residual Pressure in Fuel Line” work.

Remove the SSTs from the fuel feed tube and the delivery pipe.

Install the fuel feed tube from the delivery pipe.

There may be some residual pressure even after “Release Residual Pressure in Fuel Line” work, so cover the hose connection with a shop towel to prevent residual fuel from spilling out before disconnecting any fuel connection.

After disconnecting the negative battery terminal, remove the fuel pump fuse (A).

Connect the negative battery terminal.

After starting the engine and let idle, turn the ignition switch OFF after the engine has stopped on its own.

Install the fuel pump after disconnecting the battery negative (-) terminal, install the fuel pump fuse.

Delete the Diagnostic Trouble Code (DTC) related the fuel pump fuse with the KDS.