Kia Optima: Repair procedures - Fuel Delivery System - Engine Control/Fuel SystemKia Optima: Repair procedures

Fuel Pressure Test
1.
Release the residual pressure in fuel line (Refer to “Release Residual Pressure in Fuel Line” in this group).
   
   
When removing the fuel pump relay, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the GDS after completion of “Release Residual Pressure in Fuel Line” work.
2.
Install the Special Service Tool (SST).
(1)
Disconnect 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.
(2)
Install the special service tool for measuring the fuel pressure in between the fuel feed tube and the fuel delivery pipe (Refer to the figure below).


3.
Inspect fuel leakage on connections among the fuel feed tube, the delivery pipe, and the SST components with IG ON.
4.
Measure Fuel Pressure.
(1)
Start the engine and measure the fuel pressure at idle.

Fuel Pressure: 333 ~ 353 kPa
(3.4 ~ 3.6 kgf/cm?, 48.3 ~ 51.2 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

(3)
Turn the ignition switch OFF.
5.
Release the residual pressure in fuel line (Refer to “Release Residual Pressure in Fuel Line”).
   
   
When removing the fuel pump relay, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the GDS after completion of “Release Residual Pressure in Fuel Line” work.
6.
Test End
(1)
Remove the Special Service Tool (SST) from the fuel feed tube and the delivery pipe.
(2)
Connect the fuel feed tube and the delivery pipe.
Release Residual Pressure in Fuel Line
   
   
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.
1.
Turn the ignition switch OFF and disconnect the battery (-) terminal.
2.
Remove the fuel pump relay (A).


   
   
When removing the fuel pump relay, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the GDS after completion of “Release Residual Pressure in Fuel Line” work.
3.
Connect the battery (-) terminal.
4.
Start the engine and let idle, and then turn the ignition switch OFF after the engine has stopped on its own.
5.
Disconnect the battery (-) terminal, and then install the fuel pump relay (A).
6.
Connect the battery (-) terminal.
7.
Delete the Diagnostic Trouble Code (DTC) related the fuel pump relay with the GDS.
Components and Components Location
Components Location 1. Fuel Tank2. Fuel Pump3. Fuel Filter4. Fuel Pressure Regulator5. Canister6. Auxiliary Canister7. Fuel Tank Air Filter8. Fuel Tank Band9. Fuel Filler Hose10. Natural Va ...

Fuel Tank Repair procedures
Removal 1. Release the residual pressure in fuel line (Refer to “Release Residual Pressure in Fuel Line”). 2. Lift the vehicle. 3. Remove the front side cover (A) and rear side cover ( ...

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Release Residual Pressure in Fuel Line
Whenever the high pressure fuel pump, fuel pipe, delivery pipe, or injector is removed immediately after shutting off the engine, an ...

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