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

Kia Optima DL3 2019-2020 Service and Repair Manual / Engine Control / Fuel System / Fuel Delivery System

Fuel pressure test
Fuel Pressure Test
1.

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.

2.

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.

(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:

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

(3)

Turn the ignition switch OFF.

5.

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.

6.

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

7.

Install the fuel feed tube from the delivery pipe.

Release residual pressure in fuel line
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.

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

2.

Connect the negative battery terminal.

3.

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

4.

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

5.

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

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