Kia Optima: 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 high
pressure fuel pump.
|
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 high
pressure fuel pump (Refer to the figure below). 
|
|
| 3. |
Inspect fuel leakage on connections among the fuel
feed tube, the high pressure fuel pump, and the SST components with
IG ON. |
| 4. |
Measure Fuel Pressure.
| (1) |
Start the engine and measure the fuel pressure
at idle.
Fuel Pressure: 495 ~ 505 kPa (5.1 ~ 5.2 kgf/cm²,
71.8 ~ 73.2 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 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 high pressure fuel pump. |
| (2) |
Connect the fuel feed tube and the high pressure
fuel pump. |
|
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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Release Residual Pressure in Fuel Line