Hyundai Sonata: Repair procedures - Revised - Fuel Delivery System - Engine Control/Fuel SystemHyundai Sonata: Repair procedures - Revised

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: 445 ~ 455 kPa (4.5 ~ 4.6 kgf/cm², 64.5 ~ 66.0 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.

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: 480 ~ 520 kPa (4.9 ~ 5.3 kgf/cm², 69.6 ~ 75.4 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.

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 injury may be caused by the release of highly pressurized fuel. Release the residual pressure in the high pressure fuel line by referring to the "Residual fuel pressure release procedure" below before removing any high pressure fuel system components..
Wear safety glasses and fuel resistant gloves.
1.
Turn the ignition off and disconnect the battery negative cable.
2.
Remove the fuel pump relay (A).
3.
Disconnect the electrical connector from the high pressure fuel pump.
4.
Reconnect the battery negative cable.
5.
Run the engine for about 20 seconds to lower the pressure in both the high or low pressurelines. The engine may shut off within the 20 second period. If not, turn the engine off.
6.
Proceed with the service or repair. Use rags to cover opening and catch spills when opening up the high pressure system.
7.
Reinstall / re-connect all components in reverse order of removal. Start engine and confirm proper operation, and make sure there are no fuel leaks.
8.
After completing, clear DTC(s) using GDS scan tool (the procedure described above will cause DTC to set).

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