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

Fuel Pressure Test (Low pressure system)
1.
Release the residual pressure in fuel line.
(Refer to the Fuel Delivery System - Repair Procedures - "Release Residual Pressure in Fuel Line").
   
When removing the fuel pump fuse, 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 low pressure fuel feed tube from the low pressure inlet of 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 low fuel feed tube and the low pressure inlet of high pressure fuel pump (Refer to the figure below).

3.
Inspect fuel leakage on connections among the low fuel feed tube, the low pressure inlet of 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 ~ 500 kPa (4.9 ~ 5.1 kgf/cm?, 69.7 ~ 72.5 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 the Fuel Delivery System - Repair Procedures - "Release Residual Pressure in Fuel Line").
   
When removing the fuel pump fuse, 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 low pressure fuel feed tube and the low pressure inlet of high pressure fuel pump.
(2)
Connect the low pressure fuel feed tube and the low pressure inlet of 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 fuse (A).

3.
Reconnect the battery negative cable.
4.
Run the engine for about 1 minutes to lower the pressure in the low pressure line.
5.
Turn the engine off.
6.
Disconnect the low pressure fuel line quick connector at the High Pressure Pump. Use rags to cover opening and catch spills while removing the fuel line.
7.
Start the engine and let it idle until the engine stops. At this point the pressure should be under 30 psi.
8.
Proceed with the service or repair. Use rags to cover opening and catch spills when opening up the high pressure system.
9.
Reinstall / re-connect all components in reverse order of removal. Start engine and confirm proper operation, and make sure there are no fuel leaks.
10.
After completing, clear DTC(s) using GDS scan tool  (the procedure described above will cause DTC to set).
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