Hyundai Elantra (CN7): Fuel Delivery System / Fuel pressure test

Hyundai Elantra (CN7) 2021-2025 Service 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 fuse, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the diagnostic tool 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 :
353 - 500 kPa (3.6 - 5.1 kgf/cm², 51.2 - 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 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 fuse, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the diagnostic tool 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.

    Components Location1. Fuel Tank 2. Fuel Pump3. Fuel Fiter4. Fuel Pressure Regulator5. Canister6. Fuel tank air filter7. Fuel pump plate cover8. Fuel filler hose9.

    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.

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