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Home >> Kia >> 2023 >> Niro Plug-In Hybrid EX >> Repair and Diagnosis >> Engine Performance >> Fuel Delivery >> Fuel Delivery System (PHEV) >> Fuel Pressure Test >> Fuel Pressure Test

Fuel Pressure Test

WARNING:
  • When working on the high voltage system, the work should be performed by technicians who have completed the relevant training. A lack of understanding of the high voltage system can lead to serious accidents due to electric shock or short circuit.
  • When working on the high voltage system or related components, be sure to observe and be aware of the "HIGH VOLTAGE SYSTEM GENERAL SAFETY INFORMATION AND CAUTION ". If not, it may cause serious accidents due to electric shock or short circuit.
  • When working on high voltage system, make sure to check the PERSONAL PROTECTIVE EQUIPMENT (PPE) and HIGH VOLTAGE SHUT-OFF PROCEDURES .
  1. Release the residual pressure in fuel line.

    (Refer to Fuel Delivery System -  "RELEASE RESIDUAL PRESSURE IN FUEL LINE ")

    NOTE: 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. Remove the air cleaner assembly.

      (Refer to Engine Mechanical System -  "AIR CLEANER ")

    2. Separate the fuel feed tube connector (A) after opening the clamp cover.
      G15787762Courtesy of KIA MOTORS AMERICA, INC.
      NOTE:
      • Cover the connection with a clean cloth since the residual fuel may be released after "RELEASE RESIDUAL PRESSURE IN FUEL LINE " procedures.
      • When separating the fuel supply tube, separate it after pressing the holder (A) firmly by using the clip remover.
        G15787763Courtesy of KIA MOTORS AMERICA, INC.
      • After separating the fuel feed tube, block the high pressure fuel pump/connection area to prevent contamination.
      G15787764Courtesy of KIA MOTORS AMERICA, INC.
    3. Install SST (09353 - 24100, 0K353 - D4100) for measuring the fuel pressure between the low pressure fuel feed tube and the high pressure fuel pump.
    G15787765Courtesy of KIA MOTORS AMERICA, INC.
  3. With the IG ON, check the fuel line and SST connections for the leaks.
  4. Measure fuel pressure.
    1. Start the engine and measure the fuel pressure at idle.

      Fuel pressure: 

      480 - 520 kPa (4.89 - 5.30 kgf/cm2 , 69.62 - 75.42 psi)

      NOTE: 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

      NOTE: If the gauge reading does not hold pressure, 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 IG OFF.
  5. Release the residual pressure in fuel line.

    (Refer to Fuel Delivery System -  "RELEASE RESIDUAL PRESSURE IN FUEL LINE ")

    NOTE: Cover the connection with a clean cloth since the residual fuel may be released after "Release Residual Pressure in Fuel Line" procedures.
  6. Finish test.
    1. Remove 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.
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