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Home >> Kia >> 2005 >> Optima EX, 2.7 8 >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Engine Control System/Fuel System - 2.7L >> Fuel Delivery System >> Fuel Pressure Test
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Fuel Pressure Test

  1. Reduce the internal pressure of the fuel pipes and hoses by the following procedures.
    • Disconnect the fuel pump harness connector after removing the rear seat cushion.
    • Start the engine and after it stalls, turn the ignition switch to the OFF position.
    • Disconnect the battery negative (-) terminal.
    • Connect the fuel pump harness connector.
  2. Remove the bolt connecting the fuel line to the fuel filter.
    WARNING: Cover the hose connection with a shop towel to prevent splashing of fuel caused by fuel residual pressure in the fuel line.
  3. Using the fuel pressure gauge adapter, install the fuel-pressure gauge to the fuel filter. Tighten the bolt to the specified torque.

    Fuel pressure gauge to fuel filter: 25-35 Nm (250-350 kg.cm, 18-26 lb. ft)

    Fig 1: Installing Fuel Pressure Gauge Adapter & Fuel Pressure Gauge
    G00328600Courtesy of KIA MOTORS AMERICA, INC.
  4. Connect the battery's negative (-) terminal.
  5. Apply battery voltage to the terminal for the pump drive and activate the fuel pump: then, with fuel pressure applied, check that there is no fuel leakage from the pressure gauge or connection part.
  6. Start and run the engine at curb idle speed.
  7. Disconnect the vacuum hose from the pressure regulator, and plug the hose end. Measure the fuel pressure at idle.

    Standard value: 320-340 kPa (3.26-3.47 kg/cm2 , 46-49 psi)

    Fig 2: Disconnecting Vacuum Hose From Pressure Regulator
    G00328601Courtesy of KIA MOTORS AMERICA, INC.
  8. Measure the fuel pressure when the vacuum hose is connected to the pressure regulator.

    Standard value: Approx. 255 kPa (2.57 kg/cm2 , 37 psi)

    Fig 3: Checking Fuel Pressure
    G00328602Courtesy of KIA MOTORS AMERICA, INC.
  9. If the results of the measurements made in steps  7 and  8 are not within the standard value, use the table below to determine the probable cause, and make the necessary repairs.
    Fig 4: Fuel Pressure Symptom Chart (1 Of 2)
    G00328603Courtesy of KIA MOTORS AMERICA, INC.
  10. Stop the engine and check for a change in the fuel pressure gauge reading, which should hold for approximately 5 minutes. If the gauge indication drops, observe the rate of drop. Determine and remove the causes according to the following illustration.
    Fig 5: Fuel Pressure Symptom Chart (2 Of 2)
    G00328604Courtesy of KIA MOTORS AMERICA, INC.
  11. Reduce the pressure in the fuel line.
  12. Disconnect the hose and the gauge.
    WARNING: Cover the hose connection with a shop towel to prevent splashing of fuel caused by fuel residual pressure in the fuel line.
  13. Replace the O-ring of the end of the hose.
  14. Connect the fuel hose to the delivery pipe and tighten with the specified.
  15. Check for fuel leakage.
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