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High Pressure Fuel System Leak Test

WARNING: This page is about a different car, the 2024 Jeep Grand Wagoneer L and 2024 Jeep Grand Wagoneer. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

The high-pressure fuel system delivers fuel under extreme pressure from the injection pump to the fuel rail and injectors. This may be as high as 410 bar (5, 946 psi). Use extreme caution when inspecting for high-pressure fuel leaks. Fuel under this amount of pressure can penetrate skin causing personal injury or death. Inspect for high-pressure fuel leaks with a sheet of cardboard placed in the suspected area. Wear safety goggles and adequate protective clothing when servicing the fuel system.

  1. Install a diagnostic tool and monitor the Low Side Fuel Pressure and the Fuel Rail Pressure.
  2. Turn the ignition on and allow pressure to build without starting the engine.
  3. Turn the ignition off and observe the rate of fuel pressure decay on the diagnostic tool.
    NOTE:

    A faulty check valve in the fuel pump module can also cause fuel pressure decay. 

    • If the fuel pressures are similar (within 10 psi) and do not decay more than 10 psi in five minutes, it is safe to start the engine and check the high pressure fuel system.
    • If the pressure does not hold, inspect the fuel system, identify and correct the leak source.
  4. Start the engine and allow to run at idle for a short period.
  5. When fuel rail pressure stabilizes, turn off the engine.
  6. With the engine off and key on, observe the rate of fuel pressure decay on the diagnostic tool.
    • If the fuel pressure holds above 1000 psi for five minutes, there are no leaks present in the high pressure fuel system.
    • If the pressure does not hold, continue the diagnosis.
  7. Place a piece of cardboard (2) in the suspected area.
    GC0211749Courtesy of CHRYSLER GROUP, LLC
  8. Start the engine and allow to run at idle for a short period.
  9. Turn the engine off.
  10. Inspect the cardboard.
  11. Replace the high-pressure line if the connection (3) is leaking.
  12. If the fuel injector to fuel rail connection is leaking, replace the O-ring seal. Refer to INJECTOR(S), FUEL, REMOVAL AND INSTALLATION  .
  13. If the fuel rail pressure sensor is leaking, replace the sensor. Refer to FUEL RAIL PRESSURE SENSOR (FRPS) .
  14. Perform this procedure again and check for leaks.
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