Checking Regulation Of The Fuel Pressure

HINT: The method described below is used to check the control of the pressure in the fuel injection system by activating the quick test for the fuel pump (FP). If the pressure gauge for pressures up to 650 kPa is connected, the fuel pressure sensor can also be checked during this test. 

• Disconnect the manometer unless it is adapted for pressures higher than 650 kPa
• Run the engine to operating temperature. Allow the engine to idle.
• air conditioning (A/C) off
• Read off the fuel pressure and the fuel pressure desired value.
• Start the quick test when the engine is running at idling.

  During the course of the quick test, the control module will steer the pressure to different target values in different stages (400, 500, 600 and finally 700 kPa), after which the pressure will be decreased in stages to the same pressure. Each stage lasts for approximately 5 seconds.

  NOTE:

  Because the by-pass valve in the fuel pump (FP) will be open at approximately 650 kPa, the pressure will not go higher than this.

  HINT:  Fig 2  shows an example of normal regulation. 

  • The upper digital display and the graphic display (red font color) indicate the absolute fuel pressure, calculated from the fuel pressure sensor
  • The central digital display and the graphic display (blue font color) indicate the control module target value for the absolute fuel pressure
  • The lower digital display indicates the relative fuel pressure (white font color), calculated from the fuel pressure sensor and the atmospheric pressure sensor (= absolute pressure minus atmospheric pressure). If a manometer is connected during the test, it must indicate this pressure.

  Check that the value for absolute fuel pressure is the same as the target value for absolute fuel pressure. If the values are not the same, this indicates a fault in the pressure regulation. The values may differ during the quick test when the target value is changed. This is due to sluggishness in the fuel regulation and is normal. In some cases, it can take up to 5 seconds before the fuel pressure reaches the target value for the fuel pressure.

  Fig 1: Identifying VCT2000 Diagnostic Tool Symbol In VIDA

  Courtesy of VOLVO CARS OF NORTH AMERICA.
  Fig 2: Identifying Example Of Normal Regulation

  Courtesy of VOLVO CARS OF NORTH AMERICA.

Is the function OK? 

• YES 

  Refer to CHECKING COMPONENTS 

• NO 

  Refer to CHECKING COMPONENTS