Checking Regulation Of The Fuel Pressure

WARNING:

In this test, the pressure in the fuel injection system will reach approximately 650 kPa. Disconnect the pressure gauge, as it is not intended to be used at such high pressures.

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.

NOTE:

In this test, the complete flow capacity of the system is not tested.

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 regulates the pressure for different target values in different steps (530, 490, 450, 410, 440, 490, 530 kPa). Each step takes 10 seconds. The test usually starts with the pressure momentarily going up to 650 kPa.

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: The illustration to the left 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 lower digital display and the graphic display (yellow 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 should 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 CORPORATION

Fig 2: Identifying Upper Digital Display And Graphic Display (Red Font Color)
Courtesy of VOLVO CARS CORPORATION

Is the pressure regulation correct?

YES
Refer to CHECKING COMPONENTS
NO
Refer to CHECKING COMPONENTS