Quick Test of the Fuel Pump (FP)
Quick test of the fuel pump (FP)
Checking the diagnostic trouble codes (DTCs)
Note! This method only applies to vehicles with demand controlled fuel pump (FP). For more information, see VIDA Design and Function.
Note! When activating a quick test of the fuel pump (FP), there must be no diagnostic trouble codes (DTCs) for atmospheric pressure or fuel pressure stored. Check that none of these diagnostic trouble codes (DTCs) are stored.
- Ignition on.
Read off diagnostic trouble codes (DTCs).
If any of the above diagnostic trouble codes (DTCs) are stored they must be remedied and erased first.
Are diagnostic trouble codes (DTCs) for the atmospheric pressure sensor or fuel pressure sensor stored?
Yes - Remedy diagnostic trouble codes (DTCs) as necessary
No - Checking the fuel pressure sensor
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Checking the fuel pressure sensor
Hint: Before starting the quick test, test the function of the fuel pressure sensor. This can be done by comparing the fuel pressure sensor signal (displayed in VIDA) with the actual fuel pressure (displayed on a manometer connected to the wiring for the fuel injection system). This method assumes that the manometer for measuring fuel pressure is correctly calibrated.
- Connect the manometer. See Fuel pressure gauge Fuel Pressure Gauge
Caution! The pressure in the fuel system can reach approximately 650 kPa. Use an adapted manometer.
- Run the engine to operating temperature. Allow the engine to idle
- Air conditioning (A/C) off.
Read off the relative fuel pressure.
The relative fuel pressure is calculated by VIDA from the fuel pressure sensor and the atmospheric pressure sensor signal (= absolute pressure minus atmospheric pressure).
Check that the value on the manometer and the value displayed in VIDA are the same. If the values are different, the circuit for the fuel pressure sensor is defective.
Is the function of the fuel pressure sensor OK?
Yes - Checking regulation of the fuel pressure (quick test)
No - Remedy as necessary
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Checking regulation of the fuel pressure (quick test)
Warning! In this test, the pressure in the fuel injection system will reach approximately 650 kPa. Disconnect the pressure gauge; it is not intended for use 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 the 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 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: The illustration to the left shows an example of normal regulation.
- The upper digital display and the graphic display indicate fuel pressure (absolute fuel pressure, calculated from the fuel pressure sensor).
- The center digital display and the graphic display indicate the fuel pressure reference value (target value for absolute fuel pressure).
- The lower digital display indicates relative fuel pressure (absolute fuel 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.
Hint: When idling with the engine at operating temperature, the fuel pressure must be approximately 400 kPa (4 bar).
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