Quick Test of the Fuel Pump (FP)
Testing the fuel pump (FP)
Checking the diagnostic trouble codes (DTCs)
Note! When testing the fuel pump (FP), diagnostic trouble codes (DTCs) for the atmospheric pressure sensor or fuel pressure sensor must not be stored in the engine control module (ECM). Check that none of these diagnostic trouble codes (DTCs) are stored.
- Ignition on.
Read off diagnostic trouble codes (DTCs).
If any of these 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 as necessary
No - Checking the fuel pressure sensor
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Checking the fuel pressure sensor
Hint: The function of the fuel pressure sensor must be checked first. This can be done by comparing the signal from the fuel pressure sensor (read off using VIDA) with the actual fuel pressure (read using 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 injection system can reach approximately 650 kPa when this diagnostic trouble code (DTC) is stored. 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
No - Remedy as necessary
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Checking regulation of the fuel pressure
Warning! The pressure in the fuel system can reach approximately 650 kPa. Disconnect the pressure gauge; it is not intended for use at such high pressures.
Hint: The method checks the pressure in the fuel system by reading out the fuel pressure and the fuel pump (FP) work load. 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 pump (FP) work load.
- The upper digital display and the graphic display (red font color) indicate the absolute fuel pressure, calculated from the fuel pressure sensor
- The center digital display and the graphic display (blue font color) indicate the relevant work load for the fuel pump (FP) in order to maintain the present fuel pressure. (Normal value 50 % ±10 %.)
- 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 the fuel pressure value together with the value for the fuel pump (FP) work load. The requested pressure is 380 kPa at idling speed. A (relative) fuel pressure lower than 380 kPa together with a high fuel pump (FP) work load indicates a fault in pressure regulation.
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