Transfer Fuel Pump, Checking
Transfer Fuel Pump, Checking
--> [ Delivery Quantity, Checking ]
--> [ Voltage Supply, Checking ]
--> [ Current Draw, Checking ]
Special tools, testers and auxiliary items required
• Vehicle Diagnosis Tester for example Vehicle Diagnosis, Testing and Information System (VAS 5051 B)
• Test instrument adapter/DSO (5-pin) (VAS 5565)
• Current pick-up (V.A.G 1526 B/2)
• Hand-held multimeter (V.A.G 1526 D)
• Pressure gauge (VAS 6550)
• Measuring container (3 liter)
CAUTION!
• Observe safety precautions when working on fuel supply. Refer to --> [ Fuel Supply System, Safety Precautions ] .
• Observe rules for cleanliness. Refer to --> [ Clean Working Conditions ] .
Always follow these instructions before and during work.
Delivery Quantity, Checking
Test Conditions
• The battery voltage must be at least 12,0 V.
• The fuses must be OK.
• All electrical consumers such as, for example, lights and rear window defroster must be switched off.
Test Sequence
- Disconnect connector - 1 - from auxiliary fuel pump.
- Disconnect black fuel supply line - A - to fuel tank.
- Connect pressure gauge (VAS 6550) at the fuel supply line - A - to the fuel tank.
- Guide open end of the hose from pressure gauge (VAS 6550) into measuring container.
- Open shut-off valves in direction of flow before and after the manometer and close the lower shut-off valve.
- Connect vehicle diagnosis tester - 1 - as follows:
- Connect diagnostic cable - 2 - to DLC in driver footwell.
- Switch on ignition.
- Perform "Guided Function, Checking electrical fuel pumps".
• The fuel pump now runs for 60 seconds.
- By carefully closing the shut-off valve behind the manometer, adjust the pressure to 0.5 bar.
- Stop tester test sequence if necessary and empty the measuring container.
- Guide open end of the hose from pressure gauge (VAS 6550) back into measuring container.
- Start "Guided Function, Checking electrical fuel pumps" again.
• The fuel pump now runs for 60 seconds.
- Switch off ignition.
- Read the quantity of fuel in the measuring container.
Specified Values
• Min. 1950 ml/60 seconds
• Maximum 2750 ml/60 seconds
If the quantity of fuel delivered is less than the specified value:
- Check fuel pump voltage supply and current draw. Refer to --> [ Voltage Supply, Checking ] , and to --> [ Current Draw, Checking ].
Voltage Supply, Checking
Test Conditions
• The battery voltage must be at least 12.0 V.
• The fuses must be OK.
• All electrical consumers such as, for example, lights and rear window defroster must be switched off.
Test Sequence
- Remove seat bench.
- Unclip cover - 1 - for fuel delivery unit. Arrow - 2 - points in direction of travel.
- Switch on ignition.
• The transfer fuel pump must run audibly for approximately 2 seconds.
• The transfer fuel pump runs quietly.
- Switch off ignition.
If transfer fuel pump does not run:
- Remove connector - 1 - from the fuel filler unit flange.
- Connect test instrument adapter/DSO (5-pin) (VAS 5565) between connector and the flange.
- Connect multimeter (V.A.G 1526 D) to the test contacts - 1 - and - 5 - on the adapter.
- Connect vehicle diagnosis tester - 1 - as follows:
- Connect diagnostic cable - 2 - to DLC in driver footwell.
- Switch on ignition.
- Perform "Guided Function, Checking electrical fuel pumps" with the.
• The fuel pump now runs for 60 seconds.
- Read voltage value on the multimeter.
• Specified value: Approximately battery voltage
- Switch off ignition.
If there is no voltage:
- Check fuel pump relay activation and the wires for open circuit and short circuit with.
Voltage supply OK:
- Fuel delivery unit, removing, refer to --> [ Fuel Delivery Unit ]
- Check if the electrical wiring between the flange and fuel pump is connected and has continuity.
If no open circuits are found replace fuel delivery unit --> [ Fuel Delivery Unit ] .
Current Draw, Checking
Test Conditions
• The battery voltage must be at least 12.0 V.
• The fuses must be OK.
• All electrical consumers such as, for example, lights and rear window defroster must be switched off.
• The fuel temperature in the fuel tank is above 10 °C.
• The battery voltage and the temperature of the diesel fuel have a strong influence on the fuel pump current draw.
• For this reason, make sure the battery voltage is at least 12V and the fuel temperature in the fuel tank is above 10 °C when testing.
Test Sequence
- Remove seat bench.
- Unclip cover - 1 - for fuel delivery unit. Arrow - 2 - points in direction of travel.
- Remove connector - 1 - from fuel filler unit flange.
- Connect test instrument adapter/DSO (5-pin) (VAS 5565) between connector and the flange.
- Connect current pick-up (V.A.G 1526 B/2) - A - to the red wire with the word "current clamp " on the adapter.
• The multimeter (V.A.G 1715) current pick-up can also be connected to the red wire with the word "current clamp" on the adapter.
- Connect multimeter (V.A.G 1526 D) to the current pick-up.
- Disconnect connector - 1 - from the auxiliary fuel pump (in the right of the engine compartment.
- Connect vehicle diagnosis tester - 1 - as follows:
- Connect diagnostic cable - 2 - to DLC in driver footwell.
- Switch on ignition.
- Perform "Guided Function, Checking electrical fuel pumps" with the.
• The fuel pump now runs for 60 seconds.
- Read current draw on the multimeter.
Specified value:
• Min. 5.5 amps
• Max. 7.5 amps.
- Switch off ignition.
If current draw is below the specified value, replace fuel delivery unit. Refer to --> [ Fuel Delivery Unit ] .