Transfer Fuel Pump -G6-, CHECKING, TDI VEHICLES: Notes

Special tools and workshop equipment required 

• Diesel Pressure Tester Kit: VAS6551  with Diesel Pressure Tester Kit - Hose 1: VAS6551/1  and Diesel Pressure Tester Kit - Hose 2: VAS6551/2 

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• Diesel Pressure Tester Kit - Pressure Regulator Valve: VAS6551/6 
  Fig 1: Identifying Pressure Regulator Valve

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• Vehicle Diagnostic Tester
• Fuel-Resistant Measuring Container

A - Checking Fuel Delivery Rate

Fig 2: Fuel Filler Cap

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-- Observe all test conditions. Refer to TEST CONDITIONS .

-- Open the fuel filler door.

-- Remove the fuel filler neck cap -arrow-.

-- Disconnect the fuel line -1-. Disconnect the connector couplings. Refer to CONNECTOR COUPLINGS, DISCONNECTING .

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-- Connect the Diesel Pressure Tester Kit: VAS6551  with the Diesel Pressure Tester Kit - Hose 2: VAS6551/2  to the fuel supply line.

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-- Attach the Diesel Pressure Tester Kit - Pressure Regulator Valve: VAS6551/6  .

-- Hold the hose in a fuel-resistant measuring container and secure the measuring container. A second technician may be required.

-- Switch on the Diesel Pressure Tester Kit: VAS6551  -1- by pressing the On/Off  button.

Fig 3: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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• To measure the fuel delivery rate, there must be an initial pressure inside the fuel supply line against which the fuel pump must work during the measuring. The initial pressure is adjusted using the Diesel Pressure Tester Kit - Pressure Regulator Valve: VAS6551/6  as follows:

-- Open the shut-off valves -A and B-.

• The levers point in the flow direction.

-- Close the shut-off valve -C-.

• The lever is perpendicular to the flow direction.

-- Connect the Vehicle Diagnostic Tester.

-- Switch the ignition on.

-- Select Diagnostic  and start.

-- Select the Select individual test  button and select the following tree structure consecutively:

• Diagnostic-capable systems
• 0001 - Engine Electronics
• 0001 - basic setting
• Transfer fuel pump test

-- Press Start  .

• The fuel pump starts.

-- To generate the initial pressure in the fuel system, turn the adjusting screw -1- on the Diesel Pressure Tester Kit - Pressure Regulator Valve: VAS6551/6  until the correct initial pressure value is reached.

Fig 4: Identifying Pressure Regulator Valve Adjusting Screw

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• Specified value: 4.0 bar (58.02 psi) pressure.

-- Do not turn the adjusting screw -1- any farther.

-- Press the Stop  button.

-- Empty the measuring container.

-- To measure, press the Start  button again and let the fuel pump run for 15 seconds.

-- After 15 seconds, press the Stop  button.

-- Check the fuel delivery rate in the measuring container.

• Specified value: minimum delivery rate 600 cm³ /15 s.

If the Minimum Delivery Rate is Attained:

• The fuel supply with the fuel pump are OK.
• However, there may be a malfunction in the fuel return. For fault finding, perform an "Entire System Pressure Test". Refer to C - Entire System Pressure Test .

If the Minimum Delivery Rate is Not Obtained, it May be Due to the Following Malfunctions:

• The fuel pump or fuel pressure regulator in the fuel tank is faulty.
• Fuel line is pinched.

To more accurately locate the malfunction, perform the "pressure test in the fuel supply line" described in the following.

B - Pressure Test in the Fuel Supply Line

Fig 5: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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• Set up the equipment as if measuring for the fuel delivery rate.
• Vehicle Diagnostic Tester is still connected.

-- Switch on the Diesel Pressure Tester Kit: VAS6551  -1- by pressing the On/Off  button.

-- Open the shut-off valve -A-.

• The lever points in the flow direction.

-- Close the shut-off valves -B and C-.

• The levers face perpendicular to the flow direction.

-- Press Start  on the Vehicle Diagnostic Tester display: the fuel pump starts running.

-- After 15 seconds, press the Stop  button.

-- Read the fuel pressure on the Diesel Pressure Tester Kit: VAS6551  .

• Specified value: minimum 4.0 bar (58.02 psi)

If the Specified Value is Obtained, Even Though the Fuel Delivery Rate was Not OK:

• Fuel supply line is crushed.

If the Specified Value is Not Attained:

• The fuel pump or fuel pressure regulator in the fuel tank is faulty.

• To also locate malfunctions in the fuel return line or the high pressure pump overflow valve, the "Entire system pressure test" must be performed as described in the following.
• Before replacing the measuring system, reduce the fuel pressure by opening the shut-off valves -B and C- and allowing the fuel to drain into the measuring container.
  Fig 6: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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