Transfer Fuel Pump -G6-, CHECKING, TDI VEHICLES

WARNING: This page is about a different variant/trim than selected.

Special tools and workshop equipment required

Diesel Pressure Tester Kit:VAS 6551 with Diesel Pressure Tester Kit - Hose 2:VAS 6551/2

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Diesel Pressure Tester Kit - Adapter Set:VAS 6551/5

Fig 1: Identifying Diesel Pressure Tester Kit - Adapter Set
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Diesel Pressure Tester Kit - Pressure Regulator Valve:VAS 6551/6

Fig 2: Identifying Pressure Regulator Valve
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Diesel Pressure Tester Kit - Hose Adapter Set:VAS 6551/7
Vehicle Diagnostic Tester
Fuel-Resistant Measuring Container

A - Checking fuel delivery rate

Fig 3: 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-.

-- Remove the engine cover. Refer to ENGINE COVER, REMOVING AND INSTALLING (2.0L) , ENGINE COVER (3.0L) .

WARNING:

The fuel system is under pressure.

Risk of injury from fuel spraying out.

Wear protective eyewear.
Wear safety gloves.
Reduce the pressure: place clean cloths around the connection point and carefully open the connection point.

2.0L TDI vehicles:

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-- Loosen the hose clamp -2- and remove the fuel supply hose from the fuel supply line to the high pressure pump.

-- Connect the Diesel Pressure Tester Kit - Adapter Set - Adapter 1:VAS 6551/5-1 to the fuel supply hose -1-, secure it with a hose clamp and attach the Diesel Pressure Tester Kit - Hose 2:VAS 6551/2 .

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-- Connect the Diesel Pressure Tester Kit - Hose 2:VAS 6551/2 to the Diesel Pressure Tester Kit:VAS 6551 .

-- Attach the Diesel Pressure Tester Kit - Pressure Regulator Valve:VAS 6551/6 and hold the hose in a fuel-resistant measuring container.

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

3.0L TDI vehicles:

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-- Disconnect the fuel supply hose -1- to the high pressure pump. Disconnect the connector couplings. Refer to CONNECTOR COUPLINGS, DISCONNECTING .

-- Connect the Diesel Pressure Tester Kit:VAS 6551 to the fuel supply hose using the Diesel Pressure Tester Kit - Hose Adapter:VAS 6551/7-2 .

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-- Attach the Diesel Pressure Tester Kit - Pressure Regulator Valve:VAS 6551/6 and hold the hose in a fuel-resistant measuring container.

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

Continuation for All Vehicles:

Fig 4: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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-- Switch on the Diesel Pressure Tester Kit:VAS 6551 -item 1- by pressing the On/Off button.

NOTE:

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:VAS 6551/6 as follows:

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

The levers point in the flow direction.

CAUTION:

Risk of fuel leaking.

The shut-off valve -C- must be closed.
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:

Drivetrain
Select the engine code and engine
0001 - OBD-capable systems
0001 - Engine Electronics
0001 - Engine electronics, functions
0001 - Fuel pump activation
Perform the test

-- Start the fuel pump and let it run for 15 seconds.

-- To generate the initial pressure in the fuel system, turn the adjusting screw -1- on the Diesel Pressure Tester Kit - Pressure Regulator Valve:VAS 6551/6 until the correct initial pressure value is reached.

Fig 5: Identifying Pressure Regulator Valve Adjusting Screw

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Specified value: 4.5 bar (65.27 psi) pressure.

NOTE:

If the 15 second start is not sufficient to adjust the initial pressure, repeat the procedure.

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

-- Empty the measuring container.

-- Start the fuel pump and let it run for 15 seconds.

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

4-cylinder specified value: minimum delivery rate 750 cm³ /15 s.
6-cylinder specified value: minimum delivery rate 1000 cm³ /15 s.

If the minimum delivery rate is attained:

Fuel supply line, fuel filter and fuel pump are OK.
However, there may be a malfunction in the fuel return. For fault finding, perform an "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.
The fuel filter is clogged.

NOTE:

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 6: 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:VAS 6551 -item 1- by pressing the On/Off button.

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

The lever points in the flow direction.

CAUTION:

Risk of fuel leaking.

The shut-off valves -B and C- must be closed.
The levers face perpendicular to the flow direction.

-- Start the fuel pump and let it run for 15 seconds.

-- Read the fuel pressure on the Diesel Pressure Tester Kit:VAS 6551 .

Specified value: 6.0 to 8.0 bar (87.02 to 116.03 psi).

If the specified value is obtained, even though the fuel delivery rate was not OK:

Fuel supply line is crushed.
The fuel filter is clogged.

If the specified value is not attained:

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

NOTE:

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.

Decrease the fuel pressure by opening the shut-off valves -B and C- and allowing the fuel drain into the measuring container before disassembling the measuring system.

Fig 7: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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-- Disassemble the Diesel Pressure Tester Kit - Pressure Regulator Valve:VAS 6551/6 and remove it with the measuring container.

Fuel delivery rate and pressure test in the fuel supply is OK.
Diesel Pressure Tester Kit - Adapter Set - Adapter 1:VAS 6551/5-1 and Diesel Pressure Tester Kit - Hose 2:VAS 6551/2 connected to the fuel supply hose and to the Diesel Pressure Tester Kit:VAS 6551 .
Vehicle Diagnostic Tester is connected.

-- Connect the Diesel Pressure Tester Kit - Adapter Set - Connection Hose 2:VAS 6551/5-2 to the fuel supply line for the high pressure pump and to the Diesel Pressure Tester Kit:VAS 6551 .

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NOTE:

The Diesel Pressure Tester Kit:VAS 6551 is switched on in the fuel supply line.

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-- Disassemble the Diesel Pressure Tester Kit - Pressure Regulator Valve:VAS 6551/6 and remove it with the measuring container.

Fuel delivery rate and pressure test in the fuel supply is OK.
Diesel Pressure Tester Kit - Hose Adapter:VAS 6551/7-2 is connected to the fuel supply hose and to the Diesel Pressure Tester Kit:VAS 6551 .
Vehicle Diagnostic Tester is connected.

-- Connect the Diesel Pressure Tester Kit - Hose Adapter:VAS 6551/7-1 to the fuel supply hose for the high pressure pump and to the Diesel Pressure Tester Kit:VAS 6551 .

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NOTE:

The Diesel Pressure Tester Kit:VAS 6551 is switched on in the fuel supply line.

Continuation for All Vehicles:

Fig 8: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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-- Switch on the Diesel Pressure Tester Kit:VAS 6551 -item 1- by pressing the On/Off button.

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

The levers point in the flow direction.

CAUTION:

Risk of fuel leaking.

The shut-off valve -C- must be closed.
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:

Drivetrain
Select the engine code and engine
0001 - OBD-capable systems
0001 - Engine Electronics
0001 - Engine electronics, functions
0001 - Fuel pump activation
Perform the test

-- Start the fuel pump and let it run for 15 seconds.

-- Read the fuel pressure on the Diesel Pressure Tester Kit:VAS 6551 .

Specified value: 3.8 to 5.8 bar (55.11 to 84.12 psi).

If the specified value is not reached, although the fuel delivery rate was OK:

The high pressure pump overflow valve is not OK

If specified value is not reached:

The fuel return line is blocked or kinked.

Assembling

Assemble in the reverse order of removal.

The ignition must be off.

NOTE:

Decrease the fuel pressure by opening the shut-off valves -B and C- and allowing the fuel drain into the measuring container before removing the pressure tester -1-.

Fig 9: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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-- Remove the Diesel Pressure Tester Kit:VAS 6551 with the connecting lines.

-- Secure the fuel supply line with a hose clamp and then pull on it to make sure the fuel supply line is secured properly.

-- Install the engine cover. Refer to ENGINE COVER, REMOVING AND INSTALLING (2.0L) , ENGINE COVER (3.0L) .