Transfer Fuel Pump -G6-, CHECKING

Special tools and workshop equipment required

Pressure Tester Kit: VAS6550 with Pressure Tester Kit - Hose 2: VAS6550/2
Pressure Regulator Valve: VAS6550/4
Vehicle Diagnostic Tester
Fuel-Resistant Measuring Container

A - Checking Fuel Delivery Rate

Fig 1: The 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-.

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WARNING:

Risk of injury due to the fuel being under high pressure.

To reduce the pressure in the fuel system, lay clean cloths around the connection point and carefully loosen the connection point.

-- Free up the fuel hose from the brackets -1 and 3- and disconnect the connector coupling -2-. Refer to CONNECTOR COUPLINGS, DISCONNECTING .

-- Connect the : VAS6550 to the fuel supply line with the : VAS6550/2 .

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-- Connect the : VAS6550/4 and hold the hose in a fuel-resistant measuring container.

-- Switch on the : VAS6550 -1- by pressing the On/Off button.

Fig 2: Identifying Shut-Off Valves A And B On Pressure Tester Kit

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NOTE:

To measure the fuel delivery rate, an initial pressure must be created in the fuel line which the fuel pump must work against during measurement. Set the initial pressure using the : VAS6550/4 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 and start OBD mode.

Drivetrain
Engine
01 - OBD-capable systems
01 - Engine electronics
Basic setting
Drain fuel tank

-- Start the basic setting without measured values: the fuel pump starts.

-- Turn the adjusting screw -1- on the : VAS6550/4 to create an initial pressure in the fuel system until the correct initial pressure value is reached.

Fig 3: Identifying Pressure Regulator Valve Adjusting Screw

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Specified value: 4.5 bar (65.27 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 800 cm³ /15 s.

If the Minimum Delivery Rate Is Attained:

The fuel delivery unit with the fuel filter, fuel pressure regulator and fuel supply line is OK.

If the Minimum Delivery Rate Is Not Obtained, It May Be Due to the Following Malfunctions:

Fuel delivery unit with integrated fuel filter is faulty.
Fuel pressure regulator in the fuel delivery unit is faulty.
Fuel supply line is crushed.

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 4: 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 : VAS6550 -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.

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

-- If the fuel flows without bubbles, close the shut-off valve -B- so that the fuel pressure increases.

The lever is perpendicular to the flow direction.

-- Read the fuel pressure on the : VAS6550 :

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

-- Press the Stop button.

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

Fuel filter in the fuel delivery unit is plugged of the fuel supply line is crushed.

If the specified value is not attained:

Fuel delivery unit or fuel pressure regulator in the fuel tank is faulty.

C - Checking Residual Pressure

-- Watch the pressure decrease on the : VAS6550 while checking the residual pressure and checking for leaks:

There still must be a pressure of at least 3 bar (43.51 psi) after 10 minutes.

If the residual pressure drops below 3 bar (43.51 psi):

Check the fuel lines and their connections for leaks.
The check valve in the fuel pump leaks: replace the fuel delivery unit. Refer to FUEL DELIVERY UNIT/FUEL LEVEL SENSOR, REMOVING AND INSTALLING .

Assembling

Assemble in the reverse order of removal. Note the following:

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

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-- Remove the : VAS6550 with the connecting lines.

-- Attach the fuel supply line so that it clicks into place.

-- Press on the fuel supply line again and pull it to make sure the connector coupling is engaged correctly.