Volkswagen 4-cyl. injection engine (1.8 and 2.0 l engine, chain drive). Manual (Edition 08.2018)

9.6.1

Checking function and voltage supply

• Battery voltage at least 12 V
• Fuse for fuel pump on fuse holder OK ⇒ Current flow diagrams,

Electrical fault finding and Fitting locations.

• Fuel pump control unit - J538- OK.
Test sequence

Note

♦

Function of fuel pump is checked using final control diagnosis.

♦

If the final control diagnosis is to be carried out several times

in succession, it may be necessary to start the engine briefly

before repeating the final control diagnosis.

– Connect vehicle diagnostic tester as follows:
– Push diagnosis cable connector onto diagnosis connection in

driver footwell.

– Switch ignition on.
– Press buttons on display one after the other for

Vehicle

self-diagnosis

Engine electronics

and

Final con-

trol diagnosis

– Press right arrow button

►

on display up to final control diag‐

nosis for fuel pump electronics.

The fuel pump must now run slowly up to maximum speed.

Note

The fuel pump runs very quietly.

– Switch off ignition.
If fuel pump does not run:
– Remove bench seat ⇒ General body repairs, interior; Rep. gr.

72 ; Rear seats; Removing and installing bench seat / individ‐

ual seats .

– Unclip cover -1- (which is on right side as seen in direction of

travel) at retaining tabs -arrows- using removal wedge - 3409- .

Note

For vehicles with auxiliary heater the metering pump - V54- con‐

nector must be separated additionally.

377

– First ensure that 5-pin wiring connection -1- is secure by pull‐

ing the connector without pressing the catch. If connector was

not inserted correctly, repeat functional check of fuel pump.

– Now pull off connectors -1-.
– Check the contacts on the connector and on the fuel delivery

unit for damage.

– Connect test instrument adapter/DSO (5-pin) - VAS 5565- to

connector and fuel delivery unit.

– Connect multimeter - V.A.G 1715- to contacts -1- and -5- of

adapters - VAS 5565- .

– Actuate fuel pump with final control diagnosis.
• The voltage must rise to about 9 V during the final control di‐

agnosis.

Voltage supply not OK:
– Locate and eliminate open circuit referring to current flow di‐

agram ⇒ Current flow diagrams, Electrical fault finding and

Fitting locations.

Voltage supply OK:
– Remove fuel delivery unit

⇒ page 366

– Check that electrical wires between flange and fuel pump are

connected.

If no open circuit can be found:
– Fuel pump defective, renew fuel delivery unit

⇒ page 366

9.6.2

Checking fuel pressure

Test conditions:
• Function of fuel pump has been checked

⇒ page 377

Test sequence

Note

♦

The fuel pressure must be checked by means of the final con‐

trol diagnosis. If the fuel pressure is measured at idling speed,

it may deviate from the specification.

♦

If the final control diagnosis is to be carried out several times

in succession, it may be necessary to start the engine briefly

before repeating the final control diagnosis.

WARNING

Fuel supply line is pressurised. Wear protective goggles and

protective clothing to avoid injury and contact with the skin.

Wrap a cloth around the connection before loosening hose

connections. Then release pressure by carefully pulling hose

off connection.

Rep. gr.20 - Fuel supply system

– Pull off supply line (metal coupling) -2- and catch escaping fuel

with a cloth.

– Connect pressure tester - VAS 6550- to fuel supply line with

adapter - VAS 6550/1- and -VAS 6550/2- .

– Make sure that drain tap is closed and cut-off taps are open.
– Actuate fuel pump with final control diagnosis to build up fuel

pressure.

– Read fuel pressure on pressure gauge.
• Specification: 4.0 to 7.0 bar
If fuel pressure is OK, check holding pressure

⇒ page 383

If specification is not obtained
– Renew left flange with pressure limiting valve, suction jet pump

and fuel filter.

Note

Pressure limiting valve and fuel filter are integrated into fuel gauge

sender 2 - G169- with suction-jet pump and cannot be renewed

individually.

– Repeat check.
If reading again does not match specification:
– Fuel pump defective, renew fuel delivery unit

⇒ page 366

379

9.6.3

Checking fuel pressure when the engine

is running and vehicle is in gear (engine

codes CCZA, CCZB, CCZC, CCZD)

Note

♦

If a complaint is made about the vehicle's performance, the

reason may be that the fuel pressure is too low. Faults in the

high-pressure section may also be caused by inadequate fuel

pressure in the low-pressure section. This check determines

the fuel pressure in the high-pressure and low-pressure sec‐

tions during a road test. Fuel pressure in the high-pressure

section is read from the engine control unit. The lowest fuel

pressure is measured by the pressure tester - VAS 6550- and

reported to the vehicle diagnosis and service information sys‐

tem - VAS 5052 B- .

♦

This test can be part of “Guided Fault Finding” if an entry has

been made in the event memory. However, it can also be star‐

ted in the vehicle diagnosis and service information system -

VAS 5052 B- by means of “Functions and component

selection”.

Special tools and workshop equipment required
♦ Pressure gauge - VAS 6550-
♦ Hose adapters - VAS 6550/1- and -VAS 6550/2-
♦ Vehicle diagnosis and service information system - VAS 5052

B-

♦ Connector cable - VAS 5051/66-
– Remove bench seat ⇒ General body repairs, interior; Rep. gr.

72 ; Rear seats; Removing and installing bench seat / individ‐

ual seats .

– Unclip cover -1- (which is on right side as seen in direction of

travel) at retaining tabs -arrows- using removal wedge - 3409- .

Note

For vehicles with auxiliary heater the metering pump - V54- con‐

nector must be separated additionally.

Rep. gr.20 - Fuel supply system

– First ensure that 5-pin wiring connection -1- is secure by pull‐

ing the connector without pressing the catch. The connector

can cause a fault if it has not been fitted correctly.

WARNING

The fuel line is under pressure.
Fuel poses danger of injury to eyes and skin.
Wear protective goggles and protective clothing to avoid injury

and contact with the skin. Wrap a cloth around the connection

before loosening hose connections. Then reduce pressure by

carefully opening the connection.

– Pull off supply line -2- and catch escaping fuel with a cloth.

381

– Connect pressure tester - VAS 6550- to fuel supply line with

adapter - VAS 6550/2- and -VAS 6550/1- .

– Fit connector cable - VAS 5051/66- to pressure tester - VAS

6550- and to vehicle diagnosis and service information system

- VAS 5052 B- .

– Make sure that drain tap is closed and cut-off taps are open.
– Switch on pressure tester - VAS 6550- .
If the fuel pressure test is carried out within “Guided Fault Find‐

ing”, follow the instructions of the diagnostic tester.
If the fuel pressure test is carried out without “Guided Fault Find‐

ing”, proceed as follows:
– Connect vehicle diagnosis and service information system -

VAS 5052 B- to vehicle.

– Select

Guided Fault Finding

in -VAS 5052 B- .

– Carry out identification of vehicle.
– Using the

GoTo

button, select the following menu options one

after the other:

♦

Function/component selection

♦

Drive

♦

Engine

♦

24 Mixture preparation/injection

♦

Mechanical components

♦

High-pressure pump

– Follow instructions on vehicle diagnosis and service informa‐

tion system - VAS 5052 B- .

WARNING

Test instruments and measuring equipment must always be

secured to the rear seat and operated by a second person from

this location.

Rep. gr.20 - Fuel supply system

9.6.4

Checking holding pressure

Prerequisites for check
• Fuel pressure OK and pressure tester - VAS 6550- connected.

Check fuel pressure

⇒ page 354

Test sequence
– Actuate fuel pump with final control diagnosis to build up fuel

pressure.

– Read fuel pressure on pressure gauge.
• Specification: 4.0 to 7.0 bar
– End self-diagnosis, and switch off ignition.
– Watch pressure drop on pressure gauge. Pressure must re‐

main above 3.0 bar for 10 minutes.

If the pressure drops further:
– Actuate fuel pump with final control diagnosis to build up fuel

pressure.

– After pressure has built up, close cut-off tap -B- of pressure

tester immediately. Lever is then at right angle to direction of

flow.

If the pressure drops again (leak on fuel tank side):
Leak must be sought on fuel tank side; proceed as follows:
– Check fuel line to flange for leaks.
If no fault is detected on »external« fuel lines, search for leak in

fuel tank. Proceed as follows:
– Open flanges on left and right. Ensure all hose connections

are fitted correctly and do not leak.

If no fault is found:
– First renew left flange with pressure limiting valve and fuel fil‐

ter. Repeat pressure retention test. If leak is still present, non-

return valve in fuel pump leaks, renew fuel delivery unit.

If the pressure does not drop now (leak on engine side):

Note

Search for leak on engine side. Repeat holding pressure test. This

time, close shut-off tap -A- to check whether leak actually is on

engine side.

– If there is a leak on the engine side, carry out external check

of the fuel pipes and high-pressure pump for leaks.

If no fault can be determined, check the injectors for leaks:
– Remove spark plugs. Open shut-off valves -A- and -B-. Ac‐

tuate fuel pump with final control diagnosis.

– Check through spark plug holes whether fuel has collected on

the piston crown due to a leaking injector.

383

9.6.5

Checking fuel delivery rate (engine co‐

des CAWA, CAWB, CCTA, CCTB)

Test conditions
• Voltage supply OK.
• When driving characteristic problems occur when the fuel tank

is a approx.

/4 filled, then check fuel delivery rates with ap‐

prox.

/4 filled tank or less.

– Remove bench seat ⇒ General body repairs, interior; Rep. gr.

72 ; Removing and installing bench seat .

– Remove right (in direction of travel) cover from fuel delivery

unit.

Note

For vehicles with auxiliary heater the metering pump - V54- con‐

nector must be separated additionally.

– First ensure that 5-pin wiring connection -1- is secure by pull‐

ing the connector without pressing the catch. The connector

can cause a fault if it has not been fitted correctly.

– Now pull off connectors -1-.
– Check the contacts on the connector and on the fuel delivery

unit for damage.

– Connect test instrument adapter/DSO (5-pin) - VAS 5565- to

connector and fuel delivery unit.

– Connect remote control - V.A.G 1348/3A- to test instrument

adapter/DSO (5-pin) - VAS 5565- and to battery positive (+).

Rep. gr.20 - Fuel supply system

– Pull off supply line (metal coupling) -2- and catch escaping fuel

with a cloth.

Note

Press in securing ring to release the fuel lines.

– Connect pressure tester - VAS 6550- to fuel supply line with

adapter - VAS 6550/2- . Hold adapter - VAS 6550/1- in a

measuring container.

– Make sure that drain tap is closed and cut-off taps are open.

WARNING

Danger of spray when shut-off tap is opened. Wear eye pro‐

tection and protective clothing to avoid injuries and skin con‐

tact. Hold container in front of open connection of pressure

tester.

– Operate remote control - V.A.G 1348/3A- . Then slowly close

shut-off tap -arrow- until a pressure of 4 bar is displayed on

pressure gauge. From this point on do not move position of

shut-off tap.

– Drain measuring container.

– The quantity delivered by the fuel pump depends on the bat‐

tery voltage. Therefore, connect multimeter - V.A.G 1715- to

wires -1- and -5- of adapter - VAS 5565- in addition.

– Operate remote control for 60 seconds while measuring volt‐

age at fuel pump.

385

– Compare quantity of fuel delivered with specification.
*) Minimum delivery rate cm³/60 s
**) Voltage at fuel pump with engine not running and pump run‐

ning.
Reading example:
During the test a voltage of 10.5 volts is measured. This equates

to a minimum delivery rate of approx. 1200 cm³/60 s
If specification is not obtained
– Check fuel lines for possible restrictions (kinks) or blockages.
If no fault is found:
– Remove cap from fuel filler neck and repeat check. If fuel de‐

livery rate is now reached, check fuel tank breather.

If reading again does not match specification:
– Open flanges on left and right. Ensure all hose connections

are fitted correctly and do not leak. Check sieve in fuel delivery

unit and fuel tank for coarse soiling.

If no fault is found:
– First renew left flange with pressure limiting valve and fuel fil‐

ter. Repeat delivery rate check. If fuel delivery is still insuffi‐

cient, fuel pump defective, renew fuel delivery unit.

If the fuel delivery rate has been attained but a fault is still sus‐

pected in the fuel supply system (e.g. intermittent failure of fuel

supply system):
– Measure current draw of fuel pump

⇒ page 388

9.6.6

Checking fuel delivery rate (engine co‐

des CCZA, CCZB, CCZC, CCZD)

Note

The fuel delivery rate must first be checked in the engine com‐

partment with the help of the function “Checking fuel delivery rate,

quick test”. If the minimum delivery rate is not achieved, a 2nd

measurement must be carried out at the flange of the fuel delivery

unit.

Checking fuel delivery rate in engine compartment:
– Connect vehicle diagnosis and service information system -

VAS 5052 B- to vehicle.

– Select

Guided Functions

in -VAS 5052 B- .

– Carry out identification of vehicle.
– Select

Engine

– Select

Checking fuel delivery rate, quick test

– Follow instructions on vehicle diagnosis and service informa‐

tion system - VAS 5052 B- .

Checking fuel delivery rate at flange:
• The guided function “Checking fuel delivery rate, quick test”

has been carried out ⇒ Vehicle diagnostic tester

Rep. gr.20 - Fuel supply system

• The remote control - V.A.G 1348/3A- and test instrument

adapter/DSO (5-pin) - VAS 5565- have been connected to the

fuel delivery unit.

• Battery charger connected
• Filling level in fuel tank above reserve
Test sequence

WARNING

The fuel line is under pressure.
Fuel poses danger of injury to eyes and skin.
Wear protective goggles and protective clothing to avoid injury

and contact with the skin. Wrap a cloth around the connection

before loosening hose connections. Then reduce pressure by

carefully opening the connection.

– Pull supply line -2- off right flange and catch escaping fuel with

a cloth.

– Connect pressure tester - VAS 6550- to flange with adapter -

VAS 6550/2- . Hold adapter - VAS 6550/1- in a measuring

container.

– Make sure that drain tap is closed and cut-off taps are open.
– Press the remote control - V.A.G 1348/3A- and slowly close

shut-off tap -arrow- until a pressure of 4 bar is displayed on

pressure gauge. From this point on do not move position of

shut-off tap.

– Drain measuring container.

– The quantity delivered by the fuel pump depends on the bat‐

tery voltage. Therefore, connect multimeter - V.A.G 1715- to

wires -1- and -5- of adapter - VAS 5565- in addition.

– Operate remote control for 60 seconds while measuring volt‐

age at fuel pump.

387

– Compare quantity of fuel delivered with specification.
*) Minimum delivery rate cm³/60 s
**) Voltage at fuel pump with engine not running and pump run‐

ning.
Reading example:
During the test a voltage of 10.5 volts is measured. This equates

livery rate is now reached, check fuel tank breather.

If reading again does not match specification:
– Open flanges on left and right. Ensure all hose connections

are fitted correctly and do not leak. Check sieve in fuel delivery

unit and fuel tank for coarse soiling.

If no fault is found:
– First renew left flange with pressure limiting valve and fuel fil‐

ter. Repeat delivery rate check. If fuel delivery is still insuffi‐

cient, fuel pump defective, renew fuel delivery unit.

If fuel delivery rate has been attained, but nevertheless you sus‐

pect a fuel supply system fault (e.g. intermittent failure of fuel

supply system): Check fuel pressure with the engine running

⇒ page 380

9.6.7

Checking current consumption

– Remove bench seat ⇒ General body repairs, interior; Rep. gr.

72 ; Removing and installing bench seat .

– Remove right (in direction of travel) cover from fuel delivery

unit.

– First ensure that 5-pin wiring connection -1- is secure by pull‐

ing the connector without pressing the catch. The connector

can cause a fault if it has not been fitted correctly.

– Now pull off connectors -1-.
– Check the contacts on the connector and on the fuel delivery

unit for damage.

Rep. gr.20 - Fuel supply system

– Connect test instrument adapter/DSO (5-pin) - VAS 5565- to

connector and fuel delivery unit.

– Connect pick-up clamp -A- to red terminal with lettering “pick-

up clamp” for test instrument adapter/DSO (5-pin) - VAS

5565- .

– Start engine and run at idling speed.
– Measure current draw of fuel pump.
• Specification: max. 16 amps

Note

♦

The starting current for the fuel pump can be briefly above

specifications when starting the engine.

♦

If the fuel system malfunction is intermittent, you can perform

the check during a road test, but a 2nd person is necessary.

If the current draw is exceeded:
– Fuel pump defective, renew fuel delivery unit

⇒ page 366

389

Electronic power control (EPC)

Assembly overview - accelerator module

⇒ page 390

Removing and installing accelerator module

⇒ page 390

10.1

Assembly overview - accelerator module

1 - Connector

❑ Black, 6-pin.

2 - Accelerator position sender

- G79- with accelerator posi‐

tion sender 2 - G185-

❑ Not adjustable.
❑ The accelerator position

sender passes the posi‐

tion of the accelerator

on to the engine control

unit.

❑ -A- openings for release

tool .

❑ Removing and installing

⇒ page 390

3 - 10 Nm
4 - Cover

10.2

Removing and installing accelerator

pedal module

Special tools and workshop equipment required

Rep. gr.20 - Fuel supply system

– Push release tool - T10238- (for right-hand drive vehicles re‐

lease tool - T10240- ) into intended holes as shown to stop

and remove accelerator module.

Note

In the Tiguan, raise the release tool slightly and then insert it at a

slight angle.

Installing

– Reconnect connector -1- to accelerator module -4-. Lock con‐

nector -arrow-.

– Press accelerator module onto securing pins -5-.
– Insert centring pin -6- into hole in underbody.
– Secure accelerator module with bolt -2- and install cap -3-.

– Install steering column trim.
Specified torque:

Component

Accelerator module to body

Rep. gr.20 - Fuel supply system

Activated charcoal filter system (Pas‐

sat, CC, Tiguan)

Assembly overview - activated charcoal filter system (engine co‐

des BZB, CAWA, CAWB, CGYA, CCZA, CCZB, CCZC, CCZD,

CDAA, CDAB)

⇒ page 393

Assembly overview - activated charcoal filter system (engine co‐

des CBFA, CCTA, CCTB)

⇒ page 394

Checking fuel tank breather (engine codes BZB, CAWA, CAWB,

CGYA, CCZA, CCZB, CCZC, CCZD, CDAA, CDAB)

⇒ page 396

Check fuel system for leaks CBFA, CCTA, CCTB

⇒ page 398

Note

♦

Hose connections are secured with either spring-type or

clamp-type clips.

♦

Spring-type clip pliers - VAS 6340- or space saving hose clip

pliers - VAS 6362- are recommended for installing and remov‐

ing spring-type clips.

The plug-in connectors for fuel, vacuum and breather lines are

colour coded. There is either a coloured dot on the plug-in con‐

nector or the release button is coloured.

Plug-in connector

Colour code on plug-in connec‐

tor

Fuel supply

black

Fuel return

blue

Breather

white, beige

Vacuum

green

11.1

Assembly overview - activated charcoal filter system (engine codes BZB,

CAWA, CAWB, CGYA, CCZA, CCZB, CCZC, CCZD, CDAA, CDAB)

393

1 - Activated charcoal filter

❑ Location: in rear right

wheel housing.

❑ To remove, unscrew se‐

curing bolts and pull ac‐

tivated charcoal filter

downwards out of re‐

tainer.

2 - Pressure retention valve

with connecting hose

❑ To remove, grasp se‐

curing ring (grey) and

pull off upwards.

❑ Ensure firm seating

3 - From fuel tank
4 - Breather line

❑ To activated charcoal fil‐

ter solenoid valve 1 -

N80-

⇒ Item 6 (page 394)

❑ Clipped onto fuel tank
❑ Ensure firm seating

5 - Breather line

❑ From activated charcoal

filter

⇒ Item 1 (page 394)

❑ Ensure firm seating

6 - Activated charcoal filter sol‐

enoid valve 1 - N80-

❑ Valve closed with igni‐

tion switched off

❑ When engine is warm,

valve will be activated

(pulsed) by engine control unit

7 - Connection hose

❑ To intake manifold
❑ Ensure firm seating

8 - 10 Nm

11.2

Assembly overview - activated charcoal

filter system (engine codes CBFA,

CCTA, CCTB)

Note

On some vehicles an additional filter is installed on the activated

charcoal filter system

Assembly overview - activated charcoal filter system

⇒ page 395

Assembly overview - activated charcoal filter system (vehicles

with additional filter)

⇒ page 396

Rep. gr.20 - Fuel supply system

11.2.1

Assembly overview - activated charcoal filter system

1 - Securing bolts
2 - Fuel system diagnostic

pump - V144-
3 - Vacuum line
4 - Clip
5 - Connection hose

❑ Activated charcoal fil‐

ter / fuel system diag‐

nostic pump - V144-

6 - Vacuum hose
7 - Connection hose

❑ Fuel system diagnostic

pump - V144- / air filter.

8 - Air filter
9 - 10 Nm
10 - Activated charcoal filter

❑ Location: in rear right

wheel housing.

❑ To remove, unscrew se‐

curing bolts and pull ac‐

tivated charcoal filter

downwards out of re‐

tainer.

11 - Breather line

❑ To activated charcoal fil‐

ter solenoid valve 1 -

N80-

❑ Clipped onto fuel tank

12 - Breather line

❑ From fuel tank

395

11.2.2

Assembly overview - activated charcoal filter system (vehicles with addi‐

tional filter)

1 - Fuel system diagnostic

pump - V144-
2 - Vacuum line
3 - Vacuum hose
4 - Connection hose
5 - Clip
6 - Breather line

❑ From fuel tank

7 - Clip
8 - Connection hose

❑ Fuel system diagnostic

pump - V144- / air filter.

9 - Securing bolt
10 - Air filter
11 - Additional filter
12 - 10 Nm
13 - Breather line

❑ To activated charcoal fil‐

ter solenoid valve 1 -

N80-

❑ Clipped onto fuel tank

14 - Connection hose
15 - Activated charcoal filter

❑ Location: in rear right

wheel housing.

❑ To remove, unscrew se‐

curing bolts and pull ac‐

tivated charcoal filter

downwards out of re‐

tainer.

16 - Securing bolts

11.3

Checking fuel tank breather (engine co‐

des BZB, CAWA, CAWB, CGYA, CCZA,

CCZB, CCZC, CCZD, CDAA, CDAB)

Special tools and workshop equipment required

Rep. gr.20 - Fuel supply system

♦ Hand operated vacuum pump - VAS 6213-

Test sequence
– Pull off breather line -2-. To do this, press release button. (col‐

our marking: white)

– Then connect hand vacuum pump - VAS 6213- as shown to

breather line.

– Move slide ring -1- on hand vacuum pump - VAS 6213- to po‐

sition -A- for “vacuum”.

– Operate hand vacuum pump - VAS 6213- several times. There

must be no development of vacuum.

397

– Seal breather hole on activated charcoal filter -arrow- and op‐

erate vacuum pump several times again. Vacuum must build

up.

11.4

Check fuel system for leaks (engine co‐

des CBFA, CCTA, CCTB)

Special tools and workshop equipment required
♦ Fuel system tester (so-called smoke tester) - KLI 9210-
♦ Adapter hose - KLI 9210/55-1-
♦ Vehicle diagnostic tester
♦ Hose clamps to 25 mm - 3094-

The plug-in connectors for fuel, vacuum and breather lines are

colour coded. There is either a coloured dot on the plug-in con‐

nector or the release button is coloured.

Plug-in connector

Colour code on plug-in connec‐

tor

Fuel supply

black

Fuel return

blue

Breather

white, beige

Vacuum

green

Test specification:
• A leak has been detected by the fuel system diagnostic pump

- V144- .

• Guided fault finding has been performed with the vehicle di‐

agnostic tester .

Preparation of fuel system tester - KLI 9210- :

Note

The fuel system tester - KLI 9210- may differ in appearance de‐

pending on the version.

Rep. gr.20 - Fuel supply system

– Check on fuel system tester - KLI 9210- if there is enough fluid

in smoke generator.

– Set valve -D- to “Hold”.
– Open nitrogen bottle -H-.
– Connect test hose -G- to self-test connection -B-.
– Set valve -D- to “Test”.
– Regulate pressure to 10 in. H2O (25 mbar) with pressure re‐

ducer -J-.

– Set valve -D- to “Hold”.
– Now pressure must be maintained for at least 2 minutes.

Check tester if pressure is not maintained.

Checking fuel system for leaks:

– Connect adapter hose - KLI 9210/55-1- to breather line -A-.

(colour marking: white)

– Connect measuring hose -G- from fuel system tester - KLI

9210- to adapter hose - KLI 9210/55-1- .

– Set valve -D- to “Hold”.

399

– Connect vehicle diagnostic tester to vehicle.
– Start engine and run at idling speed.
– On vehicle diagnostic tester , select operating mode

Guided

Functions

– Select guided function “Checking tank ventilation system for

leaks”.

– Initiate test.
– Observe pressure gauge - KLI 9210- while test is running.
• Fuel system diagnostic pump - V144- must pump up pressure

in fuel system to at least 7 in. H2O (18 mbar).

The minimum pressure was not reached, but the available pres‐

sure does not drop.
– Switch off ignition and perform a pressure retention test

⇒ page 400

. If no pressure drop can be detected: Check

vacuum supply of fuel system diagnostic pump - V144-

⇒ page 404

The minimum pressure was not reached and the available pres‐

sure drops immediately:

– Clamp off hose to activated charcoal filter solenoid valve 1 -

N80- using a hose clip -arrow-.

– Repeat check. If the minimum pressure is reached now, renew

activated charcoal filter solenoid valve 1 - N80- .

If the minimum pressure was again not reached and the available

pressure drops immediately:
– Leak in fuel system: Perform “leak detection in fuel system”

⇒ page 402

Switch off ignition if the minimum pressure is reached.
The valve in the fuel system diagnostic pump - V144- closes and

the pressure is retained.
– Observe pressure gauge:
If the pressure does not drop at first, perform a pressure retention

test to localise any potential small leaks

⇒ page 400

If the pressure drops, clamp off hose to activated charcoal filter

solenoid valve 1 - N80- using a hose clip -arrow-.
– If the pressure does not drop again, renew activated charcoal

filter solenoid valve 1 - N80- .

If the pressure still drops, perform “leak detection in fuel system”

⇒ page 402

Pressure retention test

Rep. gr.20 - Fuel supply system

– Set valve -D- to “Test”. Set the available pressure to 10 in. H2O

(25 mbar).

– Observe pressure gauge -C- and flow meter -E-. When the

throughput quantity decreases and the pressure increases to

10 in. H2O (25 mbar), the fuel system is filled.

Note

Depending on the filling level of the fuel tank, this process can

take up to 3 minutes.

– Once pressure has stabilised, set valve -D- to “Hold”.
• After 5 minutes the pressure must remain at or above 8 in.

H2O (20 mbar).

If the pressure is not held for at least 5 minutes, localise leak as

follows:

– First check activated charcoal filter solenoid valve 1 - N80- for

leaks. To do this, clamp off hose to activated charcoal filter

solenoid valve 1 - N80- using a hose clip -arrow-.

– Repeat pressure test by setting valve -D- again to “Test”.
– Observe pressure gauge and flow meter. When the through‐

put quantity decreases and the pressure increases to 10 in.

H2O (25 mbar), the fuel system is filled.

– Once pressure has stabilised, set valve -D- to “Hold”.
– If the pressure does not drop again, renew activated charcoal

filter solenoid valve 1 - N80- .

If the pressure still drops, perform “leak detection in fuel system”

⇒ page 402

After completing work, perform guided function “checking fuel

tank ventilation system for leaks” using vehicle diagnostic tester .

401

11.4.1

Leak detection in fuel system

Test specification:
• Procedure for “checking fuel system for leaks” has been com‐

pleted

⇒ page 398

• Fuel system tester - KLI 9210- is connected to vehicle via

adapter hose - KLI 9210/55-1- .

– Connect fuel system tester - KLI 9210- to vehicle battery.
– Remove rear right wheel housing liner.

– Clamp off hose between fuel system diagnostic pump - V144-

and air filter -arrow-.

Rep. gr.20 - Fuel supply system

– Set valve -D- to “Test”.
– Observe pressure gauge -C- and flow meter -E-. When the

throughput quantity decreases and the pressure increases to

10 in. H2O (25 mbar), the fuel system is filled.

– Once pressure has stabilised, set valve -D- to “Hold”.
• After 5 minutes the pressure must remain at or above 8 in.

H2O (20 mbar).

– If the pressure no longer drops, renew fuel system diagnostic

pump - V144- .

If the pressure is not held for at least 5 minutes or does not build

up, localise leak as follows:
– Fill fuel system with smoke, set valve -D- again to “Test” for

this.

– While fuel system is being filled, press button -I- for smoke

generator for approx. one minute.

The fuel system is now pressurised and filled with smoke.
– Check whether smoke escapes from any fuel system line or

hose. Also check fuel tank cap.

Note

♦

Light up the components and hoses with a strong floodlight. In

the floodlight, smoke is more visible.

♦

For leak detection in accessible areas, also use ultrasonic

meter or commercially available leak detector spray.

♦

Depending on how long the fault finding takes, it may be nec‐

essary to press the smoke generator button from time to time.

This ensures that sufficient smoke is present in the fuel sys‐

tem.

♦

To inspect flanges for fuel pump and fuel filter, open assembly

opening in vehicle interior.⇒ Vehicle diagnostic tester

– Renew leaking hoses or components.
After completing work, perform guided function “checking fuel

tank ventilation system for leaks” using vehicle diagnostic tester .

11.4.2

Schematic overview of activated charcoal filter system

403

1 - Activated charcoal filter
2 - Location of adapter hose -

KLI 9210/55-1-

❑ For leak detection in fuel

system

3 - Activated charcoal filter sol‐

enoid valve 1 - N80-
4 - Breather line

❑ Throttle valve module -

J338-

5 - Solenoid valve

❑ For fuel system diagno‐

sis pump - V144- .

6 - Vacuum line

❑ To intake manifold

7 - Air filter

❑ For fuel system diagno‐

sis pump - V144- .

8 - Fuel system diagnostic

pump - V144-
9 - Fuel
10 - Cap

11.4.3

Checking vacuum supply of fuel system

diagnostic pump - V144-

Special tools and workshop equipment required
♦ Turbocharger tester - V.A.G 1397A-

♦ T-piece - 251 201 346-
♦ Hose ∅ 6mm

Rep. gr.20 - Fuel supply system

Note

The fuel system diagnostic pump - V144- is fitted in the rear right

wheel housing behind the wheel housing liner.

– Remove rear right wheel and wheel housing liner.
– Pull off vacuum line -1- from fuel system diagnostic pump -

V144- .

– Connect turbocharger tester - V.A.G 1397A- with T-piece and

hose ∅ 6mm, between vacuum line -1- and fuel system diag‐

nostic pump - V144- -2-.

– Switch on measuring range

(absolute pressure measure‐

ment).

– Connect vehicle diagnostic tester and start engine.
– On vehicle diagnostic tester , select operating mode

Guided

Functions

– Select guided function “Checking tank ventilation system for

leaks”.

– Initiate test.
– Observe display on turbocharger tester - V.A.G 1397A- while

test is running.

• Pressure must pulsate and must remain at or below 0.7 bar

(absolute pressure) during test.

– If pressure exceeds 0.7 bar during test, vacuum supply is too

low. Check vacuum line to intake manifold for possible kinks

or blockages.

405

Activated charcoal filter system (Golf,

Eos, Scirocco with engine codes CA‐

WA, CAWB, BZB, CGYA, CCZA,

CCZB, CDAA)

Assembly overview - activated charcoal filter system

⇒ page 406

Checking fuel tank breather

⇒ page 407

Note

♦

Hose connections are secured with either spring-type or

clamp-type clips.

♦

Spring-type clip pliers - VAS 6340- or space saving hose clip

pliers - VAS 6362- are recommended for installing and remov‐

ing spring-type clips.

The plug-in connectors for fuel, vacuum and breather lines are

colour coded. There is either a coloured dot on the plug-in con‐

nector or the release button is coloured.

Plug-in connector

Colour code on plug-in connec‐

tor

Fuel supply

black

Fuel return

blue

Breather

white, beige

Vacuum

green

12.1

Assembly overview - activated charcoal filter system

Rep. gr.20 - Fuel supply system

1 - Activated charcoal filter

❑ Location: on right in en‐

gine compartment.

2 - Pressure retention valve

with connecting hose
3 - Connection hose

❑ Ensure firm seating
❑ From fuel tank

4 - 10 Nm
5 - Activated charcoal filter sol‐

enoid valve 1 - N80-

❑ Valve closed with igni‐

tion switched off

❑ When engine is warm,

valve will be activated

(pulsed) by engine con‐

trol unit

6 - Connection hose

❑ To intake manifold
❑ Ensure firm seating

7 - Bracket

❑ For activated charcoal

filter.

8 - Vent hole

12.2

Checking fuel tank breather

Special tools and workshop equipment required
♦ Hand operated vacuum pump - VAS 6213-

CDAA)

407

♦ Pressure gauge - VAS 6550-

♦ Connecting nipple - VAS 6550/3-1-
Test specification:
• Ignition must be switched off.
Test sequence
– Pull off bleeder line -1-.

– Connect hand vacuum pump - VAS 6213- with connection

nipple - VAS 6550/3-1- to breather line leading to activated

charcoal filter.

– Move slide ring -1- on hand vacuum pump - VAS 6213- to po‐

sition -A- for “vacuum”.

– Operate hand vacuum pump - VAS 6213- several times. There

must be no development of vacuum.

If vacuum builds up:
– Check breather hole on activated charcoal filter

⇒ Item 8 (page 407)

for soiling and clean if necessary.

If vacuum does not build up:

Rep. gr.20 - Fuel supply system

Volkswagen 4-cyl. injection engine (1.8 and 2.0 l engine, chain drive). Manual (Edition 08.2018) - page 13