fuel cap AUDI A4 1999 B5 / 1.G EVAP Workshop Manual

20-136

Fuel tank and EVAP system, checking
for leaks


Note:
In the following, individual questionable points
will be considered that could be leaks in the fuel
tank and tank ventilation system. After
eliminating a possible leak, it is effective to then
perform a tank leak diagnosis to determine
whether the leak was successfully sealed.

- Switch OFF ignition.

- Check if filler cap was completely closed for the
test.

- Check if filler cap seal is damaged or crimped,
replace if necessary.

- Check if the gaskets under the cover flanges are
OK and if the union nut on the fuel tank cover
flange is correctly tightened.

- Check hose connections for tightness and
integrity repair or replace as necessary.

- Remove luggage compartment trim.
Pa
ge 7 of 65 EVAP s
ystem, servicin
g
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE04.20.5

If vehicle fails above test ("System not OK"):

- Verify fuel cap is properly closed; repeat test.
Pa
ge 42 of 65 EVAP s
ystem, servicin
g
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE04.20.5

20-167
If "System OK" after re-test:

- Erase DTC memory (if necessary).

- Repeat test several times to ensure proper
EVAP system operation (remove and re-install
fuel cap before each test).

- Perform quality check and return vehicle to
customer.

Note:
If the vehicle passes the above EVAP system
test, DTCs may be sporadic; the entire EVAP
system should be carefully inspected.
If VAS 5051 continues to indicate "System not
OK" after re-test, proceed to next step.

Perform EVAP tester self-test

Note:

Always perform system self-test of KLI9210
EVAP Tester prior to use to ensure that there
are no leaks.
Refer to KLI9210 instruction manual for specific
instructions.
Pa
ge 43 of 65 EVAP s
ystem, servicin
g
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE04.20.5

20-169

Note:
If the leak cannot be located or repaired, contact
K-Line Customer Service - Technical Support.

Calibrate KLI9210 Tester
Determine vehicle leak threshold:

To m.y. 2000: leak threshold 0.040 in.

From m.y. 2001: leak threshold 0.020 in.

Test fuel cap - Attach test hose to appropriate preset port (black arrows).
- Turn control valve from "Hold" to "Test".
- Set flow meter flag (white arrow) at indicated value on flow meter.
- Turn control valve to "Hold"; remove test hose.
- Connect fuel cap tester to hose.

If no flow is indicated: - Screw fuel cap tightly to cap receiver (arrow).
- Turn control valve to "Test".
- Read flow meter on tester.
Pa
ge 46 of 65 EVAP s
ystem, servicin
g
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE04.20.5

20-170
If flow is indicated:

- Replace fuel cap and re-test.
If new fuel cap shows no flow:

- Repeat Leak Test, with new fuel cap installed,
using VAS 5051 and Basic Settings mode,
Page 20
-139
.
If Leak Test shows 'System OK":

- Perform quality check and return vehicle to
customer.

Test LDP -V144- for internal leaks
If vehicle is not LDP-equipped, proceed to "Test
EVAP system".

- Clamp off LDP outlet (EVAP side) using Special
Tool No. 3094 or equivalent.

CAUTION!

Clamp only soft rubber lines when isolating a
leak. To avoid risk of damage, never clamp
hard plastic lines!

-
Repeat Leak Test using VAS 5051 and Basic
Pa
ge 48 of 65 EVAP s
ystem, servicin
g
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE04.20.5

20-172


Note:
Fuel system pressurization depends on volume of fuel system and
amount of fuel in tank.
If fuel system pressurization does not stabilize:
CAUTION!
Clamp only soft rubber lines when isolating a leak. To avoid risk of
damage, never clamp hard plastic lines!
Note:
Any flow shown on flow meter indicates a leak. Flow before flow meter
flag set at vehicle leak standard may indicate a sporadic DTC.
If flow meter on tester registers flow near or above preset pressure: - Attach fuel cap adapter to filler neck (arrow) and test hose to adapter.
- Turn control valve from "Hold" to "Test".
- Allow fuel system to pressurize.
- Verify all fuel system outlets have been sealed before continuing.

- Clamp off hose (arrow) leading from EVAP purge regulator valve -N80-
to intake manifold (pictured: AHA engine in A6).
Pa
ge 51 of 65 EVAP s
ystem, servicin
g
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE04.20.5

20-173
If flow stops:

- Replace EVAP purge regulator valve -N80- and
repeat test before continuing.
If meter indicates no flow after test:

- Perform a quality check and return vehicle to
customer.
If flow continues, proceed as follows:

Method 1: Locate leak with smoke generator

- Connect leads from smoke generator to vehicle
battery.

- Use smoke generator trigger to charge fuel
system with smoke.

- Inspect complete EVAP system for escaping
smoke.
Pa
ge 52 of 65 EVAP s
ystem, servicin
g
11/18/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE04.20.5