1997 AUDI A4 EVAP Workshop Manual

Setting mode.

VAS 5051 should immediately indicate "System
OK"

- Repeat test several times to verify result.

If test continues to indicate "System OK",
remove clamp and proceed to "Test EVAP
System".
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If VAS 5051 indicates "System not OK":

- Replace LDP and repeat test.

If VAS 5051 indicates "System OK" after LDP is
replaced and test result is verified:

- Perform quality check and return vehicle to
customer.

Test EVAP System
Also Page 20
-134
.
If vehicle is not LDP-equipped:

- Plug or clamp EVAP canister outlet and proceed
to step "Continued for all vehicles" (below).
If vehicle is LDP-equipped:

- Plug or clamp LDP inlet (filter side) using
Special Tool No. 3094 or equivalent.
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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).
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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.
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Method 2: Locate leak with ultrasonic tester
If leak cannot be located:
CAUTION!
Clamp only soft rubber lines when isolating a leak. To avoid risk of
damage, never clamp hard plastic lines! General search: tester only
Localized search: tester with extension (on left in illustration)
- Disconnect and plug or clamp shut EVAP lines to isolate fuel tank,
using Special Tool No. 3094 or equivalent, before continuing.
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If flow stops:

- Reconnect EVAP lines to search area that was
isolatedl
If leak or source of fuel odor cannot be found:

- Contact Audi Dealer Technician Helpline.

CAUTION!

Under no circumstances should the vehicle
be returned to the customer without proper
diagnosis and repair.
When leak has been located:

- Repair leak and repeat EVAP system test.

- Perform quality check and return vehicle to
customer.

Note:

Because leak may be at top of fuel tank, it may
not be possible to locate through fuel
pump/sending unit access plate.
Fuel tank may need to be lowered to locate the
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leak.
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EVAP system leak detection circuit,
schematic diagram (vehicles with 1.8 ltr.
turbo engine)

Repair Manual, 1.8 Liter 4-Cyl. 5V Turbo Fuel
Injection & Ignition, Repair Group 24 1 -
Check valve
Location (light/dark side): as shown in
illustration
2 -
EVAP canister purge regulator valve -N80-Location: in engine compartmentChecking
3 -
Bleed line
From EVAP canister purge regulator valve
-N80-
LocationRight side under floor panFront-wheel drive: on floor pan in area of
fuel tank All-wheel drive: on fuel tank in area of fuel
tank
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