Checking EVAP system for leaks

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2002 Volkswagen Jetta, 2002 Volkswagen GTI, 2001 Volkswagen Jetta, 2001 Volkswagen GTI, and 2000 Volkswagen Jetta. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Locating LDP Outlet (EVAP Side)

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Clamp off LDP outlet (EVAP side) - 1 - using hose clamps, up to dia 25 mm 3094 or equivalent.

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

Turn control valve from "Hold" to "Test".
Allow fuel system to pressurize.

NOTE:

Fuel system pressurization depends on volume of fuel system and amount of fuel in tank.

If fuel system pressurization does not stabilize:

Verify that all fuel system outlets have been sealed before continuing.

NOTE:

Any flow shown on flow meter indicates a leak. Flow below flow meter flag set at vehicle leak standard may indicate a sporadic DTC.

If flow meter on tester registers flow near or above pre-set pressure:

Clamp off hose leading from Evaporative emission (EVAP) canister purge regulator valve N80 to intake manifold.

If flow stops:

Replace Evaporative emission (EVAP) canister purge regulator valve N80 and repeat test before continuing.

If meter indicates no flow after test:

Perform quality check and return vehicle to customer.

If flow continues:

Use smoke generator trigger to charge fuel system with smoke again.
Inspect complete EVAP system for escaping smoke.

NOTE:

It may be necessary to move, twist, or wiggle EVAP components around to reproduce leak.

If leak cannot be found using smoke:

Fig 2: Ultrasonic Tester

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Locate leak with ultrasonic tester.

General search: tester only
Localized search: tester with extension wand (left)

If leak cannot be located:

Disconnect and plug or clamp shut EVAP lines to isolate fuel tank using Hose clamps, up to dia 25 mm 3094 or equivalent before continuing.

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

If flow stops:

Reconnect EVAP lines and search area that was isolated.

When leak has been located:

Repair leak and repeat EVAP system test.

NOTE:

Because leak may be at top of fuel tank, it may not be possible to locate through fuel pump/sending unit access plate.
Lower fuel tank if necessary to locate leak.

CAUTION: Do not return vehicle to the customer without having performed a proper diagnosis and repair.