Volkswagen Golf Service & Repair Manual: Checking fuel system for leaks

Special tools and workshop equipment required

Fuel system tester (so-called smoke tester) -KLI 9210-

Adapter hose -KLI 9210/55-1-

Hose clamps up to 25 mm -3094-

Plug-in connector	Colour code on plug-in connector
Fuel supply	Black
Fuel return line	Blue
Breather	White or beige

Preparation of fuel system tester -KLI 9210-:

Note The fuel system tester -KLI 9210- may differ in appearance depending on the version.

Check fuel system tester -KLI 9210- to ensure that 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 25 mbar (10 in H₂O) with pressure reducer -J-.
Set valve -D- to “Hold”.

Pressure must now 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 lines -A-“white marking” as shown.

Connect measuring hose -G- from fuel system tester -KLI 9210- to adapter hose -KLI9210/55-1-.
Connect fuel system tester -KLI 9210- to vehicle battery.
Remove rear right wheel housing liner.

Tightly seal hose to air filter -arrow- using a hose clamp.

Set valve -D- to “Test”. Fuel system will now be filled.
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 not drop below 8 in. H2O (20 mbar).

If pressure drops or pressure fails to build up, localise leak as follows:

Fill fuel system with smoke. To do this, set valve -D- to “Test” again.
While fuel system is being filled, depress button -I- for smoke generator for approx. one minute.

The fuel system is now pressurised and filled with smoke.

Check all lines and hoses and sealing cover of fuel system for escaping smoke.

Note Illuminate all components and hoses with a powerful light to make the smoke easier to detect. For leak detection in accessible areas, the ultrasonic tester or commercially available leak-detecting spray can also be used. Depending on how long fault finding takes, it may be necessary to press the smoke generator button from time to time. This ensures that sufficient smoke is present in the fuel system.

To inspect flanges for fuel pump and fuel filter, assembly opening in vehicle interior must be opened.

Renew leaking hoses or components.

Checking fuel system for leaks