Fuel Delivery and Air Induction: Testing and Inspection

WM 200101 Checking fuel system (high-pressure side) for leaks

Tools









Technical values






Information

Requirements

If only the high-pressure pump is removed and installed, the intake manifold must be removed for leak testing.
1. Battery disconnected.
2. Air cleaner housing removed.
-> 242519 Removing and installing air cleaner housing.
3. Resonance tube removed.
-> 247419 Removing and installing resonance tube.
4. Intake-air distributor removed.
-> 244619 Removing and installing intake-air distributor.

Checking

Component overview

CAUTION

Dirt on injection system components (intake manifold injection and direct fuel injection system)

- Material damage
- Rough-running engine
- Bad exhaust emissions

-> Thoroughly clean connection points and adjacent areas before loosening them. If the engine is very dirty, wash it before starting disassembly work.
-> Lay removed parts on a clean surface and cover them. Only use a clean, lint-free cloth.
-> Carefully cover components or seal them if repair work will not be carried out immediately. Place rubber caps on connections. Seal intake openings with film or adhesive tape.
-> Only install clean parts. Do not take spare parts out of the packaging until just before installation.
-> Never use compressed air when the system is open. Do not move the vehicle.

Information

- Always perform a leak test in the high-pressure area after opening the fuel system.

- This is particularly important if components are disassembled and replaced.

- The threaded connections of the fuel lines must be coated with OKS 1710 lubricant (Part No. 000.043.303.27) before being screwed back on again.

- Blow residual fuel out of the lines and high-pressure pump (into a fuel-resistant container or cloth) using compressed air before installation.

- The tightening specifications must be strictly observed.

Overview of fuel system in engine compartment





Component overview of fuel system at engine





Leak test on high-pressure side

Information

- Check that the tool fittings are clean before starting the leak test.

- Blow out the tool fittings before assembly using gentle bursts of pressure to prevent dust and foreign bodies from getting into the high-pressure system during the leak test.

- Ensure that the tools for the leak test remain clean and free of dirt when stored.

Tools:





Tools





CAUTION

Incorrect test results will be obtained by unapproved test gases!

- Risk of leaks if the WRONG TEST MEDIA (air, petrol, water, etc.) are used!

-> Only the approved test media guarantee comparability with fuels at pressures of up to 10 bar.
-> The leak test media, which are used for technical purposes, are supplied as compressed gas in compressed gas bottles.

Materials: Approved
test media





WARNING

Highly inflammable or explosive materials

- Danger of fire or explosion

-> Avoid contact with hot parts or sources of ignition.
-> Use suction to remove ignitable vapours.
-> Attach warning sign in a clearly visible position.

1. Attach warning sign in a clearly visible position on the vehicle or position in the immediate working area.





Example of warning sign

WARNING

Leaking fuel supply lines

- Emerging fuel
- Risk of fire

-> Perform leak test.

2. Connect adapter hose to rapid-action coupling of low-pressure line -arrow-.
2.1. Connect air connection of filling unit -2- to adapter -1-.





Adapter connection in engine compartment

3. Fit pressure reducer -2- onto gas bottle and connect to connecting line of filling unit -3-.
3.1. Check threaded connections on pressure reducer are seated securely.
3.2. Check air adapter is seated securely -4-.
3.3. Screw gas bottle onto screw plug -1- anticlockwise by 2-3 turns.





Connecting tester

CAUTION

Test pressure is exceeded

- Risk of damage to high-pressure pump

-> The test gas test pressure must not exceed a maximum pressure of 10 bar.
-> The setting is made at the pressure reducer.

4. Set the test pressure on the pressure reducer to between 7 and 9 bar (corresponds to a flow volume of approx. 26 - 28 liters of test gas -arrow- ).





Adjusting pressure reducer settings

5. Using the test gauge -1- apply the ideal pressure to the closed fuel system.





Test gauge

=> Pressure: 8 bar+/-1 bar
6. Coat connections with commercially available leak-locating spray (see recommendation).
6.1. Leaks are identifiable from bubbling and can also be heard as a hissing sound.
6.2. There must be no pressure drop at the test gauge.
7. Leaks could be caused by a damaged sealing cone, loose connections or incorrectly fitted union nuts (damaged thread), for example.
7.1. Determine causes and correct immediately.
8. Remove test tools.
8.1. The test gases evaporate after a short time.

Subsequent work

1. Install intake-air distributor.
-> 244619 Removing and installing intake-air distributor.
2. Install resonance tube.
-> 247419 Removing and installing resonance tube.
3. Install air cleaner housing.
-> 242519 Removing and installing air cleaner housing.
4. Use PIWIS Tester 9718 to bleed the high-pressure system using the First Start function.
5. Perform a test drive. A high-pressure adaptation is only necessary if the high-pressure pump has been replaced.
-> 247019 Removing and installing DME (DFI) control unit.