Checking Fuel System For Leaks

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. 

1. Fit hose connection -4-  and adapter VAG 1318/11 -3-  to a suitable fuel test line -1-  .

   Tighten hose clamps -2-  .

   Fig 1: Identifying Hose Connection

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   Fig 2: Identifying Adapter VAG

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   Fig 3: Identifying Test Adapter

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2. Unclip fuel supply line -1-  at the high-pressure pump -2-  . Absorb escaping fuel.
   Fig 4: Identifying High-Pressure Pump

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3. Clip in test adapter -4-  on the high-pressure pump.
   1. 3.1. Check that the test adapter is fitted correctly.
      Fig 5: Identifying Test Adapter

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   NOTE: Test pressure is exceeded

   • Risk of damage to high-pressure pump

   → The test gas test pressure must be set to less than → Pressure: 10 bar  on the pressure reducer on the test gas bottle.

   WARNING: Working with compressed air

   • Risk of eye injuries
   • Risk of damaging and dirtying components

   → Wear protective goggles with side eye protection.

   → Protect the point at which the compressed air emerges with suitable material.

   → Place the point at which the compressed air emerges on suitable surfaces.

   Information 

   The use of unapproved test gases results in incorrect test results. Only approved test gases guarantee comparability with fuel high-pressure systems at pressures of up to 10 bar  .

4. Fit test gas bottle with pressure reducer and air-spring strut filling unit VAS 6231 WE 1282  securely so that no gas can escape → Test equipment setup  . Set pressure reducer to max. 10 bar pressure → Adjusting pressure reducer to between 7 and 9 bar of test gas pressure  .
   Fig 6: Identifying Filling Unit VAS

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   Fig 7: Identifying Test Equipment

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   Fig 8: Adjusting Pressure Reducer To Between 7 And 9 Bar Of Test Gas Pressure

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5. Air-spring strut filling unit VAS 6231 WE 1282  must then be connected to the adapter 9759  (-1-  ). Tighten the connection if necessary.
   Fig 9: Connecting Test Adapter

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6. Depending on the high-pressure connections that were loosened (removed fuel distributor pipe or removed high-pressure pump), complete the following steps =>

   If the fuel distributor pipe (high-pressure rail) was removed =>

7. Before screwing the fuel distributor pipe (high-pressure rail) to the engine, quickly blow out residual fuel from the high-pressure pump and high-pressure line (intake) to the high-pressure rail.
   1. 7.1. Apply a quick burst of pressure using the filling unit and blow residual fuel out of the high-pressure pump and high-pressure line. Absorb escaping fuel. → Blowing out high-pressure line (similar illustration) 
      Fig 10: Blowing Out High-Pressure Line

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   2. 7.2. Drain residual fuel from the high-pressure distributor pipe before fitting it. Absorb escaping fuel.
8. Fit high-pressure distributor pipe (high-pressure rail) and tighten it to the correct tightening torques. → INSTALLING FUEL COLLECTION PIPE
   NOTE: Test pressure is exceeded

   • Risk of damage to high-pressure pump

   → The test gas test pressure must be set to less than → Pressure: 10 bar  on the pressure reducer on the test gas bottle.

9. Use air-spring strut filling device VAS 6231 WE 1282  to apply test gas pressure of between 7 and just under 10 bar to the completely fitted high-pressure system -2-  . The pressure is distributed slowly in the system and can increase slightly on the pressure gauge. If there is a constant drop in pressure, there is a leak in the system.
   Fig 11: Connecting Test Adapter

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10. Spray all connection points in the high-pressure system with commercially available leak-locating spray. If the pressure drops even though the threaded joints are perfectly sealed, also spray the soldered joints and connecting pipes as well as the high-pressure pump and test equipment with leak-locating spray.
11. If there is a leak, gently sashaying  , moving and growing  air bubbles → Leak (similar illustration)  will emerge. These could be caused by a damaged seal, loose connections or incorrectly fitted union nuts, for example. The cause must be determined and corrected.
    Fig 12: Checking Air Bubbles Leak

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    If the high-pressure pump was removed =>

12. Before screwing the high-pressure line (intake) to the high-pressure pump, residual fuel must be blown out of the high-pressure pump.
    1. 12.1. Apply a quick burst of pressure using the filling unit and blow any fuel out of the high-pressure pump → Blowing out high-pressure pump (similar illustration)  . Absorb escaping fuel. → Blowing out high-pressure pump (similar illustration) 
       Fig 13: Blowing Out High-Pressure Pump

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13. Screw high-pressure line correctly to the high-pressure pump. → INSTALLING HIGH-PRESSURE PUMP
    NOTE: Test pressure is exceeded

    • Risk of damage to high-pressure pump

    → The test gas test pressure must be set to less than → Pressure: 10 bar  on the pressure reducer on the test gas bottle.

14. Use air-spring strut filling device VAS 6231 WE 1282  to apply test-gas pressure of between 7 and just under 10 bar to the fitted high-pressure pump. The pressure is distributed slowly in the system and can increase slightly on the pressure gauge. If there is a constant drop in pressure, there is a leak in the system.
    Fig 14: Connecting Test Adapter

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15. Spray all connection points for the high-pressure pump with commercially available leak-locating spray. If the pressure drops even though the threaded joints are perfectly sealed, also spray other connection points as well as the high-pressure pump and test equipment with leak-locating spray.
16. If there is a leak, gently sashaying  , moving and growing  air bubbles will emerge (union nut on injector is shown) → Leak (similar illustration)  . These could be caused by a damaged seal, loose connections or incorrectly fitted union nuts, for example. The cause must be determined and corrected.
    Fig 15: Checking Air Bubbles Leak

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