Leak Testers for Fuel Tank Systems

Frequently Asked Questions About Leak Testing of Fuel Tank Systems

Fuel tanks, lines, and connections must be reliably leak-free again after repairs or after the fuel system has been opened. Using a suitable fuel system leak tester, the system can be pressurized to a specified low test pressure and checked for pressure loss.

• When should a fuel tank system be checked for leaks?

  A leak test is particularly advisable or necessary if the fuel system has been opened or one of its components has been removed.

  Typical applications include, for example:

  • Removal or replacement of the fuel tank
  • Work on fuel lines
  • Replacement of fittings or gaskets
  • Repairs to the fuel filler neck
  • Work on fuel-carrying components
  • Suspected leak
  • Final inspection after a repair

  The type of test required after a repair depends on the vehicle manufacturer’s specifications.

• What is checked during a leak test of the tank system?

  The test verifies whether the connected fuel supply system maintains a specified low test pressure.

  If the pressure drops during the specified test period, there may be a leak in the fuel system or in the test setup.

  Possible leak points include, for example:

  • Tank
  • Fuel filler neck
  • Pipes
  • Hose connections
  • Quick-connect couplings
  • Gaskets
  • Caps
  • Other components belonging to the system under test

  Before making an assessment, you should always rule out the possibility that the adapter or the test connection itself is leaking.

• How does a fuel tank leak test work?

  The test device is connected to the fuel supply system using a suitable adapter.
  
  Depending on the vehicle, the connection can be made, for example, via the fuel filler neck or a suitable quick-connect fitting.
  
  A specified low test pressure is then established. Afterward, the system checks whether the pressure remains stable within the specified test period.
  
  The specific test procedure must comply with the vehicle manufacturer’s specifications and the test device’s operating instructions.

• At what pressure is the tank system tested?

  On the Leitenberger TSD_03_LR and TSDD_03_LR tank system leak testers, the test pressure is fixed at 20 mbar.
  
  This deliberately low test pressure is designed for the intended tank system testing.
  
  A higher pressure must not be used without authorization. Tanks, vent lines, and other components are not comparable to high-pressure systems and can be damaged by an inappropriate test pressure.

• Why is the test pressure set to a fixed value?

  A fixed test pressure reduces the risk of accidentally setting the pressure too high during use.
  
  This makes the test procedure more reproducible and protects the tank system from incorrect operation due to excessive test pressure.
  
  Nevertheless, the specifications of the respective vehicle manufacturer must also be observed.

• Where is the leak tester connected to the vehicle?

  Depending on the vehicle, the connection can be made via the fuel filler neck or via a suitable quick-connect fitting near the fuel system.
  
  This requires a test adapter that is compatible with the vehicle or the connection point.
  
  The choice of connection depends on the vehicle's design and the prescribed test procedure.

• Is a special fuel system test adapter required for each vehicle?

  It is not mandatory, but the adapter used must fit securely and tightly into the respective connection point.
  
  Autotestgeräte Leitenberger offers vehicle-specific test adapters for certain applications. Additional test and wiring adapters may be required depending on the vehicle.
  
  An adapter that does not fit properly can itself cause a loss of pressure and thus skew the test results.

• Are the tank system test adapters included in the scope of delivery?

  No. For Leitenberger tank system leak testers, vehicle-specific test adapters are not included in the standard scope of delivery.
  
  This allows the tester to be combined with the adapters required for the respective fleet of vehicles.
  
  Before purchasing, you should therefore determine which vehicles or tank systems are regularly serviced.

• What does a pressure drop mean during a tank system test?

  A drop in pressure may indicate a leak.

  However, before a vehicle component is deemed to be leaking, the entire test setup should first be checked.

  This includes, in particular:

  • Test adapters
  • Couplings
  • Test equipment hoses
  • Connection points on the vehicle
  • Gaskets

  Only after the test setup has been ruled out as the cause should the leak detection process on the vehicle continue.

• How can you then locate the leak?

  The pressure loss test initially indicates that the system being tested may not be leak-tight. However, it does not automatically pinpoint a small leak.
  
  The accessible components of the system must then be systematically inspected.
  
  Depending on the vehicle and the manufacturer’s specifications, additional leak detection methods may be required.
  
  The pressure test thus serves both as a final leak test and as a starting point for further leak detection.

• What is the difference between an analog and a digital fuel tank system tester?

  Both Leitenberger devices operate at a fixed test pressure of 20 mbar.
  
  The TSD_03_LR uses a conventional pressure gauge.
  
  The TSDD_03_LR, on the other hand, features a digital pressure gauge with a measurement range of -50 to +50 mbar.
  
  The digital display can be particularly advantageous when small changes in pressure need to be easily read and compared during the test.

• Is the fuel system leak test the same as a complete EVAP diagnostic test?

  Not necessarily.
  
  The leak test checks whether the connected fuel system maintains a specified test pressure.
  
  Modern vehicles may also have complex fuel tank ventilation and emission systems that include valves, activated carbon canisters, sensors, and control unit functions.
  
  Additional electrical, electronic, or vehicle-specific test procedures may be required for a complete diagnosis of these systems.
  
  Therefore, the pressure test should be considered part of the fuel system diagnosis and not automatically as a substitute for all EVAP tests specified by the vehicle manufacturer.

• Can the fuel system be inspected immediately after the fuel tank has been removed?

  A leak test is a typical procedure, especially after repairs or removal of the fuel tank.
  
  This allows you to check, either before or after the work is completed, whether the tank, connections, and attached lines have been reinstalled properly and are leak-free.
  
  The timing of the test and the necessary preparations depend on the vehicle manufacturer’s specific repair procedure.

• What safety rules apply when performing a leak test on a fuel system?

  Fuel and fuel vapors can be flammable. Therefore, care must be taken during every test.

  In particular, observe the following:

  • Avoid ignition sources
  • Ensure adequate ventilation
  • Use only approved test equipment and adapters
  • Do not exceed the permissible test pressure
  • Inspect lines and connections before testing
  • Follow the vehicle manufacturer’s and occupational safety guidelines

  The fuel system must not be pressurized with unsuitable high-pressure test equipment.

• Which Leitenberger tank system leak tester is the right one?

  The TSD_03_LR is available for basic testing with a fixed test pressure of 20 mbar.
  
  If a digital pressure display is also desired, the TSDD_03_LR with a digital pressure gauge is the ideal choice.
  
  For both devices, the adapters compatible with the respective vehicle or test connection must be selected separately.