Injector and Fuel Nozzle Test Equipment for Gasoline and Diesel Engines

Frequently Asked Questions About Injector and Fuel Injector Testers

Manual injector and fuel injector testers allow for the testing of opening pressure, spray pattern, leak tightness, and chattering characteristics of suitable gasoline and diesel fuel injectors. They are used in particular for the rapid mechanical-hydraulic evaluation and adjustment of fuel injectors. Here, we answer frequently asked questions about their selection and use.

• What can be tested using an injector tester?

  Using a suitable manual fuel injector tester, the following characteristics—in particular—can be tested depending on the type of injector:

  • Opening pressure
  • Spray pattern
  • Leakage
  • Dripping
  • Pressure drop
  • Rattling

  This allows for the detection of various mechanical and hydraulic abnormalities in a fuel injector.

  Which tests are permissible and meaningful depends on the specific injection system and the manufacturer’s specifications.

• What is the opening pressure of an injection nozzle?

  The opening pressure is the pressure at which a mechanically operated fuel injector opens and fuel flows out through the injector orifices.
  
  With suitable injectors, this pressure can be built up using a manual injector tester and read on a pressure gauge.
  
  If the measured opening pressure falls outside the manufacturer’s specifications, adjustment, maintenance, or further testing may be required, depending on the injector design.
  
  The specified values for the respective injector must be obtained from the manufacturer’s technical information.

• What does the spray pattern of an injection nozzle tell us?

  The spray pattern shows how the test fluid exits the nozzle orifices and is distributed.

  A uniform spray pattern that matches the nozzle design is an important prerequisite for proper fuel atomization.

  Abnormalities may include, for example:

  • an uneven spray pattern
  • individual deviating jets
  • lateral spray
  • dripping
  • clogged nozzle orifices

  The spray pattern must always be evaluated in accordance with the intended nozzle design and the manufacturer’s specifications.

• What does the “chatter” characteristic of an injection nozzle mean?

  With certain mechanical diesel injection nozzles, rapid operation of the test device causes a characteristic noise or vibration in the nozzle needle.
  
  This behavior is often referred to as “chirping.”
  
  A consistent buzzing pattern can provide indications of the nozzle needle’s mobility and function. An absence of buzzing or unusual behavior may indicate, for example, contamination, stiffness, or wear.
  
  The assessment depends on the specific nozzle design.

• How is the tightness of an injection nozzle tested?

  For the leak test, the tester is used to build up a defined pressure without the fuel injector opening as normal.
  
  The tester then monitors whether test fluid leaks from the injector tip, whether droplets form, or whether the built-up pressure drops at an impermissible rate.
  
  A leaky fuel injector can lead, among other things, to dripping and poor combustion performance.
  
  The test pressure and test duration must comply with the specifications for the respective fuel injector.

• Can common-rail injectors also be tested using a manual test device?

  Only to a limited extent and depending on the specific test device and injector.

  Suitable Leitenberger injector test devices can, for example, be used for static leak testing of certain common-rail injectors. Among other things, this allows for the assessment of droplet formation or pressure drop.

  However, such a test does not replace a complete functional test of a modern common-rail injector.

  Common-rail return flow testers are available for evaluating the return flow rate. A more comprehensive test of different operating points, injection volumes, and electrical control is performed on an injector test bench.

• What is the difference between a fuel injector tester and a common-rail injector test bench?

  A manual fuel injector tester generates the test pressure using a hand pump. It is particularly suitable for testing mechanical and hydraulic properties such as opening pressure, spray pattern, and leak tightness.

  An injector test bench, on the other hand, operates automatically and simulates defined test conditions for modern electronically controlled injectors.

  Depending on the test bench, various operating points, injection volumes, return volumes, spray patterns, and electrical functions can be tested and documented.

  For modern common-rail and gasoline direct-injection injectors, the test bench therefore offers significantly more comprehensive diagnostic capabilities.

• What is the advantage of a drag pointer on a pressure gauge?

  A lag pointer remains at the maximum pressure value reached.
  
  This makes it easier, for example, to read the opening pressure reached during a brief pressure spike, even if the pressure gauge pointer drops back down immediately afterward.
  
  This is particularly helpful during rapid manual test procedures.
  
  Leitenberger offers various injection nozzle testers, available with or without a lag pointer.

• What measurement range does an injection nozzle tester require?

  The required measurement range depends on the fuel injector being tested and the intended test procedure.
  
  Leitenberger offers manual test units with various measurement ranges, from low pressures up to 1,600 bar.
  
  A wider measurement range is not necessarily better. For an accurate reading, the measurement range should match the actual test pressure expected.
  
  Furthermore, the test device must only be used within its permissible operating and measurement ranges.

• Why are there test units rated at 400, 600, and 1,600 bar?

  Different injection systems and injectors operate at very different pressures.
  
  A device rated at 400 or 600 bar may be suitable for numerous conventional gasoline and diesel injectors.
  
  For certain diesel applications, devices with higher measurement ranges are available. The Leitenberger DET 1000, for example, has a measurement range up to 1,600 bar.
  
  Which device is suitable depends on the specific injection nozzle and the intended test.

• What test fluid should be used for the injector test?

  Only a test fluid that is suitable and intended for the specific test procedure should be used for the test.
  
  The fluid must be clean and must not damage the test equipment, the seals, or the injector.
  
  Contaminated test fluid can affect nozzle openings and sensitive components, thereby distorting the test results.
  
  The specifications of the test equipment and injector manufacturers must therefore be followed.

• Can you check right after cleaning to see if the spray pattern has improved?

  For injection nozzles suitable for this purpose, it may be advisable to perform another test after cleaning or maintenance.
  
  This allows, for example, the opening pressure, spray pattern, and leak tightness to be compared before and after the procedure.
  
  However, an improvement in the spray pattern alone does not prove that the injector is fully functional under all operating conditions.
  
  For modern electronically controlled injectors, additional testing on an injector test bench may be necessary.

• What safety rules apply to manual fuel injector tests?

  Manual fuel injector testers can also generate very high pressures.

  The liquid jet must never be directed at people or any part of the body. Liquid ejected under high pressure can cause serious injury.

  During the test, the following must also be ensured:

  • Appropriate splash protection must be used,
  • Hoses and connections must be undamaged,
  • The injector or fuel injector must be securely fastened,
  • Only suitable test fluid may be used,
  • Operating and safety instructions must be followed.