Leak Testing Fuel Injector Components

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A vehicle’s fuel injection system is responsible for injecting fuel into the engine cylinders, where the gas is burned to produce engine power. A leaky fuel injector, which is a common fuel injection system problem, can significantly compromise engine performance and produce a variety of symptoms.

As described in this article on eHow.com, small things like an erratic engine idle, a misfiring engine, reduced gas mileage and worst case, an excessive fuel leak onto the hot surfaces of the engine intake manifold or engine block causing the fuel to ignite and cause an engine fire. These problems can be arrested in the first instance with accredited testing systems.

Faulty fuel injector components not only are a threat to the end-user / consumer’s life, they also make terrible testimonials to your quality control. That we know isn’t the ideal situation for a component manufacturer, be it of any size.

InterTech’s leak testing solutions offer you unsurpassed excellence in testing solutions, both leak and functional. Here’s one such solution that has helped many manufacturers of fuel injector components to test and verify leaks in their manufactured components.

The Challenge

Fuel injection components often demand 100% leak testing to limits as low as .01 sccm with cycles as fast as 2.5 seconds, 10% R&R quality requirements, while also displaying significant part temperature variations.

Separate tests with different limits are typically needed in the same test cycle for body welds, seat leakage, and overall leakage. Integration of instrumentation software, fixturing and test circuit is essential, as is complete test documentation.


Fuel Injector Test Fixture and Parts

Test Process and Solutions

InterTech’s downstream test process features a patented Micro-Flow mass-flow transducer to provide 10 times greater leak sensitivity than any other dry-air test method. A test part is enclosed within a test chamber and pressurized; leakage is measured as a flow increase into the test circuit outside the part, eliminating the need and time for pressure stabilization inside the part. The test circuit is precisely engineered for minimum volume, enabling the Micro-Flow sensor to almost instantaneously measure flows with a resolution of .0001 sccm.

Critical for fast small-leak testing, all fixtures and clamping devices are designed and built for absolute stability to prevent part movement during testing. Seal positioning mechanisms consistently address the test part squarely and firmly, stabilizing their closure forces quickly to shorten cycle times.

Seals are designed for high durability to run thousands of parts per day without replacement. With these unique features, Micro-Flow dry-air test systems deliver .01 sccm testing with less than 10% R&R.

Special Features

  • InterTech’s Patented Bias-Leak checking is especially important for fail-safe operation whenever testing to less than 1 sccm. It uses low-level airflow to confirm test-circuit integrity before each test cycle.
  • Temperature compensation sharpens test accuracy and repeatability by nullifying test part residual heat from welding, fabrication, washing or even operator handling. Custom algorithms based on the test part’s unique cooling characteristics supply appropriate corrective responses across the test cycle.
  • InterTech’s S-3085 networking/diagnostic software graphically visualizes for greater operator control the factors that can compromise a good baseline zero, trigger false rejects or otherwise disrupt accuracy and repeatability.

Follow the InterTech India blog for more solutions on leak and functional testing. For sales enquiries, you may contact us at;

Mobile: +91 994 032 0718

eMail: ajay@intertechdevelopment.com

Land phone: +91 44 4211 2525



InterTech M1075 – for unsurpassed leak testing speed and accuracy

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An InterTech Design Report

Our diesel engine mass flow technology shortens test cycle time by finding leaks faster to enhance manufacturing efficiency and process – significantly. Download the full report in a PDF format at:DR129_R1

The Challenge

Develop a production line solution to detect and repair leaks prior to hot testing. Eliminate the possibility of leak-associated defects getting through the system. Deliver accurate results in seconds, while not wasting time and money on hot test repeats.

InterTech M1075 – for unsurpassed leak testing speed and accuracy - using Mass Flow, Pressure Decay & Differential Pressure Testing

InterTech M1075 – for unsurpassed leak testing speed and accuracy

The InterTech Solution

InterTech M1075 dry air tests both the water side and the oil side of an engine block at the same time, up to twice as fast as other available options.

The water side includes engine block passages, water pump, heater housing, thermostat housing, associated hoses and the coolant half of the lube-oil cooler, creating a cavity of about 12 liters. The oil side includes engine block passages plus, front and rear gear fly wall housings, crankshaft seals, oil pan, intake manifold and the oil half of the lube-oil cooler.

This creates a cavity of up to 180 liters depending on engine model. The InterTech testing system avoids problems of pressure fluctuation in the supply line by using isolated air reservoirs. Because it is independent of plant air supply, it provides a direct and stable measurement of leakage.

The InterTech system simultaneously pressurizes both cavities and the reservoirs: the oil cavity to 2.5 psi with a reject limit range of .2 lpm to1.4 lpm (user selectable); and the water cavity to 10 psi with a reject limit of 25 sccm.

Any leakage causes the leaking cavity to lose pressure and the InterTech mass flow transducer reads the flow rate.


For a customised quote for your leak testing problems, contact our Indian office in Chennai at 044 – 4211 2525 / +91 994 032 0718 / +91 98409 14544

You may also email our Sales Reps in India at ajay@intertechdevelopment.com / ram@intertechdevelopment.com


Leak Testing 101 – Part 4

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In parts onetwo, and three of this “Leak Testing 101” series, we discussed three methods of dry-air leak testing—pressure decay, differential pressure decay, and mass-flow leak testing—including the pitfalls and hidden costs inherent in two-step pressure testing methods and the higher accuracy of single point measurement mass-flow leak testing techniques.

 Is mass-flow leak testing always the best leak testing method? Absolutely not. When accuracy and cycle time requirements are not that stringent, pressure decay testing or differential pressure decay testing can be a better application match because test instrumentation does not require as much specialization and related cost. At the other extreme, when very small leaks of less than 0.01 standard cubic centimeters per minute (sccm) must be detected, helium mass spectrometer leak testing methods may be required. It is the only reliable method when an application requires detecting leaks as small as 10–4 standard cubic centimeters per second (sccs) or less.

There are several different helium leak detection methods:

Sniffer—The test item is pressurized with helium and an operator moves a sniffer probe connected to the mass spectrometer to localize the leak. This method is slow, nonquantitative but has the advantage of localizing the leak.

Accumulation—The test item is placed in a chamber and charged with helium. Helium leaking from the part accumulates in the chamber and after a certain amount of time, a sniffer probe checks for the presence of helium, i.e., a leak. While apparently inexpensive, this method has a number of shortcomings: presence of tracer gas from prior tests, lack of adequate circulation in the chamber, and long test times due to background effects. As a result, it will be difficult to provide quantitative testing with this method.

Vacuum leak testing with helium—Figure 1 shows how helium mass spectrometer leak testing proceeds. The part is pressurized with helium and the chamber is evacuated down to less than 0.1 mbar absolute to eliminate background effects. The presence of helium leaking into the chamber is then detected by the mass spectrometer.

Helium Mass Spectrometry Method of Leak Testing

Figure 1: Test item is pressurized with helium within a test chamber. The chmber is evacuated, drawing helium out of the leaking test item. Mass spectromter then samples the vacuum chamber.

Equipment costs, maintenance costs, extra time required to evacuate helium from test fixturing in between test cycles, and ever rising helium costs makes this method the method of last resort. Typical applications include: heating, ventilating, and air conditioning (HVAC) components; pace makers; aluminum wheels; and airbag components.

For these type applications where leaks of 10–4 sccs or less must be detected for product integrity or safety, helium has its well-deserved place in the repertoire of best-match leak test techniques to consider.

In the next part of this Leak Testing 101 series we will discuss miscellaneous other testing techniques including: hydrogen ultrasonic, bubble testing, and air under water.

If you would like specific questions on best practices for leak testing (and other testing topics) answered in future articles, please send me your questions at jhoffmann@intertechdevelopment.com.


Note:  The above article has been reproduced from an article written by the author for Quality Digest



Leak testing 101 – Part 3

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In parts one and two of this ongoing primer on leak testing, we discussed pressure-decay testing and differential pressure-decay testing, respectively. Although those leak-testing methods remain the most widely used, it is often because they are assumed to be the least expensive leak-testing method.

To recap: Pressure-decay transducers for leak testing are the least expensive leak-testing sensor technology, often making pressure-decay methods the least expensive route for a given accuracy. However, pressure-decay methods are the slowest methods for leak detection.

In the mass-flow method (see figure 1), a part is pressurized along with a reference volume, and the amount of air that flows into the part to replace a leakage flow is measured directly in standard cubic centimeters per minute (sccm). A number of error proofing techniques are also available to guarantee test system reliability.The alternative to pressure-decay test methods are leak-testing systems using mass-flow sensors, which can provide fast and accurate testing over a much wider range of leak/volume ratios and testing conditions at about the same cost as differential pressure systems.

Mass Flow Method of Air Leak Testing

Figure 1: The key difference between this and the differential pressure method is that the mass-flow transducer reads the flow of air moving from the reference volume into the leak test item. The result is a direct reading of the leakage rate.

Mass-flow sensors are most often temperature-sensitive resistors that measure the temperature of incoming and outgoing flow as leakage flow is directed across a heated element, thereby transferring some heat to the flowing gas. If there is no leak, resistors are exposed to the same temperature. If there is an imbalance between resistors’ temperatures, a voltage is generated that is proportional to the mass flow. In this way there is a one-step direct measurement of the leakage rate.

InterTech’s mass-flow sensors have the capability to accurately detect and measure leaks as low as 0.01 sccm. This permits their use in applications that were previously believed to be beyond the capability of production leak detectors.

To this day, many mistakenly use much more expensive helium leak-testing methods because they do not appreciate that state-of-the-art mass-flow leak detectors can achieve required accuracies. Indeed, there are many antiquated mass-flow leak detectors that one can still find in the marketplace, identifiable by their use of mass-flow sensor technology that is slow, costly, and in many cases not suited for use in production leak testing. This has especially been true in applications involving low flows when leak detectors using transducers developed for the semiconductor industry are selected.

Modern mass-flow leak testing technology uses sensor designs that are not susceptible to clogging and are ideally suited for a wide range of industrial leak-testing applications. For example, InterTech Development Co.’s multi-channel touch screen mass-flow leak detectors achieve 0.01 sccm accuracy in leak measurements using patented mass-flow transducers that provide direct measurement of leakage with NIST traceable calibration.

Calibration and compensation for temperature and creepage effects are readily accomplished in systems using mass-flow detection, further extending their range of applications.

One can determine if the mass-flow leak sensing systems (e.g., leak detector, fixtures, software, systems integration) are state of the art and capable of achieving the 0.01 sccm standards by reviewing the following checklist:

• Is the mass-flow sensor designed for rapid cycle accurate leak testing?

• Is gauge repeatability and reproducibility (R&R) of the entire leak-test system in the industrial environment stipulated—not simply the gauge R&R of the leak detectors, which is only one component of overall performance?

• What temperature variations will the system handle?

• Does the mass-flow leak detector enhance performance with features such as: auto zero; test part temperature compensation; rapid and easy interchange of test sequences, providing ability to customize and recustomize leak testing for various products without any production delays; real-time display of all test stages and results, and data storage in buffer of test records; and tight integration of control software with mass-flow transducers and other system components?

 In summary, mass-flow sensors need to be specifically tailored to the leak testing requirements of a given application. Testing also requires automatic temperature compensation to ensure accuracy. When these requirements are met, mass-flow testing can detect leaks as small as 0.01 sccm. The larger the part volume, the better mass-flow test methods are when compared to pressure-decay leak testing methods.

However, there remain many critical leak-testing applications where mass-flow leak testing methods do not deliver the required sensitivity. In Part 4 of this series, we will discuss helium mass spectrometer leak testing that is required for many stringent leak-testing applications.

Note:  The above article has been reproduced from an article written by the author for Quality Digest