Diagnosing Failed Fuel Injectors
A fuel injector that failed and its pintle can no longer move can be identified using a mechanic’s stethoscope or just by touching it with a screwdriver. But this is a rather outdated method that is not suitable for detecting problems in today’s high-performance gasoline and diesel fuel-injected engines. A mechanic’s stethoscope, a screwdriver, or even the pistol-shaped injector tester with a blinking LED that some mechanics use can only detect that an injector has failed completely and its pintle no longer moves.
Today’s high-performance engines need an injector monitoring and testing method that can do more than just detecting that an injector is ‘dead’. There is a need for a method that can determine accurately how well is an injector working. An accurate diagnosis should be able to determine that an injector is as good as new, or that it is moderately worn and no longer meets its specifications, or that it is severely worn and well on its way toward a complete failure, or that it is ‘dead’. Additionally, such an injector monitoring method should be able to determine the condition of an injector in a numerically accurate and repeatable fashion.
Furthermore, stethoscopes, screwdrivers and blinking-LED testers cannot be used in most modern engines because the injectors are hidden under engine components and are not accessible (see for example the engine in Figure 1).
Monitoring Injectors Using Stress Waves
mhTechnosys developed and patented an injector monitoring and testing method that is free of all the limitations of previous methods and instruments. Our injector monitoring instrument generates a numerically accurate and repeatable condition index for a tested injector and it can test injectors that are hidden from view and inaccessible.
The sensor we use does not have to contact an injector to test it – it measures stress waves that travel from the tested injector to the sensor through engine components or along waveguides. The sensor can be several feet away from a tested injector.
Diagnosing injectors in an engine is fast and simple with our instrument. When a customer complains that his car engine is running roughly, or when the OBD II system reports “Cylinder X Misfire Detected”, it would take a mechanic less than five minutes to determine if an injector is the cause – less than it would take him to determine if a spark plug is the cause.
The monitoring method is based on measuring stress waves generated by pintle impacts when an injector valve opens and closes. The instrument consists of a sensor and a processing/display unit, as shown schematically in Figure 1. The sensor inspects all the injectors while temporarily attached to one location in the engine compartment. The processing/display unit can be a PC or a custom hand-held device. Alternatively, a monitoring functionality based on our technology can be a permanent addition to an engine and be used by the ECM and/or by the OBD system in real time.
Figure 1: Fuel Injector Testing Instrument (a sensor placed at one location tests all the injectors in an engine)
A test cycle consists of the instrument first acquiring the stress wave signature of one, several or all the injectors in an engine. It then automatically measures the pintle impact stress-wave intensities generated when the injector valves open and close, and the opening time of the valves. Figure 2 shows the results of such analysis for one injector. The opening and closing impact intensities are P1 and P2, respectively, and T is the valve opening time.
Figure 2: Analysis of Stress Wave Intensity Signature of an Injector
The diagnosis of injectors is based either on comparing the values of P1, P2 and T to tabulated standards, or on a comparison of these values between the injectors in an engine. Figure 3 shows the stress wave intensities of all four injectors in an engine that was idling roughly. The detection of a failing injector in cylinder No. 4 was instantaneous.
Figure 3: Test Results of Injectors in a Four-Cylinder Engine with Damaged Injector No. 4
mhTechnosys believes that vehicle and fuel delivery system manufacturers can benefit from this monitoring technology by offering customers fuel delivery systems that can be monitored for the same price as competitors’ offerings that cannot be monitored. Our US and German patents can protect this technological and marketing advantage for many years to come.
mhTechnosys is ready to demonstrate this injector monitoring technology to marketing, product development and engineering staff in the automotive industry. We have a presentation that explains the method and the instrument, a desktop demo system, and an in-car demo. Since the hardware and the software that comprise our monitoring instrument are tested and ready for industrial use, our invention can be made into a marketable product in several months.
Please read our Stress Waves Explained page for further information on the use of stress waves for monitoring and refer to our US patent and German patent for further technical details and various embodiments of our injector monitoring method.
For further information, please email us at info@mhtechnosys.com or call us at (410) 428-4806.