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Off-Car Fuel Injector ServicePosted 9/15/1998By Jim Linder
In the June "Tech to Tech" article, I covered the many aspects of on-car fuel injection service. This "service" in many cases may restore the fuel injectors to a proper operational condition, but there are times when this service simply isn't practical (like in the case of a total engine overhaul and the engine is apart) or just won't fix the problem (such as an extremely difficult restriction or carbon buildup). This month's article addresses aspects of off-car fuel injector service and the three major suppliers of off-car service equipment. In our fuel injector service business, we use all three of these products and each has its own spot in our shop. Our advice for anyone considering this type of service is to look at all three and then (and only then) decide what is good for your particular workplace, based on cost and need.
Fuel Injector Service Off Car Step one in any injector service is a thorough visual inspection and degreasing or cleaning. Cleaning and degreasing starts out with an air-powered agitated bath of "Simple Green" and water. This removes the external grease and oils from the injectors and prevents contamination of the cleaning tanks, etc. Fuel injectors that have painted surfaces with loose paint are glass-beaded to prevent contamination and repainted during a final stage. From this point onward, we will assume that each example includes a clean, externally good fuel injector.
Pattern Failure Units
Pattern failure units are tested according to their particular pattern failure. For example, Multecs are load tested many times and Ford units are cycled on flow to verify exact flow and repeat performance. Using the ASNU, New Age and Global Diagnostics units, the injectors are actually cleaned two different ways. ASNU and New Age both use an ultrasonic cleaning bath, with the Global unit using a straight-through flow method of cleaning with a solution. The exact methods and details of cleaning and case studies of actual vehicles will be explored next. Its combination unit cleans and flow tests the injectors using the same setup, from start to finish. The unit also includes a printout of each action the unit takes with each injector, measuring not only the flow, but also the loaded current the injector used during the test. This unit makes comparison testing very easy to do as the operator tests all injectors before cleaning and is provided with an actual printout of each injector's current draw and flow before and after the cleaning cycle. Injectors cleaned for this test case study were from an area shop that had cleaned a set of Buick 3.8 Liter V6 injectors with an on-car process that provided little or no results. ECM (electronic control module) block learn numbers were in the 140-150 range and all diagnostics showed a "lean" engine, with all other components looking good. Injectors were removed from the engine, degreased and flow tested in Global's unit. A printout of the flow test results is shown in Figure 2. Injectors were somewhat uneven and a few mils (millimeters) on the low side. Units were given a clean cycle on the Global unit (an 8-minute flow cycle with the Global solvent from the machine) and retested for current and flow. Results are seen in Figure 3.
Note on the printouts: Not only is flow measured, but the loaded current of each injector is also included. This is a most valuable tool with the pattern shorted coil Multec injectors! Injectors were then flowing much higher than before and exhibited an even flow rate. Injector upper filters, o-rings and seals were replaced at this time (another advantage of off-car service). Injectors were reinstalled, the ECM was relearned and the vehicle was test-driven for results - idle was much smoother and integrator, block learn numbers were in their proper ranges.
ASNU Fuel Injection Service Equipment 
As shown, injectors were in very bad shape based on a visual inspection, with broken end caps and rusty external bodies. However, all injector lower pintles were OK and injectors were glass-beaded (to prevent chemical contamination) and checked for operation with pulser to confirm opening.
After external cleaning and pulse operation, injectors were placed on the ASNU flow rack and flowed to confirm operation. Results were terrible! Injectors flowed 0, 10, 24, 0, 23 and 10 mils - not good considering the factory specification is 50 mils each!
Injectors were then placed in the ASNU ultrasonic cleaning tank. The ASNU unit ultrasonically cleans each injector with the chemicals and ultrasonic waves at different frequencies, and also pulses each injector, causing a reverse flush from bottom to top to occur. Note the material coming out the top of each injector in the bath with filters removed. Knowing how bad these injectors were, we ran the injector through three different cycles (allowing the injectors to heat up and using different ultrasonic frequencies). Injectors were then removed from the cleaning tank and retested. Each injector tested right on the factory specification of 50 mils. Note: This is a great case study for off-car cleaning, as the entire cost to recondition the six injectors was much less than the cost of one new replacement injector!
Intake plenum was removed for current load testing of all injectors. One injector was shorted with a very low resistance of approximately 3 ohms. Upon further testing, one other injector was testing marginal under a stress load bench while observing the current waveform. Two good core injectors were tested for load and all injectors were cleaned in the New Age ultrasonic tank. The New Age approach is to clean the injectors ultrasonically with the injector held open with a slight current from harness, and then a reverse flow adapter is used to clean out injectors and remove the fluids prior to flow testing. Using a matched set of six, the injectors' new filters and o-rings were installed prior to injector replacement in the vehicle. This was a fairly straightforward repair on a "pattern failure" vehicle equipped with the GM Multec fuel injector. The off-car service unit provided by New Age made the repair very quick, and the overall cost was again far less to the customer than new replacement units would have been.
Our second case study with the New Age unit included another piece of test equipment, Mac Tools' Scanalizer. This latest unit from the Hickok folks uses state-of-the-art hookups and technology to perform an 11-step fuel system test. Test selections include:
Our test vehicle was a 1992 Buick Regal equipped with the 3800 V6 engine. The customer complained of a slight tip in chuggle or misfire at approximately 45-48 mph with light throttle and torque converter in. A road test confirmed the problem with a block learn slightly higher than usual at 140 counts. As all other possibilities had been looked at by the customer and the repair shop, we hooked up the Scanalizer as shown in the pictures above.
The new age unit shows approximately 5 mils difference in the flow rate per fuel injector. Injectors were cleaned in an ultrasonic tank for an 8-10 minute cycle, and retested. All units now flowed correctly at 50 mils and were reinstalled in the vehicle. The PCM was relearned and the vehicle was test driven with no signs of a tip in chuggle or misfire as before!
Service Options The vehicle case studies included in this article were performed at our Indianapolis service and technician training center over a couple of weeks, and all customers (in this case local repair shops) were very happy with the services provided.
If these services are not available in your area, feel free to call us at (317) 487-9460, or stop in at our Web page (http://www.lindertech.com).
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Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
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Global Diagnostics
New Age Four
The Scanalizer hooks up directly to the PCM connector (under the hood on this vehicle) and the fuel rail, and performs 11 fuel system tests using the PCM connector as a control center for testing! Fuel pump pressure, leak down, regulator setting, and a full dynamic test of each fuel injector's flow and magnetic inductance rate are performed in just a few minutes. Flow rate is measured in grams per second and inductance is measured as a percentage for comparison to each other. This vehicle shows a very uneven flow rate per injector, and injectors were removed for an injector off-car service.
