A new essential CH-47976 Active Fuel Injector Tester (AFIT) has been released by SPX Kent-Moore (fig. 1). Shipment of this tool begins in June and is being rolled out initially to all Cadillac dealers (US and Canada), Tier 1 and 2 Chevrolet and GMC dealers in the US, and high volume Chevrolet and GMC dealers in Canada. The AFIT will be an available tool for all other dealers at essential pricing. 
WHY A NEW TESTER WAS DEVELOPED
The AFIT was developed to address important issues concerning diagnosing today's gasoline fuel injection systems --
- Improve the accuracy of diagnostics for the new AFIM (Air Fuel Imbalance Monitor) system due to increasing emission requirements. Codes P1174 and P1175 are new for AFIM diagnostics.
- Tech 2 output control for the Fuel Injector Balance Test does not work on vehicles equipped with Theft Immobilizer system (see Diagnosing Fuel Injectors with Tech 2 below).
Existing SI procedures using a pressure gauge and Tech 2 are not reliable enough to determine the root cause of certain driveabilty issues. Needless replacement of injectors can occur if not diagnosed correctly.
TIP:Â The AFIT can perform multiple fuel system tests, including the Fuel Injector Coil Test, Fuel Pump Pressure Leakdown Test, and the Fuel Injector Balance Test.
TIP:Â 2004-06 Cacillac SRX and XLR, and 2006 Cadillac STS with LH2 engine require the DLC cable and an additional injector harness connector supplied with the AFIT. The Tech 2 is not able to initiate an Injector Balance Test on these vehicles.
TIP:Â On vehicles with Theft Immobilizer system and the LH2 vehicles listed above, the AFIT prompts the user to install a fuel injector harness adapter.
HOW THE AFIT WORKS
The CH-47976 Active Fuel Injector Tester (AFIT) is a necessary diagnostic component for today's gasoline fuel injector technology (fig. 2). This new device uses a microprocessor and software program to completely automate the test procedure. It eliminates variations in test results due to individual testing methods or physical property changes of the fuel.Â
AÂ Main Control Unit
BÂ Fuel Management Unit
CÂ DLC Adapter
All measurements and calculations are performed by the AFIT software, which eliminates the possibility of human error.
The AFIT connects to the DLC with a cable. Certain applications with the Theft Immobilizer system or LH2 engine mentioned above also require the supplied adapter harness. These harnesses connect directly to the injectors or to the vehicle injector harness connector
The AFIT is equipped with a reference injector with a known standard flow rate. This reference injector is used to monitor changes within the fuel system during the balance test. Dynamic changes in fuel properties can occur during the test when cold fuel from the fuel tank enters a hot fuel rail. This can cause the pressure drop measurements to fluctuate from one injector to the other. The AFIT software compensates for these fluctuations by using the reference injector flow measurement within the calculations to determine the vehicle's injector flow rate. To ensure a fixed reference point for the test, the pressure drop for the reference injector is measured three times for each vehicle injector tested.
The AFIT will determine if the injectors are within the GM design and operating specifications for each specific engine. Each injector is identified as GOOD or BAD, using the balance graph. When the test results are downloaded to the TechLine PC, a red bar on the balance graph identifies a suspect injector, a green bar identifies a good injector.
COMPARISON of PRESSURE DROP MEASUREMENT vs. AFIT TIME MEASUREMENT
Current Pressure Drop Measurement Using Tech 2Â (fig. 3)
Â
- Measurement is based on starting and ending fuel rail pressures
- Fuel pressure gauge must be recorded manually
- Dynamic fuel properties during the test may affect readings
- Consistent timing of each step in the procedure is difficult to maintain across all of the injectors. This can lead to differences in the conditions under which each injector was tested, resulting in an overall poor technical test.
- Fuel injector flow properties are determined indirectly through the fuel pressure drop of each injector.
AFIT Time Measurement (fig. 4)Â
- The amount of time it takes for the fuel pressure to sweep through the 90% - 60% of available fuel pressure is measured. This is the window in which fuel injectors operate most of the time.
- The injectors are all tested and compared at the same pressure points and the timing of each step in the process is consistent.
- All measurements are captured digitally, and the sequence is fully automated.
- Time measurement strategy is a better indication of the injector flow properties.
- The AFIT user interface is easier to operate.
USING THE AFIT
The AFIT accurately determines if the fuel system is the cause of a condition. If test results show injector clogging, injectors are to be cleaned or replaced. Refer to SI for the proper cleaning or relacement proceure for the vehicle you are working on. Run the test again to verify that the cleaning or replacement has been successful. A comparison of the before and after test results can be used to document that the repair was successful.
TIP:Â Not all injectors can be cleaned. Refer to SI or GM Bulletin 03-06-04-030A to determine which injectors can be cleaned.
During the re-test, the AFIT again pinpoints any faulty injector(s) that were not improved. If cleaning was performed, these injector(s) will now need to be replaced. If all of the injectors now test good, the condition has likely been repaired. It is recommended that the vehicle be operated to fully verify the repair.
Complete test results, including balance percentages and flow rates, can be downloaded to the Techline PC for printing and attachment to the repair order for repair verification purposes.
- Thanks to Russ Dobson, Kevin Suhajda and Brian Echtinaw
WHY A NEW TESTER WAS DEVELOPED
The AFIT was developed to address important issues concerning diagnosing today's gasoline fuel injection systems --
- Improve the accuracy of diagnostics for the new AFIM (Air Fuel Imbalance Monitor) system due to increasing emission requirements. Codes P1174 and P1175 are new for AFIM diagnostics.
- Tech 2 output control for the Fuel Injector Balance Test does not work on vehicles equipped with Theft Immobilizer system (see Diagnosing Fuel Injectors with Tech 2 below).
Existing SI procedures using a pressure gauge and Tech 2 are not reliable enough to determine the root cause of certain driveabilty issues. Needless replacement of injectors can occur if not diagnosed correctly.
TIP:Â The AFIT can perform multiple fuel system tests, including the Fuel Injector Coil Test, Fuel Pump Pressure Leakdown Test, and the Fuel Injector Balance Test.
TIP:Â 2004-06 Cacillac SRX and XLR, and 2006 Cadillac STS with LH2 engine require the DLC cable and an additional injector harness connector supplied with the AFIT. The Tech 2 is not able to initiate an Injector Balance Test on these vehicles.
TIP:Â On vehicles with Theft Immobilizer system and the LH2 vehicles listed above, the AFIT prompts the user to install a fuel injector harness adapter.
HOW THE AFIT WORKS
The CH-47976 Active Fuel Injector Tester (AFIT) is a necessary diagnostic component for today's gasoline fuel injector technology (fig. 2). This new device uses a microprocessor and software program to completely automate the test procedure. It eliminates variations in test results due to individual testing methods or physical property changes of the fuel.Â
AÂ Main Control Unit
BÂ Fuel Management Unit
CÂ DLC Adapter
All measurements and calculations are performed by the AFIT software, which eliminates the possibility of human error.
The AFIT connects to the DLC with a cable. Certain applications with the Theft Immobilizer system or LH2 engine mentioned above also require the supplied adapter harness. These harnesses connect directly to the injectors or to the vehicle injector harness connector
The AFIT is equipped with a reference injector with a known standard flow rate. This reference injector is used to monitor changes within the fuel system during the balance test. Dynamic changes in fuel properties can occur during the test when cold fuel from the fuel tank enters a hot fuel rail. This can cause the pressure drop measurements to fluctuate from one injector to the other. The AFIT software compensates for these fluctuations by using the reference injector flow measurement within the calculations to determine the vehicle's injector flow rate. To ensure a fixed reference point for the test, the pressure drop for the reference injector is measured three times for each vehicle injector tested.
The AFIT will determine if the injectors are within the GM design and operating specifications for each specific engine. Each injector is identified as GOOD or BAD, using the balance graph. When the test results are downloaded to the TechLine PC, a red bar on the balance graph identifies a suspect injector, a green bar identifies a good injector.
COMPARISON of PRESSURE DROP MEASUREMENT vs. AFIT TIME MEASUREMENT
Current Pressure Drop Measurement Using Tech 2Â (fig. 3)
 - Measurement is based on starting and ending fuel rail pressures
- Fuel pressure gauge must be recorded manually
- Dynamic fuel properties during the test may affect readings
- Consistent timing of each step in the procedure is difficult to maintain across all of the injectors. This can lead to differences in the conditions under which each injector was tested, resulting in an overall poor technical test.
- Fuel injector flow properties are determined indirectly through the fuel pressure drop of each injector.
AFIT Time Measurement (fig. 4)Â
- The amount of time it takes for the fuel pressure to sweep through the 90% - 60% of available fuel pressure is measured. This is the window in which fuel injectors operate most of the time.
- The injectors are all tested and compared at the same pressure points and the timing of each step in the process is consistent.
- All measurements are captured digitally, and the sequence is fully automated.
- Time measurement strategy is a better indication of the injector flow properties.
- The AFIT user interface is easier to operate.
USING THE AFIT
The AFIT accurately determines if the fuel system is the cause of a condition. If test results show injector clogging, injectors are to be cleaned or replaced. Refer to SI for the proper cleaning or relacement proceure for the vehicle you are working on. Run the test again to verify that the cleaning or replacement has been successful. A comparison of the before and after test results can be used to document that the repair was successful.
TIP:Â Not all injectors can be cleaned. Refer to SI or GM Bulletin 03-06-04-030A to determine which injectors can be cleaned.
During the re-test, the AFIT again pinpoints any faulty injector(s) that were not improved. If cleaning was performed, these injector(s) will now need to be replaced. If all of the injectors now test good, the condition has likely been repaired. It is recommended that the vehicle be operated to fully verify the repair.
Complete test results, including balance percentages and flow rates, can be downloaded to the Techline PC for printing and attachment to the repair order for repair verification purposes.
- Thanks to Russ Dobson, Kevin Suhajda and Brian Echtinaw
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