Injector Balance Test
Test Description
Number(s) below refer to the step number(s) in the Diagnostic Test:
2. Relieve the fuel pressure by connecting the J 34730-1 Fuel Pressure Gauge to the fuel pressure connection on the fuel rail.
WARNING: In order to reduce the risk of fire and personal injury, wrap a shop towel around the fuel pressure connection. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gauge. Place the towel in an approved container when the connection of the fuel pressure gauge is complete.
Place the fuel pressure gauge bleed hose in an approved gasoline container. With the ignition switch "OFF", open the valve on the fuel pressure gauge.
3. Record the lowest voltage displayed by the Digital Volt Meter (DVM) after the first second of the test. (During the first second, voltage displayed by the DVM may be inaccurate due to the initial current surge.)
Injector Specifications:
Resistance Ohms: 11.8 - 12.6
Voltage Specification at 10°C - 35°C (50°F - 95°F): 5.7 - 6.6
- The voltage displayed by the DVM should be within the specified range.
- The voltage displayed by the DVM may increase throughout the test as the fuel injector windings warm and the resistance of the fuel injector windings changes.
- An erratic voltage reading (large fluctuations in voltage that do not stabilize) indicates an intermittent connection within the fuel injector.
5. Injector Specifications:
Highest Acceptable Voltage Acceptable Reading Above/Below 35°C/10°C (95°F/50°F): 9.5 Volts.
Acceptable Subtracted Value: 0.6 Volts.
7. The Fuel Injector Balance Test portion of this test (Step 7 through Step 11) checks the mechanical (fuel delivery) portion of the fuel injector. An Engine cool down period of 10 minutes is necessary in order to avoid irregular fuel pressure readings due to "Hot Soak" fuel boiling.
- Injector Coil test procedure (steps 1-6) and Injector Balance test procedure (steps 7-11).
Diagnostic Test
1. Was the "On-Board Diagnostic (OBD) System Check" performed?
[YES] Go to Step 2.
[NO] Go to OBD System Check. Description of On-Board Diagnostics
2. a. Turn the Engine "OFF".
CAUTION: In order to prevent flooding of a single cylinder and possible Engine damage, relieve the fuel pressure before performing the fuel injector coil test procedure.
b. Relieve the fuel pressure. Refer to Test Description Number 2.
c. Connect the J 39021-5V Fuel Injector Tester to B+ and ground, and to the J39021-90 Injector Switch Box.
d. Connect the injector switch box to the grey fuel injector harness connector located at the front of the EVAP canister bracket.
e. Set the amperage supply selector switch on the fuel injector tester to the "Coil Test" 0.5 amp position.
f. Connect the leads from the J 39200 Digital Voltmeter (DVM) to the fuel injector tester. Refer to the illustrations associated with the test description.
g. Set the DVM to the tenths scale (0.0).
h. Observe the Engine coolant temperature.
i. Is the Engine coolant temperature within the specified to values?
[VALUES] 10°C (50°F) to 35°C (95°F)
[YES] Go to Step 3.
[NO] Go to Step 5.
3. a. Set the injector switch box to injector # 1.
b. Press the "Push to Start Test" button on the fuel injector tester.
c. Observe the voltage reading on the DVM.
NOTE: The voltage reading may rise during the test.
d. Record the lowest voltage observed after the first second of the test.
e. Set the injector switch box to the next injector and repeat steps 2, 3, and 4.
f. Did any fuel injector have an erratic voltage reading (large fluctuations in voltage that did not stabilize) or a voltage reading outside of the specified values?
[VALUES] 5.7 - 6.6 V.
[YES] Go to Step 4.
[NO] Go to Step 7.
4. a. Replace the faulty fuel injector(s).
b. Is the action complete?
[YES] Go to Step 7.
5. a. Set the injector switch box to injector # 1.
b. Press the "Push to Start Test" button on the fuel injector tester.
c. Observe the voltage reading on the DVM.
NOTE: The voltage reading may rise during the test.
d. Record the lowest voltage observed after the first second of the test.
e. Set the injector switch box to the next injector and repeat steps 2, 3, and 4.
f. Did any fuel injector have an erratic voltage reading (large fluctuations in voltage that did not stabilize) or a voltage reading above the specified value?
[VALUES] 9.5 V.
[YES] Go to Step 4.
[NO] Go to Step 6.
6. a. Identify the highest voltage reading recorded (other than those above 9.5 V).
b. Subtract the voltage reading of each injector from the highest voltage selected in step 1. Repeat until you have a subtracted value for each injector.
c. For any injector, is the subtracted value in step 2 greater than the specified value?
[VALUES] 0.6 V.
[YES] Go to Step 4.
[NO] Go to Step 7.
7. a. Connect the J 34730-1 Fuel Pressure Gauge to the fuel pressure test port.
WARNING: In order to reduce the risk of fire and personal injury, wrap a shop towel around the fuel pressure connection. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gauge. Place the towel in an approved container when the connection of the fuel pressure gauge is complete.
b. Energize the fuel pump using the Scan Tool.
c. Place the bleed hose of the fuel pressure gauge into an approved gasoline container.
d. Bleed the air out of the fuel pressure gauge.
e. With the fuel pump running, observe the reading on the fuel pressure gauge.
f. Is the fuel pressure within the specified values?
[VALUES] 296 kPa - 376 kPa (43 - 55 psi).
[YES] Go to Step 8.
[NO] Go to Fuel System Diagnosis. Fuel System Diagnosis
8. a. Turn the fuel pump "OFF".
b. Does the fuel pressure remain constant?
[YES] Go to Step 9.
[NO] Go to Fuel System Diagnosis. Fuel System Diagnosis
9. a. Connect the J 39021-5V Fuel Injector Tester and J39021-90 Injector Switch Box to the fuel injector harness connector.
b. Set the amperage supply selector switch on the fuel injector tester to the "Balance Test" 0.5 - 2.5 amp position.
c. Using the Scan Tool turn the fuel pump "ON" then "OFF" in order to pressurize the fuel system.
d. Record the fuel pressure indicated by the fuel pressure gauge after the fuel pressure stabilizes. This is the first pressure reading.
f. Energize the fuel injector by depressing the "Push to Start Test" button on the fuel injector tester.
g. Record the fuel pressure indicated by the fuel pressure gauge after the fuel pressure gauge needle has stopped moving. This is the second pressure reading.
h. Repeat steps 1 through 6 for each fuel injector.
i. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value.
j. Obtain a pressure drop value for each fuel injector.
k. Add all of the individual pressure drop values. This is the total pressure drop.
l. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop.
m. Does any fuel injector have a pressure drop value that is either higher than the average pressure drop or lower than the average pressure drop by the specified value?
[VALUES] 10 kPa (1.5 psi).
[YES] Go to Step 10.
[NO] Go to OBD System Check. Description of On-Board Diagnostics
10. a. Retest any fuel injector that does not meet the specification. Refer to the procedure in step 11.
NOTE: Do not repeat any portion of this test before running the Engine in order to prevent the Engine from flooding.
b. Does any fuel injector still have a pressure drop value that is either higher than the average pressure drop or lower than the average pressure drop by the specified value?
[VALUES] 10 kPa (1.5 psi).
[YES] Go to Step 11.
[NO] Go to Diagnosis by Symptom. Symptom Related Diagnostic Procedures
11. a. Replace the faulty fuel injector(s).
b. Is the action complete?
[YES] Verify repair.