| Table 1: | Injector Balance Test Example |
System Description
The scan tool is first used to energize the fuel pump relay. The scan tool is then used to pulse each injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.
Cylinder | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
1st Reading | 365 kPa (53 psi) | 365 kPa (53 psi) | 365 kPa (53 psi) | 365 kPa (53 psi) | 365 kPa (53 psi) | 365 kPa (53 psi) |
2nd Reading | 245 kPa (36 psi) | 200 kPa (30 psi) | 245 kPa (36 psi) | 240 kPa (35 psi) | 245 kPa (36 psi) | 255 kPa (37 psi) |
Amount of Drop | 120 kPa (17 psi) | 165 kPa (23 psi) | 120 kPa (17 psi) | 125 kPa (18 psi) | 120 kPa (17 psi) | 110 kPa (16 psi) |
Average Range: 117-137 kPa (16.5-19.5 psi) | Injector OK | Faulty injector - too much fuel drop | Injector OK | Injector OK | Injector OK | Faulty injector - too little fuel drop |
Test Description
The number below refers to the step number on the diagnostic table.
-
The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
-
The engine coolant temperature must be less than the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
-
This step checks that the fuel pressure is within the specified operating range of this fuel system.
-
This step checks for a steady fuel pressure reading. A steady fuel pressure reading indicates that the fuel system is operating properly.
-
The fuel injectors are flowing properly if the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. Refer to the examples in the preceding table.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
2 | Did you perform the Fuel Injector Coil Test? | -- | Go to Step 3 | |||||
|
Important : DO NOT perform this test if the engine coolant temperature (ECT) is above 94°C (201°F). Observe the ECT Sensor parameter with a scan tool. Is the ECT Sensor parameter less than the specified value? | 94°C (201°F) | Go to Step 5 | Go to Step 4 | |||||
Allow the engine to cool to less than the specified value. Is the engine coolant temperature less than the specified value? | 94°C (201°F) | Go to Step 5 | -- | |||||
|
Important: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.
Important:
Is the fuel pressure within the specified value? | 330-382 kPa (48-56 psi) | Go to Step 6 | Go to Fuel System Diagnosis | |||||
Monitor the fuel pressure gage for 1 minute. Does the fuel pressure decrease by more than the specified value? | 34 kPa (5 psi) | Go to Fuel System Diagnosis | Go to Step 7 | |||||
|
Notice: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding.
Important: Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Is the difference between any individual pressure drop and the average pressure drop more than the specified value? | 10 kPa (1.5 psi) | Go to Step 8 | ||||||
8 | Replace the affected fuel injectors. Did you complete the replacement? | -- | Go to Step 9 | -- | ||||
9 |
Does an engine performance concern still exist? | -- | System OK |
