Table 1: | Fuel Injector Balance Test Example (Typical) |
The scan tool is first used to energize the fuel pump. 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 the flow through each injector.
Cylinder | 1 | 2 | 3 | 4 |
---|---|---|---|---|
1st Reading | 296 kPa (43 psi) | 296 kPa (43 psi) | 296 kPa (43 psi) | 296 kPa (43 psi) |
2nd Reading | 131 kPa (19 psi) | 117 kPa (17 psi) | 124 kPa (18 psi) | 145 kPa (21 psi) |
Amount of Drop | 165 kPa (24 psi) | 179 kPa (26 psi) | 172 kPa (25 psi) | 151 kPa (22 psi) |
Average Range: 156-176 kPa (22.5-25.5 psi) | Injector OK | Replace fuel injector - too much fuel pressure drop | Injector OK | Replace fuel injector - too little fuel pressure drop |
The numbers below refer to the step numbers on the diagnostic table.
The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
The fuel pressure should be within the specified range. Refer to Fuel System Diagnosis if the fuel pressure is not within the specified range.
The fuel pressure should reach a steady value. Refer to Fuel System Diagnosis if the fuel pressure does not stabilize.
If the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value, the fuel injectors are flowing properly. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading.
Step | Action | Values | Yes | No | ||||
---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 | Did you perform the Fuel Injector Coil Test? | -- | Go to Step 3 | |||||
Important : Do not perform this test if the engine coolant temperature 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 4 | -- | |||||
Important: Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic.
Important:
Is the fuel pressure within the specified value? | 284-325 kPa (41-47 psi) | Go to Step 5 | Go to Fuel System Diagnosis | |||||
Important: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute. Does the fuel pressure drop more than the specified value? | 34 kPa (5 psi) | Go to Fuel System Diagnosis | Go to Step 6 | |||||
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. 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? | 10 kPa (1.5 psi) | Go to Step 7 | ||||||
7 | Replace the affected fuel injector. Refer to Fuel Injector Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- | ||||
8 | Operate the vehicle in order to verify the repair. Does a driveability condition still exist? | -- | System OK |