Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Cylinder | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
First Reading | 360 kPa (52 psi) | 360 kPa (52 psi) | 360 kPa (52 psi) | 360 kPa (52 psi) | 360 kPa (52 psi) | 360 kPa (52 psi) |
Second Reading | 195 kPa (28 psi) | 138 kPa (20 psi) | 195 kPa (28 psi) | 195 kPa (28 psi) | 235 kPa (34 psi) | 195 kPa (28 psi) |
Amount Of Drop | 166 kPa (24 psi) | 222 kPa (32 psi) | 166 kPa (24 psi) | 166 kPa (24 psi) | 125 kPa (18 psi) | 166 kPa (24 psi) |
Average Range: 156-176 kPa (22.5-25.5 psi) | Injector OK | Fuel Injector - Too Much Pressure Drop | Injector OK | Injector OK | Faulty Injector - Too Little Pressure Drop | Injector OK |
Circuit/System Description
The scan tool first energizes the fuel pump and then the injectors 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.
Diagnostic Aids
| • | Monitoring the misfire current counters, or misfire graph, may help to isolate the fuel injector that is causing the condition. |
| • | Operating the vehicle over a wide temperature range may help isolate the fuel injector that is causing the condition. |
| • | Perform the fuel injector balance test within the conditions of the customers concern. A fuel injector condition may only be apparent at a certain temperature, or under certain conditions. |
Reference Information
Connector End View Reference
Scan Tool Reference
Special Tools Required
J 34730-1A Fuel Pressure Gage
Component Testing
Fuel Injector Balance Test with Special Tool
- Ignition ON, with a scan tool verify that the engine coolant temperature (ECT) is less than 94°C (201°F).
- Ignition OFF, install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal .
- Ignition ON, verify the fuel pressure is within 380-410 kPa (55-60 psi).
- Monitor the fuel pressure gage for 1 minute. Verify that the fuel pressure does not drop more than 34 kPa (5 psi).
- With a scan tool, select the Fuel Injector Balance Test function, within the Special Functions menu. Select a fuel injector to be tested and press Enter in order to prime the fuel system. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the 1st pressure reading.
- Energize the fuel injector by depressing the Pulse Injector button on the scan tool. This will energize the fuel injector and decrease the fuel pressure. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the 2nd pressure reading.
- Press Enter to return to the Select Injector screen.
- Add all of the individual pressure drop values in order to calculate the total pressure drop. Divide the total pressure drop by the number of fuel injectors in order to calculate the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be more than 20 kPa (3 psi).
| ⇒ | If the ECT is greater than 94°C (201°F) allow the engine to cool before proceeding. |
| ⇒ | If the fuel pressure is not within the specified range refer to Fuel System Diagnosis for further diagnosis of the fuel system. |
| ⇒ | If the fuel pressure decreases more than 34 kPa (5 psi) refer to Fuel System Diagnosis for further diagnosis of the fuel system. |
Notice: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding.
Important:
• Repeat this step for each fuel injector in order to obtain a pressure drop value for each fuel injector. • The fuel pressure may rise after the fuel injector stops pulsing. Record the fuel pressure value immediately after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value.
| ⇒ | If the difference between any individual pressure drop and the average pressure drop is more than 20 kPa (3 psi), replace the fuel injector. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
