For 1990-2009 cars

### 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

#### Fuel Injector Balance Test Example

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 is first used to energize the fuel pump relay. The fuel injector tester 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.

### Diagnostic Aids

• | Monitoring the Cylinder 1-6 Current Misfire 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

#### Schematic Reference

Engine Controls Schematics

#### Scan Tool Reference

Control Module References for scan tool information

#### Special Tools Required

• | CH 48027 Digital Pressure Gage

• | J 39021 Fuel Injector Coil and Balance Tester

• | J39021-210 Injector Selector Switch Box

• | EL 39021-460 Fuel Injector Test Adapter

• | J 44602 Fuel Injector Test Adapter

• | For equivalent regional tools, refer to Special Tools.

### Component Testing

1. Ignition ON, verify that the engine coolant temperature (ECT) is less than 94°C (201°F) with a scan tool.

⇒ | If the ECT is greater than 94°C (201°F) allow the engine to cool before proceeding.

2. Ignition OFF, install the fuel pressure gage.
3. Ignition ON, verify the fuel pressure is within 380-410 kPa (55-60 psi).

⇒ | If the fuel pressure is not within the specified range, refer to Fuel System Diagnosis for further diagnosis of the fuel system.

4. Monitor the fuel pressure gage for 1 minute. Verify that the fuel pressure does not drop more than 34 kPa (5 psi).

⇒ | If the fuel pressure decreases more than 34 kPa (5 psi) refer to Fuel System Diagnosis for further diagnosis of the fuel system.

Caution: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding.

5. Connect the J 39021 Fuel Injector Coil and Balance Tester , J39021-210 Injector Selector Switch Box , and EL 39021-460 Fuel Injector Test Adapter to the muti-way connector X????? of the Q17 fuel injectors, with the amperage supply selector switch set to the 0.5-2.5 amp position. If the upper intake manifold has been removed, use J 44602 Fuel Injector Test Adapter in place of J39021-210 Injector Selector Switch Box and EL 39021-460 Fuel Injector Test Adapter , and connect directly to a fuel injector.
6. Command the Fuel Pump Relay ON with a scan tool and record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the first pressure reading.

Note:

• | 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.

7. Energize the fuel injector by depressing the Push to Start Test button on the fuel injector tester. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the second pressure reading.
8. 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 difference between any individual pressure drop and the average pressure drop is more than 20 kPa (3 psi), replace the Q17 fuel injector.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Injector Replacement