Fuel Injector Diagnosis

Fuel Injector Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The fuel injectors are cooled by a calibrated amount of fuel flow through the injector body to the injector return lines. This is referred to as injector return flow leakage. Engine temperature, vehicle load and the fuel type used effect the amount of return flow through the injectors. If the injectors are worn, damaged or contaminated, the amount of fuel flowing through the injector body may increase, resulting in improper injector performance.

Reference Information
Schematic Reference

Engine Controls Schematics [1][2]Electrical Diagrams
Special Tools

* J 45873 Fuel Return Volume Test Kit
* J-45873-30 Injector Flow Test Adapter
* CH-50378 Injector Leakage Adaptor
* CH-50377-A Fuel Injector Return Line Plug

Diagnostic Aids

* Contaminated fuel or incorrect fuel may cause high fuel return flow.
* The fuel return volumes vary based on the American Petroleum Institute (API) rating of the diesel fuel.
* A fuel injector may have high fuel return flow only at higher engine temperatures.

Circuit/System Testing

Note:
* If you were not referred to this test from another diagnostic, do not perform this procedure.
* Only perform this test when the fuel temperature is warmer than 18°C (65°F).
* Measure and record the fuel return rates for each injector.

1. Install the CH-50378 and the CH-50377-A to any one of the fuel injectors.
2. Connect the yellow hose from the J 45873 to the J-45873-30 .
3. Connect the J-45873-30 with yellow hose to the fuel injector leakage adaptor and install the retaining clip.
4. Install the yellow hose in one of the J 45873 graduated cylinders.

Note: At may take several minutes to purge the air from the yellow hose.

5. Run the engine until fuel starts dripping into the graduated cylinder and yellow hose is full of fuel.
6. Elevate the yellow hose to retain the fuel in the hose, and empty the graduated cylinder into a suitable container. Return the yellow hose to the empty graduated cylinder.
7. Idle the engine for 1 minute.

Note: During replacement of the injectors, inspect the inlet and outlet fittings for corrosion or contamination. Refer to Contaminants-in-Fuel Diagnosis Contaminants-in-Fuel Diagnosis.

8. Measure and record the quantity of fuel in the graduated cylinder. Repeat this process for each fuel injector. Refer to Fuel System Specifications [1][2]Fuel Delivery and Air Induction for maximum single fuel injector return flow.

• If greater than the specified value, replace those fuel injectors that had high return flow and retest the fuel return flow, refer to Fuel System Specifications [1][2]Fuel Delivery and Air Induction. Replace any additional high return flow injectors and proceed to the next number step.

9. Install and connect all fuel system components that were previously removed or disconnected.
10. Start and idle the engine. You may have to prime the fuel system before the engine will start. Command the fuel pressure control to 120 MPa (17,400 psi) with a scan tool. The actual fuel pressure should be the same as the commanded pressure.

• If the engine does not start or the fuel pressure is less than 120 MPa (17,400 psi) when commanded, replace the G18 high pressure fuel pump.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests Diagnostic Repair Verification after completing the diagnostic procedure.

* Fuel Injection Pump Replacement Fuel Injection Pump Replacement
* Fuel Injector Replacement (Left Side) Fuel Injector Replacement (Left Side)Fuel Injector Replacement (Right Side) Fuel Injector Replacement (Right Side)
* Perform the Fuel Injector Flow Rate Programming Programming and Relearning procedure after replacement of a fuel injector.
* Perform the scan tool Diesel Particulate Filter (DPF) Regeneration Enable Diesel Particulate Filter (DPF) Regeneration Enable procedure if the scan tool DPF Soot Mass is less than 30 g. If the scan tool DPF Soot Mass is 30 g or greater, perform the Diesel Particulate Filter (DPF) Service Regeneration Diesel Particulate Filter (DPF) Service Regeneration procedure.