Fuel System Diagnosis - High Pressure Side

Fuel System Diagnosis - High Pressure Side

Diagnostic Instructions

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

Circuit/System Description

High Pressure System

The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn by the fuel supply pump from the primary fuel tank and delivered to the high-pressure pump. The pump is engine-driven by the camshaft gear. High pressure fuel is regulated by the fuel pressure regulator mounted on the fuel injection pump. From the high-pressure pump, the fuel moves to the left and right fuel rails through high pressure metal lines. Each fuel rail distributes high pressure fuel to one bank of 4 fuel injectors. The fuel pressure relief valve is located on the left rail, and relieves excessive fuel pressure which returns to the fuel tank.

Return System

The fuel return system routes fuel from the fuel injectors, the pressure relief valve, and the fuel injection pump. The return fuel travels to the fuel cooler and then to the fuel tank. This fuel is used to cool and lubricate the injection pump and the injectors.

Diagnostic Aids

- 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.
- Fuel that is contaminated with gasoline may cause permanent damage to the fuel pressure relief valve. Refer to Contaminants-in-Fuel Diagnosis Component Tests and General Diagnostics.
- Verify there are no aftermarket power enhancing devices installed.

Reference Information

Special Tools Required

- J 45873 Fuel Return Volume Test Kit
- J-45873-30 Injector Flow Test Adapter

Circuit/System Verification

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).

1. Start and idle the engine
- If engine does not start
Refer to Pressure Relief Valve Test -- No Start Component Tests and General Diagnostics.
- Engine starts and idles
2. Verify the Actual Fuel Rail Pressure is within 690 kPa (100 psi) of the Desired Fuel Rail Pressure.
- If the Actual Fuel Rail Pressure is not within 690 kPa (100 psi) of the Desired Fuel Rail Pressure.
Refer to Pressure Relief Valve Test -- Engine Running Component Tests and General Diagnostics.
- If Actual Fuel Rail Pressure is within 690 kPa (100 psi) of the Desired Fuel Rail Pressure.
3. Verify DTC P0087 is not set in memory or the vehicle concern happens during high ambient temperatures and heavy load conditions.
- If DTC P0087 is set in memory or the vehicle concern is only present during high ambient temperatures and heavy load conditions
Refer to Fuel Injector Return Flow Test -- Enhanced Component Tests and General Diagnostics.
- If the vehicle concern is always present or occurs under other conditions
Refer to Pressure Relief Valve Test -- Engine Running

Pressure Relief Valve Test -- No Start

1. Remove the fuel pressure relief valve return hose and plug the hose to prevent fuel leakage.
2. Install a section of rubber fuel hose on the fuel pressure relief valve connection and place loose end of hose into a clean fuel container.
3. Crank or start the engine.
4. Verify no fuel leaks from the pressure relief valve.

Note: Before replacing the fuel pressure relief valve, ensure that the break-away torque is within specifications.

- If any fuel leaks from the fuel pressure relief valve.
Replace the fuel pressure relief valve Service and Repair.

- If no fuel leaks from the fuel pressure relief valve
Refer to Fuel Injector Return Flow Test Component Tests and General Diagnostics.

Pressure Relief Valve Test -- Engine Running

1. Remove the fuel pressure relief valve return hose and plug the hose to prevent fuel leakage.
2. Install a section of rubber fuel hose on the fuel pressure relief valve connection and place loose end of hose into a clean fuel container.
3. Engine at idle.
4. Verify no fuel leaks from the pressure relief valve.
- If any fuel leaks from the fuel pressure relief valve.
Replace the fuel pressure relief valve.
- If no fuel leaks from the fuel pressure relief valve
5. Engine running

Note: Repeat this step several times to test for a sticking fuel pressure relief valve.

6. Command the fuel pressure to 180 MPa (26,106 psi) with a scan tool for 2 minutes.
7. Verify no fuel leaks from the pressure relief valve.

Note: Before replacing the fuel pressure relief valve, ensure that the break-away torque is within specifications. Refer to Fastener Tightening Specifications Specifications.

- If any fuel leaks from the fuel pressure relief valve.
Replace the fuel pressure relief valve.

- If no fuel leaks from the fuel pressure relief valve
Refer to Fuel Injector Return Flow Test

Fuel Injector Return Flow Test

Note: Perform this test on both right and left bank of fuel injectors.

1. Remove the fuel return hose from the fuel injectors of one cylinder bank. Refer to Fuel Injection Fuel Return Pipe Replacement - Left Side or Fuel Injection Fuel Return Pipe Replacement - Right Side Service and Repair.
2. Install the J 45873 and J-45873-30 on the bank of fuel injectors.

Note:
- If the engine does not start, crank the engine in 15 second intervals, with 1 minute cooling time between intervals, until fuel starts to flow into all of the graduated cylinders.
- The engine cranking speed must be more than 150 RPM during the cranking portion of this test.

3. Start or crank the engine until fuel starts to flow into all 4 graduated cylinders.
4. Elevate the 4 yellow hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container and reinstall the hoses.
5. Crank or start the engine for 15 s.
6. Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for the initial fuel injector return flow values.
- If greater than the specified amount

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

6.1. Replace those fuel injectors that had high return flow and retest.
6.2. Repeat the return flow test and replace any additional injectors that measure greater than the specified amount. Refer to Fuel System Specifications for the retesting fuel injector return flow values Component Tests and General Diagnostics.

- If less than the specified amount
Refer to High Pressure Fuel Pump Test.

Fuel Injector Return Flow Test -- Enhanced

Important: Do not perform this testing unless the vehicle has the following symptoms.
- DTC P0087 sets in memory
- DTC P0087 only sets during high ambient temperatures and while the vehicle is under a heavy load
If the vehicle does not have the above symptoms, refer to Circuit/System Verification.
- Engine must be at operating temperature 83-87�C (181-189�F) for proper diagnosis.
- Perform this test on both the right and left bank of fuel injectors.

1. Engine at normal operating temperature, 83-87°C (181-189°F).
2. Remove the fuel return hose from the fuel injectors of one cylinder bank. Refer to Fuel Injection Fuel Return Pipe Replacement - Left Side or Fuel Injection Fuel Return Pipe Replacement - Right Side Service and Repair.
3. Install the J 45873 and J-45873-30 on the bank of fuel injectors.
4. Place the 4 yellow hoses into a suitable container.
5. Engine running until fuel flows from all 4 yellow hoses.
6. Engine at idle, command the fuel rail pressure to 120 MPa (17,400 psi) with a scan tool.

Note: It may be necessary to exit command after each cylinder to ensure commanded state does not time out.

7. With the rail pressure commanded to 120 MPa (17,400 psi), place each of the 4 yellow hoses one at a time into the 4 graduated cylinders for 30 s each.
8. Ignition OFF.
9. Measure and record the fuel return volume in each of the graduated cylinders.
10. Repeat Steps 1-9 on the opposite bank of injectors.
11. Add together the recorded injector return flow volumes of all 8 fuel injectors to determine the total injector return flow volume.
12. Verify the total injector return flow volume is greater than 144 ml.
- If the total injector return flow volume is less than 144 ml
Refer to High Pressure Pump Test.

- If the total injector return flow volume is 144 ml or greater
Replace any injector with an individual injector return flow volume of 18 ml or greater.

High Pressure Fuel Pump Test

1. Attempt to start the engine.
- Engine cranks but does not start
Replace the high pressure fuel injection pump
- The engine starts and runs
2. Engine at idle.
3. Command the fuel pressure control to 145 MPa (21,030 psi) with a scan tool.
4. Verify the Actual Fuel Rail Pressure is the same as the commanded fuel rail pressure.
- If the engine does not start or the actual fuel rail pressure is less than 145 MPa (21,030 psi)
Replace the high pressure fuel injection pump.
- The Actual Fuel Rail Pressure is 145 MPa (21,030 psi)
5. Engine speed above 1000 RPM.
6. Command the fuel pressure control to 180 MPa (26,106 psi) with a scan tool.
7. Verify the Actual Fuel Rail Pressure is the same as the commanded fuel rail pressure.
- If the actual fuel rail pressure is less than 180 MPa (26,106 psi)
Replace the high pressure fuel injection pump.
- The Actual Fuel Rail Pressure is 180 MPa (26,106 psi)
8. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure .

- Fuel Injection Pump Replacement Service and Repair
- Fuel Pressure Relief Valve Replacement Service and Repair
- Fuel Injector Replacement Service and Repair