Fuel Pressure: Testing and Inspection

CHECKING THE FUEL DELIVERY SYSTEM

For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.






WARNING: Follow these safety precautions to reduce the risk of fire and possible serious or fatal injury when performing this test procedure.
- Fuel or fuel vapors are highly flammable. A fire could occur if an ignition source is present. Do not expose the fuel or the test equipment used in this procedure to open flames or sparks.
- Inhalation of fuel vapors could lead to disorientation and personal injury. Keep the service area well ventilated, or perform this test procedure in an area where there is a building exhaust removal system.
- Relieve fuel system pressure before servicing fuel system components.
- Use extreme caution when connecting and disconnecting fuel lines.
- Considerable fuel leakage may occur when servicing the fuel system. Wear protective eyewear and clothing to protect from fuel splash, and take suitable fuel containment measures.
- Wrap a shop towel around the fuel pressure gauge connection to absorb fuel leakage that occurs when connecting the test equipment. Place the towel in an approved container when complete.
- Never store fuel in an open container due to the possibility of fire or explosion. Have a dry chemical (Class B) fire extinguisher nearby.
- High-pressure fuel lines deliver diesel fuel under extreme pressure from the injection pump to the fuel injectors. This may be as high as 26,107 psi (1800 bar). Use extreme caution when inspecting for high-pressure fuel leaks. Fuel under this amount of pressure can penetrate skin causing possible serious or fatal injury.

1. VISUALLY CHECK THE FUEL DELIVERY SYSTEM FOR LEAKS AND DAMAGE

NOTE: Make sure that both batteries are fully charged before proceeding. A weak battery can cause inaccurate fuel volume readings.

1. Turn the ignition off.
2. Visually inspect the Fuel Delivery System for external leaks and damage.
3. Visually inspect the Fuel tank vents and hoses for any signs of a possible restriction or plugging.

Is the system leaking, plugged, or damaged?

Yes

- Repair or replace as necessary.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 2

2. CHECKING FUEL QUALITY/CONTAMINATION
1. Collect a fuel sample from the vehicle in a clean transparent container.
2. Collect a fuel sample of fresh clean fuel in a clean transparent container for reference.
3. Check the fuel sample for the following:
- Check the color of the fuel. Diesel fuel will generally be a yellow color.
- Allow the fuel to settle and look for cloudiness indicating contamination.
- Check the volatility of the fuel.
- Look for a parting line in the fuel sample indicating another type of liquid mixed with the fuel.
- Look for any signs of debris in the fuel sample.

Are there any signs of contamination or poor quality detected?

Yes

- Replace the Fuel Filter and flush the entire fuel system. Replace with clean fuel and continue with procedure to check for damage to the fuel system components.
- Go To 3

No

- Go To 3

3. SETUP TO CHECK IN-TANK FUEL LIFT PUMP FLOW

Is the Gas and Diesel Fuel/Pressure Decay Tester 8978 available?

Yes

- Go To 4

No

- Go To 7

4. IN-TANK FUEL LIFT PUMP FLOW TEST WITH DECAY TESTER





NOTE: Before performing the IN-TANK FUEL LIFT PUMP FLOW test, verify that the fuel level in the fuel tank is above 1/4 full. If fuel tank is not above 1/4 full the pump will take in air causing the test results to be inaccurate.

1. Disconnect the low pressure fuel supply line from the High Pressure Fuel Pump. Connect the 5/16 Quick Connect Fitting 8978-2 from the Gas and Diesel Fuel/Pressure Decay Tester 8978 to the low pressure fuel supply line.
2. Connect the Fuel Pressure Gauge Assembly Fuel Inlet Hose 8978-1 (1) to the 5/16 Quick Connect Fitting 8978-2.
3. Connect the Drain Extension Hose 535680 (2) to the Fuel Pressure Gauge Assembly Drain Hose (4).
4. Connect the Reservoir Assembly 534960 (3) to the Drain Extension Hose 535680 (2).






WARNING: To reduce the risk of fire and serious possible serious or fatal injury, place the Reservoir Assembly 534960 (3) on the floor and out of the way so that it is not a trip hazard.

5. Perform the following to purge air from the system:
- With the scan tool, actuate the In-Tank Fuel Lift Pump Module.
- Open the Flow Test Valve and allow the fuel to flow into the Reservoir for 10 seconds, then close the Flow Test Valve.
- Turn the ignition off.
- Disconnect, empty, and then reconnect the Reservoir Assembly.

6. Perform the following three times to find the average flow rate:
- With the scan tool, actuate the In-Tank Fuel Lift Pump Module.
- Open the Flow Test Valve (1) for 10 seconds, then close the Valve.
- Turn the ignition off.
- Measure and record the amount of fuel in the Reservoir Assembly.
- Disconnect, empty, and then reconnect the Reservoir Assembly.

7. Add the three recorded measurements and then divide the total by three to calculate the average flow rate. The flow rate is 500 ml in 10 seconds.

Does the average flow rate meet or exceed the specification?

Yes - Vehicle starts and runs:

- Go To 10

Yes - Vehicle is a no start:

- Go To 15

No

- Leave the special tools installed. Replace the Fuel Filter/Water Separator. During Fuel Filter replacement, be sure to check and clean the secondary filter screen in the filter head outlet.
- Go To 5

5. RECHECK IN-TANK FUEL LIFT PUMP FLOW




1. Perform the following to purge air from the system:
- With the scan tool, actuate the In-Tank Fuel Lift Pump Module.
- Open the Flow Test Valve (1) for 10 seconds, then close the Valve.
- Turn the ignition off.
- Disconnect, empty, and then reconnect the Reservoir Assembly (2).

2. Perform the following three times to find the average flow rate:
- With the scan tool, actuate the In-Tank Fuel Lift Pump Module.
- Open the Flow Test Valve (1) for 10 seconds, then close the valve.
- Turn the ignition off.
- Measure and record the amount of fuel in the Reservoir Assembly (2).
- Disconnect, empty, and then reconnect the Reservoir Assembly (2).

3. Add the three recorded measurements and then divide the total by three to calculate the average flow rate. The flow rate is 500 ml in 10 seconds.

Does the average flow rate meet or exceed the specification?

Yes

- Go To 6

No

- Use the wiring diagram as a guide to check the In-Tank Fuel Lift Pump wiring for an open, high resistance, or short to ground. If the In-Tank Fuel Lift Pump wiring is ok, remove the fuel tank and replace the In-Tank Fuel Lift Pump Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. CHECKING THE PRESSURE LIMITING VALVE PRESSURE LIMITING VALVE COUNTER
1. Turn the ignition on.
2. With the scan tool, view the Pressure Limiting Valve counter and Pressure Limiting Valve timer.

Is the counter higher than 50 or the timer higher than 5 hours?

Yes

- Replace the Pressure Limiting Valve. When Pressure Limiting Valve replacement is complete, use the scan tool to reset the Pressure Limiting Valve counter and timer. This command is in the PCM Misc Functions.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Test complete.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

7. IN-TANK FUEL LIFT PUMP FLOW TEST WITHOUT DECAY TESTER

NOTE: Before performing the IN-TANK FUEL LIFT PUMP FLOW test, verify that the fuel level in the fuel tank is above 1/4 full. If fuel tank is not above 1/4 full the pump will take in air causing the test results to be inaccurate.

1. Disconnect the low pressure fuel supply line from the High Pressure Fuel Pump. Install fuel system test fitting 9863 onto the end of the low pressure fuel supply line. Then, connect one end of a section of fuel hose to the test fitting and place the other end of the fuel hose into an empty fuel container.
2. Turn the ignition on.
3. With the scan tool, actuate the In-Tank Fuel Lift Pump Module.
4. With the In-Tank Fuel Lift Pump Module running, place the fuel hose into a 1,000 ml graduated cylinder for 10 seconds and then return the hose to the fuel container.

CAUTION: Stop all actuations.

5. Turn the ignition off.
6. Measure the amount of fuel in the graduated cylinder. The fuel output specification is 590 ml in 10 seconds.

Does the amount of fuel in the graduated cylinder meet or exceed the specification?

Yes - Vehicle starts and runs:

- Go To 10

Yes - Vehicle is a no start:

- Go To 15

No

- Leave the tools installed. Replace the Fuel Filter/Water Separator. During Fuel Filter replacement, be sure to check and clean the secondary filter screen.
- Go To 8

8. RECHECK THE IN-TANK FUEL LIFT PUMP FLOW
1. Turn the ignition on.
2. With the scan tool, actuate the In-Tank Fuel Lift Pump Module.
3. With the lift pump running, place the fuel hose into a 1,000 ml graduated cylinder for 10 seconds and then return the hose to the fuel container.

CAUTION: Stop all actuations.

4. Turn the ignition off.
5. Measure the amount of fuel in the graduated cylinder. The fuel output specification is 590 ml in 10 seconds.

Does the amount of fuel in the graduated cylinder meet or exceed the specification?

Yes

- Go To 9

No

- Use the wiring diagram as a guide to check the In-Tank Fuel Lift Pump wiring for an open, high resistance, or short to ground. If the In-Tank Fuel Lift Pump wiring is ok, remove the fuel tank and replace the In-Tank Fuel Lift Pump Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

9. CHECKING THE PRESSURE LIMITING VALVE PRESSURE LIMITING VALVE COUNTER
1. Turn the ignition on.
2. With the scan tool, view the Pressure Limiting Valve counter and Pressure Limiting Valve timer.

Is the counter higher than 50 or the timer higher than 5 hours?

Yes

- Replace the Pressure Limiting Valve. When Pressure Limiting Valve replacement is complete, use the scan tool to reset the Pressure Limiting Valve counter and timer. This command is in the PCM Misc Functions.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Test complete.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

10. CHECKING THE FUEL CONTROL ACTUATOR
1. Reconnect the fuel supply hose.
2. Start the engine.
3. With the scan tool, navigate to Systems Tests and select the Fuel Pressure Override Test.
4. Allow the engine speed and fuel pressure to ramp up and stabilize and then stop actuation.

Does the engine speed and fuel pressure ramp up and stabilize when actuated and then come back to rest at idle and stabilize when actuation is stopped?

Yes

- Go To 11

No

- Replace the Fuel Control Actuator.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

11. PRESSURE LIMITING VALVE PRESSURE LIMITING VALVE





NOTE: In the illustration provided, the pressure-limiting valve location is indicated by the number (1).

1. Turn the engine off, ignition on.
2. With the scan tool, view the Pressure Limiting Valve counter and Pressure Limiting Valve timer. If the counter is above 50 or the timer is above 5 hours, the Pressure Limiting Valve must be replaced before continuing with this test.
3. Turn the ignition off.
4. Remove the banjo bolt from the Pressure Limiting Valve on the fuel rail.
5. Install fuel system test fitting (9012) into the Pressure Limiting Valve.
6. Attach one end of a fuel hose to the fuel fitting and put the other end of the fuel hose into a container.

NOTE: NOTE: Do not drive the vehicle with any portion of this test kit installed.

7. Start the engine and operate the engine at idle. Watch for fuel flow into the fuel container.
8. While the engine is at idle, actuate the Fuel Pressure Override Test with the scan tool. Watch for fuel flow into the fuel container.

NOTE: There should be no fuel flow into the container.

Is fuel flowing into the container?

Yes

- Replace the Pressure Limiting Valve.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 12

12. ENGINE RUNNING INJECTOR RETURN FLOW TEST

NOTE: This purpose of this test is to determine if the Fuel Injectors are leaking internally into the fuel return.

1. Operate the engine until the coolant temperature is above 82.2°C (180°F).
2. Turn the engine off.
3. Remove the banjo connector from the fuel drain tube at the rear of the fuel filter housing.
4. Install fuel system test fitting 9012 in place of the banjo connector.
5. Remove the vehicle fuel return line from the engine fuel drain tube.
6. Install a piece of fuel line onto the test fitting and into a fuel container or into the fuel tank.
7. Install a second test hose onto the fuel drain tube. Place the other end of the test hose into a fuel container.
8. Start engine and allow it to idle for 30 seconds. This step allows the flows to stabilize.
9. Using the scan tool, navigate to PCM view -> PCM Cummins -> More Options-> System Tests -> Fuel Pressure override test. Select Start, then press Next.
10. Press the Run button on the screen. As you press the Run button to start the override test, move the injector return hose from the bucket and insert into the appropriate measuring device. The engine speed will elevate rapidly to 1,200 rpm and the rail pressure will increase to 20,000 psi (1,400 bar).
11. While the test is running, record the FCA duty cycle % and actual rail pressure. Record the readings on the Cummins Diesel Diagnostic Worksheet located under e-files, service, Star center in dealerconnect.
12. Measure and Record the amount of fuel collected.
13. If the flow is less than 160 ml for 30 seconds, the test has successfully passed.
14. If the flow is greater than 160 ml for 30 seconds after step 11, shut off the engine and remove all 6 high pressure fuel lines. Re-torque the high-pressure connector nut. Inspect for damage, repair/replace as necessary. Reinstall high pressure fuel lines.
15. Start the engine and repeat steps 8 through 12.
16. Measure the amount of fuel in the graduated cylinder.
17. If the amount of fuel is greater than 160 ml for 30 seconds, shut off the engine and remove the #1 high pressure fuel line. Cap the #1 Fuel Injector port using tool 9864 on the fuel rail and repeat steps 7 through 12.
18. Measure the amount of fuel in the graduated cylinder. If the amount is less than 160 ml for 30 seconds, remove and replace the #1 Fuel Injector and #1 high pressure connector.
19. If the amount of fuel is not less than 160 ml for 30 seconds, repeat steps 18-19 for cylinders 2-6 until the leaking Fuel Injector is found.

Did the vehicle pass the Injector Return Flow test at step 13 without any repairs needed?

Yes

- Go To 13

No

- Perform the necessary repairs and verify fuel system operation.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

13. HIGH PRESSURE FUEL PUMP RETURN FLOW TEST
1. Turn the engine off.
2. Remove the banjo connector from the fuel drain tube at the rear of the fuel filter housing.
3. Install fuel system test fitting 9012 in place of the banjo connector.
4. Install a piece of fuel line onto the test fitting and put the open end into the graduated cylinder.
5. Start the engine and let it idle for one minute.
6. Measure the amount of fuel in the graduated cylinder.
7. The fuel flow should be less than 1,000 ml/minute at idle.

Is the flow less than 1,000 ml/minute at idle?

Yes

- Go To 14

No

- Replace the High Pressure Fuel Pump.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

14. HIGH PRESSURE FUEL PUMP PERFORMANCE TEST
1. Disconnect the Fuel Control Actuator harness connector.
2. Disconnect high pressure fuel line from the fuel rail and route the high pressure fuel line into a graduated cylinder.
3. Crank the engine until fuel exits this line. This will not be high pressure fuel.
4. Crank the engine for three 10 second intervals.

NOTE: This will give you 30 total seconds of flow time. These are broken into three separate intervals to prevent damage to the starter.

5. Fuel flow specification's based on engine cranking speed. If you do not collect the stated amount of fuel in 30 seconds, replace the pump:
- Minimum fuel pump flow at 150 rpm cranking speed is 70 ml.
- Minimum fuel pump flow at 200 rpm cranking speed is 90 ml.

Does the fuel flow exceed the minimum specification?

Yes

- The fuel system is operating normally. Check for any Service Bulletins that may apply.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace the High Pressure Fuel Pump.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

15. PRESSURE LIMITING VALVE PRESSURE LIMITING VALVE (NO START)





NOTE: In the illustration provided, the pressure-limiting valve location is indicated by the number (1).

1. Turn the engine off, ignition on.
2. With the scan tool, view the Pressure Limiting Valve counter and Pressure Limiting Valve timer. If the counter is above 50 or the timer is above 5 hours, the Pressure Limiting Valve must be replaced before continuing with this test.
3. Reconnect the fuel supply hose.
4. Remove the banjo bolt from the Pressure Limiting Valve on the fuel rail.
5. Install fuel system test fitting 9012 into the Pressure Limiting Valve.
6. Attach one end of a fuel hose to the fuel fitting and put the other end of the fuel hose into a container.
7. Crank the engine and look for fuel leaking from the Pressure Limiting Valve.

NOTE: There should be no fuel flow into the container.

Is fuel flowing into the container?

Yes

- Replace the Pressure Limiting Valve.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 16

16. INJECTOR RETURN FLOW TEST DURING ENGINE CRANKING @200 RPM (NO START)
1. Install fuel system fitting 9012 in standard location on back of fuel filter head to measure pump and injector return flows.
2. Install hoses to the test fitting and the injector return line and route them to a bucket or other container. Make sure test lines are straight and slope downward their entire length. This is to avoid trapping air/fuel in the lines while testing.
3. Unplug the injector harnesses at the valve cover, unplug the connector to the FCA.
4. Crank the engine for least 10 seconds until fuel starts to flow out of the pump and injector return hoses. Turn Key off when finished.
5. Let all the fuel drain out of each line before continuing.
6. Place the injector return hose into an appropriate measuring device.
7. Crank the engine for 10 seconds. Go from key off, to crank, and back to key off. Do not leave the ignition on between tests.
8. Let all of the fuel drain out of the injector hose.
9. Record the amount of injector return flow volume for a 10 second crank.
10. Flow should be less than 40 ml for 10 seconds of cranking.
11. If the flow is greater than 40 ml after step 10, remove the #1 fuel injector supply line. Re-torque the high-pressure connector nut. Cap the #1 Fuel Injector port using tool 9864 on the fuel rail.
12. Crank the engine and perform steps 7 through 9.
13. Measure the amount of fuel in the graduated cylinder.
14. If the amount of fuel is less than 40 ml, remove the #1 high pressure connector and the #1 Fuel Injector. Inspect for damage, repair/replace as necessary.
15. If the amount of fuel is not less than 40 ml, repeat this procedure for cylinders 2-6.
16. Install all high-pressure connectors, Fuel Injectors, and Fuel Injector supply lines. Repeat steps 1-9 to confirm repair.

Did the vehicle pass the Injector Return Flow test without any repairs needed?

Yes

- Go To 17

No

- Perform the necessary repair.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

17. HIGH PRESSURE FUEL PUMP PERFORMANCE TEST (NO START)
1. Turn the engine off.
2. Disconnect fuel line and the fuel system test fitting 9012.
3. Reconnect the banjo connector to the drain tube.
4. Disconnect the FCA harness connector.
5. Disconnect high pressure fuel line from the fuel rail and route the high pressure fuel line into a graduated cylinder.
6. Crank the engine until fuel exits this line. This will not be high pressure fuel.
7. Crank the engine for three 10 second intervals.

NOTE: This will give you 30 total seconds of flow time. These are broken into three separate intervals to prevent damage to the starter.

8. Fuel flow specification's based on engine cranking speed. If you do not collect the stated amount of fuel in 30 seconds, replace the pump:
- Minimum fuel pump flow at 150 rpm cranking speed is 70 ml.
- Minimum fuel pump flow at 200 rpm cranking speed is 90 ml.

Does the fuel flow exceed the minimum specification?

Yes

- The fuel system is operating normally. Check for any Service Bulletins that may apply.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace the High Pressure Fuel Pump.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.