If you are a diesel engine owner or operator, you may encounter a code that indicates high leakage in the high pressure fuel system (fuel rail pressure). This code will trigger both the malfunction indicator lamp (MIL) and the check engine light (CEL), but it will not cause any engine reactions, de-rate, or shutdown. This code is applicable for a three-filter fuel system that meets the EPA 07/10 emission standards.
The high pressure fuel system is responsible for delivering fuel to the injectors at the right pressure and timing. It consists of a high pressure fuel pump, a fuel rail, a fuel rail pressure sensor, a pressure limiting valve (PLV), and six fuel injectors. Any leakage in this system can affect the performance and efficiency of the engine, as well as increase the risk of fuel contamination and fire.
In this article, we will explain how to troubleshoot this code and identify the source of the leakage. We will also provide some tips on how to prevent and fix the leakage.
Step 1: Check for Other Fault Codes
The first step is to check for other fault codes that may be related to the high leakage code. One such code is 1077/14, which indicates low fuel pressure at the fuel rail. If this code is present, you must troubleshoot it first, as it can trigger the high leakage code as well. To check for fault codes, you can use the Detroit Diesel Diagnostic Link (DDDL) software, which connects to the engine’s electronic control module (ECM) and displays the diagnostic information.
Step 2: Perform an Automated Fuel System Integrity Check (FSIC)
The next step is to perform an automated fuel system integrity check (FSIC) using the DDDL software. This test will measure the time it takes for the fuel rail pressure to reach the desired value and to bleed off after the engine is turned off. The FSIC test will also indicate if there is any air in the fuel system, which can cause leakage and poor combustion.
To perform the FSIC test, follow these steps:
- Connect the DDDL software to the ECM and select the FSIC test from the menu.
- Turn the ignition key to the ON position, but do not start the engine.
- Follow the instructions on the screen and wait for the test to complete.
- Record the results of the test, especially the bleed off time and the air purge time.
The normal bleed off time for the high pressure fuel system is 35 seconds or more. If the bleed off time is longer than 35 seconds, it means that there is no significant leakage in the system. In this case, you can perform the same test while road testing the unit to see if the fault code comes back again. If it does not, you can release the unit or obtain driver information on the specific situation when the fault occurs.
If the bleed off time is less than 35 seconds, it means that there is a leakage in the system. In this case, you need to proceed to the next step to locate the source of the leakage.
Step 3: Check for Internal and External Fuel Leaks
The third step is to check for internal and external fuel leaks in the high pressure fuel system. Internal leaks are those that occur within the components of the system, such as the pump, the rail, the injectors, or the PLV. External leaks are those that occur outside the components, such as the fuel lines, the fittings, or the seals.
To check for internal and external fuel leaks, follow these steps:
- Visually inspect the high pressure pump fuel lines for kinks, damage, or loose fittings. Repair or replace as necessary.
- Visually inspect the fuel injector tubes and connections at the fuel rail for kinks, damage, or loose fittings. Repair or replace as necessary.
- Visually inspect the fuel rail pressure sensor for leaks or loose connections. Replace if leaking or loose.
- Visually inspect the fuel pump for external leaks, especially at the flanges. Replace if leaking.
- Cap all six injectors using tool J-48704, then attempt to start the engine. Using the DDDL software, monitor the rail pressure.
- If the rail pressure reaches the desired value, then check the rail pressure bleed down. If the rail pressure bleeds down by 100 bar or more in less than five minutes, then replace the high pressure fuel pump.
- If the rail pressure does not reach the desired value, then replace the high pressure fuel pump.
Step 4: Perform an Idle Speed Balance Test
The fourth step is to perform an idle speed balance test using the DDDL software. This test will measure the contribution of each cylinder to the engine’s power output at idle speed. The test will also indicate if any of the injectors are faulty or leaking.
To perform the idle speed balance test, follow these steps:
- Connect the DDDL software to the ECM and select the idle speed balance test from the menu.
- Start the engine and let it idle for at least five minutes.
- Follow the instructions on the screen and wait for the test to complete.
- Record the results of the test, especially the percentage values for each cylinder.
The normal percentage values for each cylinder should be between -70% and 70%. If any of the cylinders are above 70% or below -70%, it means that the corresponding injector is faulty or leaking. In this case, you need to proceed to the next step to isolate the injector.
Step 5: Isolate the Faulty or Leaking Injector
The fifth step is to isolate the faulty or leaking injector using tool J-48704. This tool is a cap that can be installed on each fuel injector transfer tube to block the fuel flow to the injector. By doing this, you can determine which injector is causing the leakage in the system.
To isolate the faulty or leaking injector, follow these steps:
- Remove each fuel injector transfer tube one at a time and install the cap tool J-48704 on the tube.
- Perform the FSIC test again and record the bleed off time.
- If the bleed off time is longer than 35 seconds, it means that the injector that was capped is faulty or leaking. Replace the injector and reset the injector trim codes using the DDDL software.
- If the bleed off time is still less than 35 seconds, it means that the injector that was capped is not faulty or leaking. Reinstall the injector transfer tube and repeat the process for the next injector.
Step 6: Inspect the PLV for Leaks
The sixth and final step is to inspect the PLV for leaks. The PLV is a valve that regulates the fuel pressure in the rail by releasing the excess fuel back to the tank. If the PLV is leaking, it can cause the rail pressure to drop and trigger the high leakage code.
To inspect the PLV for leaks, follow these steps:
- Install a clear hose to the PLV return line. Cap the PLV return line on the fuel filter module.
- Perform the FSIC test again and observe the clear hose for any fuel flow.
- If there is any fuel flow out of the PLV, it means that the PLV is leaking internally. Replace the PLV and reset the PLV counter to zero using the DDDL software.
- If there is no fuel flow out of the PLV, it means that the PLV is not leaking. Reconnect the PLV return line to the fuel filter module.