Fuel Injectors & Pumps – Section 8.1 Series 50/60 DDEC Cylinder Cutout Test

Section 8.1
Series 50/60 DDEC Cylinder Cutout Test

If a driver complains about cylinder miss and low power on a Series 50 or Series 60 engine, run a cylinder cutout test to identify the suspect injector. A cylinder cutout test may be run with either a Pro-Link reader or the Detroit Diesel Diagnostic Link (DDDL) PC software program. For current test steps, please refer to Series 60 service manual (6SE483) or Series 50 service manual (6SE50). Test options include an automatic test (all cylinders are automatically cutout in sequence) or a manual test (you can identify and cutout specific cylinders manually). This option is very helpful with a suspected injector. If the technician sees that there is a concern with #2 cylinder for example, swap injectors with a non-suspect injector. If the readings also change, then the injector is faulty. If it does not, then the injector is working properly. You may also choose to run the test at idle (1000 rpm recommended), or at free idle (manual setting via the cruise control switch or foot pedal). In this example, the automatic test at 1000 rpm is selected. After selecting the test parameters, start the test using DDDL. As the test begins you will see this screen, shown in figure 8-1.‪

Figure 1. Cylinder Cutout Start-Up Display

The engine should be at operating temperature before any cylinder cutout test is run. The first operation of this test will establish a baseline pulse width. The baseline pulse width is the pulse width being reported under the assumption all cylinders in the engine are firing. The program now begins to cut out each cylinder sequentially and record the new pulse width value with the engine performing on one less than the full number of cylinders. Because the engine is trying to maintain the same level of power output with one less cylinder active, the active cylinders will each get more fuel and a higher pulse width value will be recorded. The DDDL screen, shown in figure 8-2, shows the results.‪

Figure 2. Results of a Cylinder Cutout Test

You will notice that there has been a significant jump in the pulse width values of each cylinder except cylinder #2. This suggests that the baseline pulse width was actually measuring the pulse width of the engine when it was performing with five cylinders operating correctly. When each of the cylinders was cut out, the new pulse width recorded was actually reflecting the data with four cylinders running. The pulse width recorded when cylinder two was cut out remained essentially the same or even slightly below the baseline because this cylinder has a problem and was not contributing to engine output at the base line.‪

Under MISFIRING CYLINDER SECTION (faulty fuel injector) of the Series 60 service manual (6SE483) or Series 50 service manual (6SE50), the results of a cylinder cutout test state:‪

Scroll the list to review the results of the cylinder cutout test. To find suspect injector, look for a cylinder with a value that is within 0.2 degrees of the NO CUTOUT PULSE WIDTH, by comparing the CUTOUT PULSE WIDTH values to the NO CUTOUT PULSE WIDTH values.‪

1. If the CUTOUT PULSE WIDTH values are within 0.2 degrees of the NO CUTOUT PULSE WIDTH, shut down the engine and refer to “Faulty Fuel Injector Repair.”
2. If the CUTOUT PULSE WIDTH values are not within 0.2 degrees of the NO CUTOUT PULSE WIDTH, shut down the engine and refer to “ Faulty Electronic Control Module.”

The following tips will help run successful Cylinder Cutout Tests:‪

1. Please be aware that the cylinder cutout test results will be invalid if the engine load changes in the middle of a cylinder cutout test. This could result from such things as the engine fan or the air compressor turning on or off at any time during the cutout test.
2. While a load change in the middle of a test will invalidate the results, increasing the parasitic load on the engine prior to beginning the test will generally make test results easier to interpret. One way to increase the parasitic load is to turn on the air conditioning and set the blower to “High”.
3. Test results are generally easier to interpret when the test is run at 1,000 rpm rather than 600 rpm.
4. Pulse width readings for different engine types may vary widely. Pulse width readings also vary between different power ratings for the same engine. For detailed information on your particular engine model, please consult the service staff at your local Detroit Diesel service center.