3176 DIESEL TRUCK ENGINE PERFORMANCE TROUBLESHOOTING Caterpillar

Performance Troubleshooting

Usage:

Low Power/Poor Fuel Consumption Troubleshooting With A Dynamometer

Step 1

Interview the customer to determine the nature of the complaint, engine and vehicle configuration, application and operating conditions. The Performance Check List, Form No. SEHS8647, is available to record this information.

Step 2

Consider effect of non-engine related factors on the complaint. Vehicle efficiency, driver efficiency and operating conditions can have a dramatic effect on vehicle performance. For a complete explanation of each of these non-engine related factors, refer to the Truck Performance Diagnostic Guide, Form No. SEBD0808.

Step 3

Is maintenance tune-up due? If so, consider the effect and perform before proceeding further with diagnosis of the performance complaint.

Step 4

Electronics self check. Check the electronics diagnostic lamp on the vehicle dash to determine if there are any faults in the engine electronic system. Refer to, Engine Test Procedure Number P-200 to P-203 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Repair as required if a fault is detected. Consider the effect of any repair on the performance complaint before proceeding with step 5.

Step 5

Evaluate the impact of customer specified parameters on the complaint (include check of the personality module part no. and rating within a family). Verify that all parameters are correctly programmed (including pulses per mile) and the driver understands their effect on vehicle operation. Re-programming may be required. Refer to, Engine Test Procedure Number P-300 to P-303 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

Step 6

Check throttle sensor adjustment using the ECAP or the DDT service tools. Refer to, Engine Test Procedure Number P-700 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Adjust or repair as required.

Step 7

If the vehicle is equipped with a fuel heater, it should be turned "OFF" (automatically or manually) during moderate to warm weather operation. Fuel temperatures above 30°C (85°F) will reduce maximum potential horsepower but have little effect on fuel economy (refer to the Truck Performance Diagnostic Guide, Form No. SEBD0808, for further details).

Step 8

Measure fuel API. Lighter blended fuels will reduce maximum potential horsepower and decrease fuel economy (refer to the Truck Performance Diagnostic Guide, Form No. SEBD0808, for further details).

Step 9

Measure the fuel transfer pump pressure at rated engine rpm. The 1U5470 Engine Pressure Group can be used to measure the fuel transfer pump pressure. The 1U5470 Engine Pressure Group has a gauge to read fuel pressure to the fuel supply manifold. Special Instruction, Form No. SEHS8907 is with the tool group and gives information for its use.

NOTE: The ECAP or the DDT can also be used to check the fuel transfer pump pressure.

If the fuel transfer pump pressure is below 550 kPa (80 psi) at rated rpm, check for:

* Restrictions in the low pressure fuel system (plugged fuel filter, collapsed hoses, etc.).

* Air in the fuel.

* Fuel transfer pump wear. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR3908.

* Excessive fuel return to the tank.

Step 10

Check fuel injection timing. Refer to, Engine Test Procedure Number P-402 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Check the actual versus desired timing.

Step 11

Perform the PAR Chassis Dynamometer Test. [This test includes measurement of fuel temperature, fuel API, inlet manifold air temperature, and barometer to correct WHP (wheel horsepower) to standard conditions].

Step 12

Evaluation of the PAR Chassis Dynamometer Test results:

A. Acceptable fuel rate, boost, and corrected WHP. Engine performance is acceptable and not a contributor to any lack of vehicle performance.

1. If measured and corrected WHP are essentially equal the complaint can not be verified.

2. If measured WHP is significantly less than corrected WHP, operating conditions are creating a loss of vehicle performance. One or more of the following conditions must exist: fuel temperature above 30°C (85°F), (check for fuel heater); fuel API above 35; barometer below 30.5 in. Hg; inlet manifold air temperature above 43°C (110°F). The probable result of high ambient air temperature, poor airflow across the aftercooler, or a plugged aftercooler.

B. High fuel rate and high WHP.

1. Check the selected rating and full load static and full torque static values (compare values stamped into the engine information plate on the valve cover to those programmed into the ECM). If incorrect, obtain Level 3 Security (factory passwords) and reprogram as necessary. Repeat the PAR Chassis Dynamometer Test to validate the effect.

2. If the settings and the rating are correct, replace the unit injectors.

NOTE: Only consider replacing unit injectors if maximum fuel rate has increased more than 10% of the nominal specification for a new engine. Then investigate the source of fuel contamination.

High fuel rate, if accompanied by increased hp, is not necessarily the cause of poor performance (fuel economy). Some increase in maximum potential fuel rate may occur as an engine matures (first 100,000 miles). The amount of fuel rate increase is totally dependent upon fuel cleanliness. Small particles of debris in the fuel erode areas of greatest restriction within the high pressure fuel system. As this erosion occurs, the fuel injection system allows more fuel to be injected into each cylinder. However, engine fuel efficiency (ability to convert fuel into hp) is not effected because the increased fuel produces additional hp. For a given operating condition (hp demand), the driver will unconsciously adjust throttle position to reduce fuel delivery and hp output. At full power conditions more fuel is consumed but more work is performed. Plus full power operation is normally a very small percentage of the total operating cycle of the vehicle. Maximum potential fuel rate stabilizes as efficiency is maximized beyond 100,000 miles.

C. Acceptable fuel rate, low boost and corrected WHP/high fuel rate, acceptable or low WHP and boost.

1. Inspect the air induction system for the following:

* Boost/exhaust leaks.

* Inlet/exhaust restrictions.

* Aftercooler restrictions.

2. Check fuel injection timing. Refer to, Engine Test Procedure Number P-402 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Check the actual versus desired timing.

3. Visually inspect the turbocharger compressor and turbine wheels for damage. Check freeness of the rotating assembly and measure wheel end play and run out. If a problem is found, replace the turbocharger.

D. Low fuel rate, boost, and WHP.

1. Inspect the air induction system for the following:

* Boost/exhaust leaks.

* Inlet/exhaust leaks.

* Aftercooler restrictions.

2. Install an ECAP. Refer to, Engine Test Procedure Number P-201 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

a. Check for fault codes. Refer to, Engine Test Procedure Number P-202 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

b. If a fault is found, refer to Engine Fault Code in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913 for further diagnostics.

3. Use an ECAP or DDT to compare measured fuel position with desired fuel position at rated rpm and peak torque rpm conditions (requires a chassis dynamometer or road test).

If the fuel position is limited to the FRC setting, check the boost sensor for proper operation. Refer to, Engine Test Procedure Number P-601 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

4. Use an ECAP or DDT to turn off one cylinder at a time. Follow the steps that follow:

a. Start the engine.

b. Install the service tool and "T "harness to the data link.

* For the ECAP, select the "Interactive Diagnostics" screen.

* For the DDT, select "Cylinder 1 Change Function".

c. Operate the engine at low idle.

d. Cutout one cylinder at a time.

* IF a cylinder is not performing properly, little audible change will be noticed when that cylinder is cutout.

* If a cylinder(s) is determined to be performing improperly, refer to Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913 or Mechanical Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR4248 for further diagnostics.

* If no problems are found during cylinder cutout, proceed to step 5.

5. Measure fuel transfer pump pressure at rated engine rpm. If fuel transfer pump pressure is low, check for:

* Restrictions in the low pressure fuel system (plugged fuel filter, collapsed hoses, etc.).

* Air in the fuel.

* Fuel transfer pump wear. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR3908.

* Excessive fuel return to the tank.

6. Check the unit injector part number to verify correct parts.

7. Test unit injectors for possible low fuel flow due to debris.

Low Power/Poor Fuel Consumption Troubleshooting Without A Dynamometer

1. Interview the customer to determine the nature of the complaint, engine and vehicle configuration, application and operating conditions. The Performance Check List, Form No. SEHS8647, is available to record this information.

2. Consider effect of non-engine related factors on the complaint. Vehicle efficiency, driver efficiency and operating conditions can have a dramatic effect on vehicle performance. For a complete explanation of each of these non-engine related factors, see the Truck Performance Diagnostic Guide, Form No. SEBD0808.

3. Is maintenance tune-up due? If so, consider the effect and perform before proceeding further with diagnosis of the performance complaint.

4. Electronics self check. Check the electronics diagnostic lamp on the vehicle dash to determine if there are any faults in the engine electronic system. Refer to, Engine Test Procedure Number P-200 to P-203 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Repair as required if a fault is detected. Consider effect of any repair on the performance complaint before proceeding with step 5.

5. Evaluate the impact of customer specified parameters on the complaint (include check of the personality module part no. and rating within a family). Verify that all parameters are correctly programmed (including pulses per mile) and the driver understands their effect on vehicle operation. Re-programming may be required. Refer to, Engine Test Procedure Number P-300 to P-303 in Electronic Troubleshooting, 3176 Diesel Truck Engine, SENR3913.

6. Check throttle sensor adjustment using the ECAP or the DDT service tools. Refer to, Engine Test Procedure Number P-700 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Adjust or repair as required.

7. If the vehicle is equipped with a fuel heater, it should be turned "off" (automatically or manually) during moderate to warm weather operation. Fuel temperatures above 30°C (85°F) will reduce maximum potential horsepower but have little effect on fuel economy (refer to the Truck Performance Diagnostic Guide, Form No. SEBD0808, for further details).

8. Measure fuel API. Lighter blended fuels will reduce maximum potential horsepower and decrease fuel economy (see the Truck Performance Diagnostic Guide, Form No. SEBD0808, for further details).

9. Measure the fuel transfer pump pressure at rated engine rpm. The 1U5470 Engine Pressure Group can be used to measure the fuel transfer pump pressure. The 1U5470 Engine Pressure Group has a gauge to read fuel pressure to the fuel supply manifold. Special Instruction, Form No. SEHS8907 is with the tool group and gives information for its use.

NOTE: The ECAP or the DDT can also be used to check the fuel transfer pump pressure.

If the fuel transfer pump pressure is low, check for:

* Restrictions in the low pressure fuel system (plugged fuel filter, collapsed hoses, etc.).

* Air in the fuel.

* Fuel transfer pump wear. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR3908.

* Excessive fuel return to the tank.

10. Check fuel injection timing. Refer to Engine Test Procedure Number P-402 in the Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. Check the actual versus desired timing.

11. Perform the Engine Performance Load Test (no dynamometer). Measure fuel temperature at the filter base, inlet manifold pressure, and inlet manifold temperature at several engine rpm's.

12. Evaluation of the Engine Performance Load Test (no dynamometer) results:

a. Inspect the air induction system for the following:

* Boost/exhaust leaks.

* Inlet/exhaust leaks.

* Aftercooler restrictions.

b. Install an ECAP. Refer to, Engine Test Procedure Number P-201 in the Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

1. Check for fault codes. Refer to, Engine Test Procedure Number P-202 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

2. If a fault is found, refer to Engine Fault Code in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913 for further diagnostics.

c. Use an ECAP or DDT to compare measured fuel position with desired fuel position at rated rpm and peak torque rpm conditions (requires a chassis dynamometer or road test).

d. Use an ECAP or DDT to turn off one cylinder at a time. Follow the steps that follow:

1. Start the engine.

2. Install the service tool and "T" harness to the data link.

* For the ECAP, select the "Interactive Diagnostics" screen.

* For the DDT, select "Cylinder 1 Change Function".

3. Operate the engine at low idle.

4. Cutout one cylinder at a time.

* If a cylinder is not performing properly, little audible change will be noticed when that cylinder is cutout.

* If no problems are found during cylinder cutout, proceed to step 5.

5. Measure fuel transfer pump pressure at rated engine rpm. If fuel transfer pump pressure is low, check for:

* Restrictions in the low pressure fuel system (plugged fuel filter, collapsed hoses, etc.).

* Air in the fuel.

* Fuel transfer pump wear. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR3908.

* Excessive fuel return to the tank. Test unit injectors for possible low fuel flow due to debris.

Performance Analysis Report (PAR) Chassis Dynamometer Test

Required Equipment For Test:

Optional Equipment:

NOTE: Refer to the latest PAR instructions, Special Instruction Form No. SEHS8025, for more detailed instructions concerning preparation of the truck, proper use of the dynamometer and use of the Technical Information File microfiche.

Use the following procedure for the PAR Chassis Dynamomenter test:

1. Check the fuel API if not done in another procedure. Refer to, Special Instruction, Form No. GMGO0977.

2. Record data from the Engine Information Plate.

3. Install the required measurement instruments on the engine.

4. Operate the engine at partial throttle and load to obtain the normal operating temperature, and then operate the engine at full load for two minutes. While operating at full load, check the fuel pressure [approximately 550 kPa (80 psi)]. If the pressure is low, perform Procedure No. 113T (part of Truck Performance Diagnostic Guide, Form No. SEBD0808), before continuing the test.

5. Beginning from Top Engine Limit, load the engine to each test rpm, ± 5 rpm, for at least two minutes for proper stabilization.

6. Record engine test information, in sequence if possible, on the record sheets. If repeat runs are required to complete the sheets, be sure temperatures and conditions are as equal as possible.

7. Recheck the first lug rpm to confirm stability of the test. Compare the results to the original check. If more than a two percent difference exists in any data, rerun the test. Either conditions were not stable or there is a problem with the test equipment or the dynamometer.

8. Check timing advance operation by observing rpm and timing on the ECAP with the 7X1200, Timing Adapter Tool Group installed. Refer to, Engine Test Procedure Number P-402, in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

9. Using the Correction Factor Worksheet, Procedure No. 2000R (part of Truck Performance Diagnostic Guide, Form No. SEBD0808), calculate the corrected wheel horsepower.

10. Evaluate the fuel rate, inlet manifold pressure, and timing. Refer to the Guidelines For Evaluation Of Test Results.

NOTE: Factory performance specifications only apply to engines with FLS (full load static) and FTS (full torque static) values set to specification.

Engine Performance Load Test (No Dynamometer)

Required Equipment For Test:

Optional Equipment:

Use the following procedure for the Engine Performance Load Test (No Dynamometer):

1. Check the fuel API if not done in another procedure. Refer to, Special Instruction, Form No. GMG00977.

2. Record data from the Engine Information Plate.

3. Install the required measurement instruments on the engine.

4. Select the engine rpm's to be tested (minimum of two points, but no more than four).

5. Operate the vehicle under load to obtain normal operating temperature of the engine and drive train.

6. Slowly load the engine from Top Engine Limit.

7. Maintain a stable rpm at each pre-selected test rpm for consistent results. If stable rpm cannot be maintained, the test data may not be accurate enough to evaluate.

8. Record the engine test information, in sequence if possible, on the record sheets. If repeat runs are required to complete the sheets, be sure temperatures and conditions are as equal as possible.

9. Recheck the first lug rpm to confirm stability of the test. Compare results to original check. If more than a two percent difference exists in any of the data, rerun the test. Either the conditions were not stable or there is a problem with the test equipment or the dynamometer.

10. Check timing advance operation by observing rpm and timing on the ECAP with the 7X1200, Timing Adapter Tool Group installed. Refer to, Engine Test Procedure Number P-402, in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.

11. Using the Correction Factor Worksheet, Procedure No. 2000R, (part of Truck Performance Diagnostic Guide, Form No. SEBD0808), calculate the corrected wheel horsepower.

12. Evaluate the fuel rate, inlet manifold pressure, and timing. Refer to the Guidelines For Evaluation Of Test Results.

NOTE: Factory performance specifications only apply to engines with FLS (full load static) and FTS (full torque static) values set to specification.