3176 PERFORMANCE TROUBLESHOOTING Caterpillar

Performance Troubleshooting

Usage:

Low Power/Poor Fuel Consumption Troubleshooting With 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, refer to 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; Logged Fault Codes. Check the electronic system for logged fault codes. Examine for faults that are indicated by; (1) diagnostic lamp on vehicle dash and (2) fault screen on ECAP. Determine if correlation exists between customer complaint and possible problems as related to fault codes. Refer to the "Troubleshooting Diagnostic Codes" section in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. Repair as required if a fault is detected. Consider the 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 the "Programming 3176 Parameters" section in the Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

6. Check throttle position sensor (% duty cycle) adjustment using the ECAP or the DDT service tools. Throttle position sensor/duty cycle is displayed on the "Monitor/Calibrate Sensors"-"Monitor Throttle Position Sensor Signal" screen. Refer to Engine Test Procedure Number P-303 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. 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 (refer to 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. 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 445 kPa (65 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 or damage. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR5107.

* Excessive fuel return to the tank due to a malfunction of the fuel pressure regulating valve in the siphon block.

10. Check fuel injection timing. Refer to, Engine Test Procedure Number P-221 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. Check the actual versus desired timing.

11. Use the ECAP and the 7X1201 Timing Adapter to monitor the injection signal duration. The duration bars should remain close in length.

NOTE: Leave the 7X1201 Timing Adapter installed for remainder of testing to monitor injection duration under all conditions.

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

A. 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".

B. Start the engine.

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. The injection signal duration for the firing cylinders should increase slightly to make up for the cutout cylinder.* If a cylinder(s) is determined to be performing improperly, refer to Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112 or Mechanical Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112 or Mechanical Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5113 for further diagnostics.* If no problems are found during cylinder cutout, proceed to step 13.

13. Verify fuel position (rack) using the steps that follow:

A. Lug engine in full load condition to problem rpm.

B. Use an ECAP or DDT (status screen) to compare fuel position (rack) with rated fuel position and FRC fuel position. Fuel position (rack) is limited by FRC fuel position until boost is sufficient. Once sufficient boost is available, fuel position (rack) is limited by rated fuel position. Under full throttle/load the fuel position should closely follow rated fuel position.

C. If the fuel position is limited to FRC fuel position, check the transducer (boost) module and supply lines for correct operation.

D. If the fuel position is not limited by FRC fuel position and the fuel position is less than rated fuel position, check throttle position sensor operation and adjustment. Refer to Engine Test Procedure Number P-211 and P-303 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

14. Measure horsepower contribution of each cylinder, under full load condition using the steps that follows:

A. Bring engine up to normal operating temperature.

B. Lug engine to the problem rpm. Let the engine stabilize and record the WHP (wheel horsepower) reading (6 cylinders active).

C. Use the ECAP or DDT interactive diagnostics to cut out one cylinder at a time. Let the engine speed stabilize to the previous rpm and record the WHP reading (5 cylinders active).

NOTE: Only cut out one cylinder at a time.

D. Compare the WHP (wheel horsepower) loss of each cylinder. Power loss difference between cylinders should be less than 10 WHP (wheel horsepower). The cylinder with the smallest WHP (wheel horsepower) loss is the weak cylinder.

To Diagnose The Weak Cylinder:

E. Verify the Electronic Unit Injector is the correct part number.

F. Remove and test unit injectors for possible low fuel flow due to plugged orifices. Also examine injectors for indication of combustion leakage. Inadequate injector cone to cylinder head sleeve sealing may allow combustion gas to enter fuel system.

15. Perform the PAR Chassis Dynamometer Test. [This test includes measurement of fuel temperature, fuel API, fuel rate, inlet manifold air temperature, and barometer to correct WHP (wheel horsepower) to standard conditions]. See "Performance Analysis Report (PAR) Chassis Dynamometer Test" in this publication.

Low Power/Poor Fuel Consumption Troubleshooting Without A Dynamometer

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

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 the "Programming 3176 Parameters" section in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

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 futher details).

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 445 kPa (65 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 or damage. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR5107.* Excessive fuel return to the tank due to a malfunction of the fuel pressure regulating valve in the siphon block.

10. Check fuel injection timing. Refer to Engine Test Procedure Number P-221 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. Check the actual versus desired timing.

11. Use the ECAP and the 7X1201 Timing Adapter to monitor the injection signal duration. The duration bars should remain close in length.

NOTE: Leave the 7X1201 Timing Adapter installed for remainder of testing to monitor injection duration under all conditions.

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

A. 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".

B. Start the engine.

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. The injection signal duration for the firing cylinders should increase slightly to make up for the cutout cylinder.* If a cylinder(s) is determined to be performing improperly, refer to Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112 or Mechanical Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5113 for further diagnostics.* If no problems are found during cylinder cutout, proceed to step 13.

13. Verify fuel position (rack) using the steps that follow:

A. Lug engine in full load condition to problem rpm.

C. If the fuel position is limited to FRC fuel position, check the transducer (boost) module and supply lines for correct operation.

14. 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. See "Engine Performance Load Test (No Dynamometer)" in this publication.

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 Dynamometer test:

NOTE: Some troubleshooting steps may have been completed in a previous procedure.

1. Check the fuel API. 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.

If fuel transfer pump pressure at rated engine rpm is below 445 kPa (65 psi), check for:

*Restrictions in the low pressure fuel system (plugged fuel filter, collapsed hoses, etc).*Air in the fuel.*Fuel transfer pump wear or damage. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR5107.*Excessive fuel return to the tank due to a malfunction of the fuel pressure regulating valve in the siphon block.

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-221 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

9. Check fuel position (actual) versus rated fuel position and FRC fuel position on the ECAP status screen.

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

11. Evaluate the corrected wheel horsepower 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 setting) and FTS (full torque setting) values set to specification.

Evaluation Of The PAR Chassis Dynamometer Test Results

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

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

B. 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).

2. High fuel rate and high WHP.

A. 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.

B. Check unit injector part number to verify correct injector.

C. 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 affected 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 throttle conditions more fuel is consumed but more work is performed. Also, 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.

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

A. Inspect the air induction/exhaust system for the following:

*Boost/exhaust leaks.*Inlet/exhaust restrictions.*Aftercooler restrictions.

B. Check fuel injection timing. Refer to Engine Test Procedure Number P-221 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. Check the actual versus desired timing.

C. 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.

4. Low fuel rate, boost, and WHP.

A. Inspect the air induction/exhaust system for the following:

*Boost/exhaust leaks.*Inlet/exhaust restrictions.*Aftercooler restrictions.

B. Install an ECAP. Refer to the "3176 Electronic Service Tools" in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. Check for diagnostic codes.

If a fault is found, refer to the "Troubleshooting Diagnostic Codes" section in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112 for further diagnostics.

C. Verify fuel position (rack) using the steps that follow:

a. Lug engine in full load condition to problem rpm.

b. Use an ECAP or DDT (status screen) to compare fuel position (rack) with rated fuel position and FRC fuel position. Fuel position (rack) is limited by FRC fuel position until boost is sufficient. Once sufficient boost is available, fuel position (rack) is limited by rated fuel position. Under full throttle/load the fuel position should closely follow rated fuel position.

c. If the fuel position is limited to FRC fuel position, check the transducer (boost) module and supply lines for correct operation.

d. If the fuel position is not limited by FRC fuel position and the fuel position is less than rated fuel position, check throttle position sensor operation and adjustment. Refer to Engine Test Procedure Number P-211 and P-303 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

D. Use an ECAP or DDT (interactive diagnostics) to turn off one cylinder at a time using the steps that follow:

a. 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".

b. Start the engine.

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. The injection signal duration for the firing cylinders should increase slightly to make up for the cutout cylinder.*If a cylinder(s) is determined to be performing improperly, refer to Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112 or Mechanical Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5113 for further diagnostics.*If no problems are found during cylinder cutout, proceed to step E.

E. 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.

If the fuel transfer pump pressure is below 445 kPa (65 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 or damage. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR5107.*Excessive fuel return to the tank due to a malfunction of the fuel pressure regulating valve in the siphon block.

F. Check the unit injector part number to verify correct injector.

G. Test unit injectors for possible low fuel flow due to plugged orifices. Also examine injectors for indication of combustion leakage. Inadequate injector cone to cylinder head sleeve sealing may allow combustion gas to enter fuel system.

Engine Performance Load Test (No Dynamometer)

Required Equipment For Test:

Optional Equipment:

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

NOTE: Some troubleshooting steps may have been completed in a previous procedure.

1. Check the fuel API. 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.

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-221 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

11. Check fuel position (actual) versus rated fuel position and FRC fuel position on the ECAP status screen.

12. Evaluate the fuel position, 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 setting) and FTS (full torque setting) values set to specification.

Evaluation Of Load Test (No Dynamometer)

1. Acceptable boost, fuel position, and perceived horsepower.

A. Vehicle performance is acceptable and not a contributor to any lack of vehicle performance.

B. Further investigation may be necessary by performing a PAR Chassis Dynamometer Test. See "Performance Analysis Report (PAR) Chassis Dynamometer Test" section in this publication.

2. Acceptable boost, fuel position, and low perceived horsepower.

A. Operating conditions may be creating a loss of vehicle performance. One or more of the following conditions must exist:

B. Further investigation may be necessary by performing a PAR Chassis Dynamometer Test. See "Performance Analysis Report (PAR) Chassis Dynamometer Test" section in this publication.

3. Low perceived horsepower, low boost or improper injection timing.

A. Inspect the air induction/exhaust system for the following:

*Boost/exhaust leaks.*Inlet/exhaust restrictions.*Aftercooler restrictions.

B. Check fuel injection timing. Refer to Engine Test Procedure Number P-221 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. Check the actual versus desired timing.

D. Install an ECAP. Refer to the "3176 Electronic Service Tools" section in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. Check for diagnostic codes.

If a fault is found, refer to the "Troubleshooting Diagnostic Codes" section in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112 for further diagnostics.

E. Verify fuel position (rack) using the steps that follow:

a. Lug engine in full load condition to problem rpm.

c. If the fuel position is limited to FRC fuel position, check the transducer (boost) module and supply lines for correct operation.

F. Use an ECAP or DDT (interactive diagnostics) to turn off one cylinder at a time using the steps that follow:

a. 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".

b. Start the engine.

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. SENR5112 or Mechanical Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5113 for further diagnostics.*If no problems are found during cylinder cutout, proceed to step G.

G. 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. Special Instruction, Form No. SEHS8907 is with the tool group and gives information for its use.

If the fuel transfer pump pressure is below 445 kPa (65 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 or damage. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR5107.*Excessive fuel return to the tank due to a malfunction of the fuel pressure regulating valve in the siphon block.

H. Check the unit injector part number to verify correct injector.

I. Test unit injectors for possible low fuel flow due to plugged orifices. Also examine injectors for indication of combustion leakage. Inadequate injector cone to cylinder head sleeve sealing may allow combustion gas to enter fuel system.