Diesel engines are known for their power and torque, but they can also experience low power problems. If a diesel engine is experiencing low power output, there could be several reasons for this issue. Diagnosing and resolving the problem will require a systematic approach. Here are some common causes of low power in diesel engines:
Probable Cause(s):
1. Dirty Fuel Filters
2. Oil Level Too High
3. Restrictions And/Or Leaks In Air Inlet System
4. Plugged Or Damaged Muffler
5. Fuel Pressure Is Low
6. Low Quality Fuel Or Water In Fuel
7. Defect In Unit Injector(s)
8. Valve Adjustment Not Correct
9. Turbocharger Has Carbon Deposits Or Other Cause Of Friction
10. Air, Water, Or Gas In Fuel
11. Defect In Boost Sensor
12. Defect In Coolant Temperature Sensor
13. Defect In Throttle Position Sensor
14. Defect In Injection Actuation Pressure Sensor
1. Dirty fuel filters:
2. Oil level too high:
Remove dipstick and check oil level. If level is too high, drain oil to bring the oil level to the desired level.
NOTE: An oil sample should be run to find out if the oil level is increasing due to a fuel leak or other engine problem.
3. Restrictions and/or leaks in air inlet system:
a. Check for leaks.
b. Check the pressure in the air inlet manifold. Look for restrictions at the air cleaner. Correct any leaks.
c. Look for restrictions in the air cleaner.
d. Defect in the air-to-air aftercooler. Check temperature of inlet and outlet air from air cooler. Remove any external or internal restrictions.
4. Plugged or damaged muffler:
Vehicles equipped with catalytic mufflers, especially those that idle for long periods of time and/or operate in cooler climates, are susceptible to plugging. One indication of a plugged muffler is poor engine response. For testing procedures of mufflers, refer to the Testing And Adjusting Section, Measurement Of Pressure In Exhaust Manifold, of this Service Manual. For information concerning the replacement of the muffler refer to the Disassembly And Assembly Section of this Service Manual.
5. Fuel pressure is low:
Make sure there is fuel in the fuel tank. Look for leaks or bad bends in the fuel line between fuel tank and fuel transfer pump. Look for air in the fuel system. Make sure the fuel filters are clean, then check fuel pressure. The outlet pressure of the fuel transfer pump must be a minimum of 200 kPa (29 psi) at full load speed. If fuel pressure is lower than the above pressure, check the fuel transfer pump and fuel pressure regulating orifice at the fuel return line.
6. Low quality fuel or water in fuel:
Test the engine using fuel according to recommendations by Caterpillar Inc. Refer to Truck Performance And Driveability Diagnostic Guide, LEBT3477. Remove the fuel from the fuel tank. Install new fuel filter. Put a good grade of clean fuel in the fuel tank. Fuel API rating can be easily checked using the 1P7408 Thermo-Hydrometer. Instructions are given in Special Instruction SEHS8874.
7. Defect in unit injector(s):
Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting, SENR6566, for Injector Solenoid Circuit Test.
8. Valve adjustment not correct:
Check and make necessary adjustments as per Testing and Adjusting Section of the Service Manual.
9. Turbocharger has carbon deposits or other cause of friction:
Make inspection and repair turbocharger as necessary.
10. Air, water, or gas in fuel:
a. Check inlet line or transfer pump for air leak.
b. Check sleeve or sleeve to head joint for water leak.
c. Check unit injector seat erosion in sleeve or tip seal for combustion gas leak.
11. Defect in boost sensor:
Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting, SENR6566, for Consistent Low Power/Poor Or No Response To Throttle.
12. Defect In Coolant Temperature Sensor:
Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting, SENR6566, for Engine Sensor Open Or Short Circuit Test.
13. Defect In Throttle Position Sensor:
Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting, SENR6566, for Consistent Low Power/Poor Or No Response To Throttle.
14. Defect In Injection Actuation Pressure Sensor:
If injection actuation pressure is below desired, then the unit injectors may not be able to inject fuel. The injection Actuation Pressure Control Valve could cause this if debris is clogging the valve. Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting, SENR6566, for Injection Actuation Pressure Test.