The Cummins QSK60 engine is a high-power diesel engine with a V-shaped 16 cylinder engine, a displacement of 60L, and a rated power of 1985kW. It is mainly used in mining, power, and shipping industries and is a flagship model produced by Cummins.
The exhaust smoke color of a diesel engine is an important and most intuitive condition for determining whether the engine is in good operating condition.
When the engine reaches normal temperature, the exhaust gas emitted is usually colorless smoke.
During high-speed and high load operation, the exhaust smoke color may be slightly gray.
If black, blue, or white smoke is emitted, it indicates that the engine has an abnormal exhaust fault.
1, The exhaust emits black smoke
The emission of black smoke from exhaust is a phenomenon in which small particles generated by incomplete combustion of diesel are discharged with the exhaust gas.
Upon discovering abnormal exhaust emissions from the QSK60 engine, the following aspects should be taken into consideration for inspection.
1. Check the quality of diesel fuel
Poor diesel quality or incorrect brand is the first reason to consider when judging engine exhaust abnormal faults.
Due to the use of PT fuel injection system in QSK60 engine, the injector aperture is small and the precision is high, which requires strict requirements for diesel quality and grade.
Considering the very stable diesel supply within mining enterprises, all equipment is refueled with diesel at fixed refueling points or dedicated refueling trucks. If the engine exhaust is abnormal due to diesel quality issues, multiple devices will experience similar failures simultaneously.
2. Check the air filter element
Blockage or dirt in the air filter can cause poor engine suction. If the exhaust is normal during idle operation and there are no other abnormal phenomena, and the exhaust is abnormal only during high load operation, the first consideration is usually whether there is a problem with the air filter.
Remove the air filter to check for dirt and blockage, and replace or clean it as appropriate.
QSK60 is equipped with a primary air filter and a safety air filter. If the dirt is not severe, it can be cleaned with compressed air and replaced with a new filter element if necessary. At the same time, the dust collection cup should be cleaned.
3. Check the intake pipeline
Air leakage in the intake pipe can cause insufficient intake of air into the engine and also lead to abnormal exhaust failure.
The QSK60 engine adopts a bipolar turbocharging and secondary intercooler intake system, with 8 turbochargers and 6 intercoolers installed. The intake pipeline layout is complex and there are many connections.
Check the rubber sleeve at the pipeline connection for aging, cracking or other damages, check if the rubber sleeve clamp is loose, check if the sensor or plug on the intercooler cross pipe is loose, check if the intercooler housing is cracked, if the installation bolts are loose, if the sealing gasket is damaged, and if there are any foreign objects blocking or damaging the interior.
If there is a leak in the intake pipe, the engine will usually produce a sharp whistling sound when running under load.
4. Check the turbocharging system
Poor operation of the turbocharger can lead to insufficient intake air, resulting in the engine emitting black smoke.
Install 4 low-pressure turbochargers and 4 high-pressure turbochargers on the QSK60 engine. Check for cracked turbocharger casings and damaged impellers, and replace or repair damaged turbochargers.
Check if there is any leakage in the exhaust manifold. Leakage in the exhaust manifold can cause poor turbo drive.
The phenomenon of bolt breakage in the exhaust manifold of QSK60 engine is quite frequent. It is necessary to carefully inspect and replace the broken exhaust manifold bolts and sealing steel gaskets in a timely manner during maintenance work.
5. Check the valve mechanism
Check the valve spring and valve seal. Damage to the valve spring and deformation or wear of the valve seal will cause the valve seal to be loose, leading to a decrease in cylinder pressure.
Check the valve clearance, which directly affects the valve timing and can cause abnormal intake and exhaust volumes in the combustion chamber, leading to an imbalance in the air-fuel mixture ratio and resulting in black smoke emissions.
A specialized plug gauge is required to check the valve clearance.
The maximum clearance of the exhaust valve of QSK60 engine is 0.81mm, and the maximum clearance of the intake valve is 0.36mm [4].
The valve clearance must be checked regularly, and the recommended inspection interval for QSK60 engines is 10000 hours.
Incorrect valve clearance may also be accompanied by low horsepower, difficulty starting, and even strong metal impact sounds in the valve train.
6. Check the compression pressure of the cylinder
When the cylinder liner and piston components are severely worn, the cylinder seal may not be tight, leading to a decrease in cylinder compression pressure and even oil entering the combustion chamber, resulting in incomplete fuel combustion and black smoke emissions.
This fault is usually accompanied by engine oil burning, blue smoke, increased waste pressure in the crankcase, decreased power, and even automatic shutdown.
Special cylinder pressure detection tools can be used to measure cylinder compression pressure, single cylinder detection, cylinder by cylinder.
Inject compressed air into the cylinder through the air valve installed on the injector hole, observe the pressure relief speed and compare it with the standard value to determine if the pressure is too low.
If the pressure relief time of a cylinder is significantly lower than the standard value or other cylinders, it can be concluded that the cylinder liner or piston components of that cylinder have been severely worn.
In addition, loose valve closure and damaged cylinder gasket can also lead to a decrease in cylinder compression pressure and the emission of black smoke.
7. Check the fuel system
The fuel system of QSK60 engine is controlled by Quantum electronic system based on HPI (High Pressure Injection).
The system receives signals from various sensors, analyzes and processes them through the ECM (Electronic Control Module), and sends control commands to the actuators, thereby achieving precise control over the injection, timing, fuel quantity, and pressure of the engine fuel.
1) Abnormal fuel control system may lead to excessive fuel supply, abnormal fuel injection timing or injection pressure in the engine.
Excessive fuel injection can cause excessive diesel to enter the combustion chamber and fail to burn completely, resulting in black smoke.
Abnormal fuel injection timing, premature injection of fuel into the combustion chamber increases the amount of premixed fuel, while late injection of fuel into the combustion chamber causes a large amount of fuel to be discharged before combustion, both of which can lead to black smoke emission.
Abnormal injection pressure will affect the injection timing. A lower injection pressure will cause the injection to start earlier, while a higher injection pressure will delay the injection time, resulting in black smoke.
Abnormal fuel control system can also cause engine power shortage, increased fuel consumption, and even difficulty starting.
Check the fuel control system by first reading the fault code through the system control software to determine the scope of the fault.
Check if the ECM calibration value is consistent with the rated value, and recalibrate if there is a difference.
Measure the signals at each terminal of the ECM. If there is no signal or the signal voltage exceeds the limit value, it can be determined that the ECM module is damaged.
Remove the actuator to check for dirt and clean if necessary.
Check the resistance between the pins of the actuator. If the resistance value does not meet the technical specifications, it can be determined that the actuator has a fault [5].
2) The fuel injected into the cylinder must be thoroughly atomized and mixed with the air inside the cylinder.
Damaged fuel injectors can cause poor fuel atomization or even direct dripping into the cylinder, resulting in incomplete fuel combustion and black smoke emissions.
Use Cense to diagnose the temperature of each cylinder and replace the fuel injector in the cylinder with abnormal temperature.
QSK60 engine injector "O" ring, head sealing copper
Pad damage and carbon deposition are common phenomena.
2, Blue smoke emitted from the exhaust
Blue smoke emitted from exhaust refers to the combustion of engine oil entering the cylinder, generating blue smoke and being discharged, commonly known as "burning engine oil".
It is normal for a small amount of engine oil to participate in combustion. The QSK60 engine integrates the Centinel oil management system, which allows a small amount of engine oil to participate in combustion.
If excessive engine oil participates in combustion and the exhaust pipe continuously emits blue smoke, it indicates that there is a malfunction in the engine.
The troubleshooting of QSK60 engine emitting blue smoke mainly starts from the following aspects.
1. Check the oil level
When the oil level in the oil pan is too high, the oil will splash onto the inner wall of the cylinder with the high-speed crankshaft and enter the combustion chamber with the reciprocating piston to participate in combustion.
Simply having a high oil level can cause blue smoke. Due to the involvement of engine oil in combustion, a large amount of heat is generated, which increases the engine power and is not controlled by the fuel control system, resulting in an increase in engine idle speed.
The correct oil level for the QSK60 engine should be between the "H" mark and the "L" mark on the dipstick.
Stop the engine for 5-10 minutes to allow the oil in the upper parts of the engine to fully flow back.
Check the oil level gauge. If the oil level is above "H", excess oil should be drained.
At the same time, the oil condition in the Centinel oil management system oil reserve tank should be checked.
If the oil level in the engine is high and the oil level in the oil replenishment tank is low, it indicates that there is a problem with the automatic oil replenishment system and it should be repaired.
2. Check the valve guide rod
Failure of the valve guide oil seal or excessive clearance between the valve guide and valve stem can cause a large amount of oil to be drawn into the intake rocker chamber and participate in combustion in the cylinder.
Open the rocker arm chamber cover, check the oil seal on the upper end of the valve guide and the gap between the guide and the valve stem, and replace worn or failed parts.
3. Check the cylinder barrel and piston components
Piston ring alignment, reverse installation, wear, breakage, cylinder pulling, and excessive clearance between piston and cylinder wear can all cause poor sealing between the piston ring and cylinder, resulting in a large amount of oil being sucked into the cylinder to participate in combustion and emit blue smoke, accompanied by a decrease in engine power, high waste pressure in the crankcase, and serious carbon or oil accumulation in the fuel injector.
Check the air pressure of each cylinder, conduct a pressure test on each cylinder, and check if the air pressure holding time is sufficient.
If the engine has just undergone major repairs, there is a higher possibility of the piston rings aligning or being installed incorrectly.
Each piston of the QSK60 engine is equipped with three piston rings, namely the top ring, middle ring, and oil ring. During assembly, their openings should be staggered at a certain angle to avoid being in the same straight line. It is recommended to stagger them by 120 °.
The piston replacement is marked with the part number, which must face the top of the piston during installation.
Check for any vertical scratches or polishing on the inner wall of the cylinder by turning the piston disc to the top dead center.
If there are scratches or more than 20% of the piston ring stroke area is polished, the cylinder barrel must be replaced.
If there is a piston ring fracture or more serious damage, metal debris is usually visible in the oil pan.
4. Check the turbocharger
Damage to the turbocharger can also cause blue smoke from the engine exhaust.
A turbocharger consists of two parts: a compressor and a turbine. Failure of the compressor rotor oil seal can cause oil to enter the intake duct and participate in combustion.
If the turbine is damaged and leaks oil, the engine oil will be vaporized by high-temperature exhaust gas, generating blue smoke that is discharged from the exhaust pipe. If the turbocharger leaks oil, it can be discovered by disassembling the intake pipe.
3, Exhaust emits white smoke
The basic reason for the emission of white smoke from diesel engine exhaust is that there is moisture in the fuel system that is heated and turned into white water vapor, which is discharged with the exhaust gas, or some unburned fuel that becomes gray white smoke (oil vapor) is discharged with the exhaust gas.
1. There is moisture in the fuel system
There are two situations where there is moisture in the fuel system:
① Excessive water content in fuel;
② The coolant enters the combustion chamber.
When there is moisture in the fuel system, the palm near the exhaust pipe will feel noticeably damp [7].
1) When the fuel quality is poor and the water content is too high, the water is vaporized into steam at high temperature in the cylinder and emitted as white smoke with the exhaust gas.
Remove the oil-water separator and check if there is a large amount of moisture, which indicates poor diesel quality.
First, drain the water in the oil circuit, and then drain the water in the fuel tank and fuel filter through the drain valve.
2) Cracks or sand holes in the cylinder head or cylinder barrel, damaged cylinder gaskets, or loose cylinder head bolts can cause coolant to seep into the combustion chamber, turning into white water vapor and being discharged.
Check if the coolant level has significantly decreased. When starting the engine, open the water tank cover and observe if the water surface is bubbling.
Check if the oil level has significantly increased and if there is any milky white liquid in the waste pressure pipe of the crankcase breather.
If the above phenomena exist, it indicates that the coolant has leaked into the combustion chamber.
Firstly, check if the tightness of each cylinder head bolt is sufficient.
If the cylinder head bolt is found to be loose, a special gauge or caliper should be used to measure the free length of the bolt. If the measurement result exceeds the specified maximum allowable free length, it should be discarded.
The correct tightening method for QSK60 engine cylinder head bolts is to tighten the bolts to 300 N · M (221ft lb) and then rotate them clockwise by 90 °.
If the cylinder head bolts are not loose or the fault is not resolved after tightening, it is necessary to apply pressure to the inside of the water tank to further determine the location of the leakage. The pressure of the QSK60 engine water tank should not exceed 140kPa (20PSI).
Drain the engine oil and remove the oil pan to observe the water leakage.
After identifying the leaking area, open the corresponding cylinder head, check for damage to the cylinder head, cylinder head gasket, cylinder barrel, etc., and replace any damaged parts.
2. Poor fuel combustion
1) The ambient temperature or engine temperature is too low, causing some fuel to fail to burn and turn into oil vapor, which is discharged from the exhaust pipe.
The QSK60 engine is equipped with a preheating device. First, check if the preheating device is working properly.
If the preheating device works normally and the white smoke gradually disappears with the increase of engine temperature, it is a normal phenomenon and does not need to be further ruled out.
2) If the preheating device is working properly and the symptom of white smoke still persists as the engine temperature increases, it is necessary to check whether the fuel injection timing is correct.
Late fuel injection results in poor mixing of oil and gas, leading to the formation of a large amount of water vapor and smoke during combustion.
3) If the white smoke gradually turns into black smoke as the engine temperature increases, it is necessary to check the fuel injectors of each cylinder.
If the fuel injector has poor atomization or even drips oil, it will result in incorrect fuel air mixture ratio, leading to incomplete fuel combustion and easy formation of water vapor and smoke.
If none of the above methods eliminate the fault, the fault should be caused by insufficient cylinder compression pressure.
Check the pressure of each cylinder and repair the cylinders with significant pressure differences.
Cylinder wear, deformation or breakage of piston ring components, or poor valve sealing can all lead to insufficient cylinder pressure.
The specific inspection methods for fuel injectors and cylinder pressure can refer to the previous section on exhaust black smoke faults.
4, Conclusion
Abnormal exhaust is a comprehensive reflection of internal engine faults, and determining whether the engine is in good working condition through exhaust conditions is one of the important means to eliminate engine faults.
If the engine exhaust fault can be dealt with in a timely manner, it can ensure the ideal operation of the engine, extend its service life, and avoid unnecessary economic losses.
