There are two phenomena of insufficient engine power, uneven speed, and thick black smoke from the exhaust pipe:
One is continuous exhaust of black smoke; the other is intermittent exhaust of black smoke, and the engine shakes.
⑴ The reason for the lack of engine power and continuous black smoke discharge is that most or all cylinders of the engine have too much fuel supply, the ratio of fuel and air is out of balance, severe oxygen deficiency during combustion, incomplete diesel combustion, and suspended free carbon The element is formed when the exhaust gas is discharged together. If the exhaust pipe is discharging black smoke intermittently, accompanied by a “burst” sound, it indicates that the combustion of individual cylinders is not complete.
The reasons are summarized as follows:
① Improper commissioning of the fuel injection pump results in excessive fuel supply and incomplete combustion.
②The injection quality of most injectors is poor.
③ Irregular fuel supply.
④ The opening height of the intake valve is reduced and the opening time is delayed, resulting in insufficient intake.
⑤The air filter element is too dirty or the air filter is installed incorrectly, which makes the air not smooth. ⑥ The supercharging efficiency of the supercharger is reduced.
⑦ The fuel quality is too poor.
⑵Diagnosis and treatment methods When diagnosing such failures, we should start with the most obvious feature of the failure. Whether it is continuous or intermittent discharge of black smoke, this principle should be followed.
① If the engine suddenly emits black smoke, but the fault disappears naturally after a period of operation, it is mostly caused by poor fuel quality. Due to the impurity in the oil blocking the injector, the injection quality is poor, and the exhaust emits black smoke. Run for a period of time. After time, the impurities are washed away by the high-pressure oil, this kind of failure does not need to be dealt with.
②If the black smoke is exhausted continuously, consider checking whether the air intake is unobstructed, and whether the air intake pipe is deformed to increase the air intake resistance. First remove the air filter cover, take out the filter element and clean and retest the machine after maintenance, and observe whether the exhaust pipe still continues to exhaust black smoke. If the exhaust smoke is significantly reduced, it means that the air filter is too dirty or there is a problem with the installation, which has affected the air intake, and the maintenance of the air intake system should be strengthened.
③If the air flow in the intake duct is unobstructed, check whether the fuel supply time is too late. If the fuel supply is too late, the fuel entering the cylinder will be discharged before it is fully burned and form black smoke.
④The injection quality of most injectors is severely deteriorated, and the fuel atomization is poor, which cannot meet the needs of the shape of the combustion chamber, which makes the formation of combustible mixture difficult, and part of the fuel is converted into free carbon and discharged. This is also one of the causes of black smoke, so the injector should also be inspected and repaired.
⑤Check whether the fuel quality meets the standard, and use standard diesel that meets the engine’s normal operation under the ambient temperature of the area.
⑥Check whether the turbocharger is working properly. When the supercharger fails, the pressure at the end of the engine’s intake will drop, causing the temperature and pressure at the end of compression to drop, which will affect the fuel injection atomization and combustion temperature.
⑦If the maintenance time of the fuel injection pump is not long, the exhaust pipe emits black smoke, and the power is insufficient, you should consider whether the fuel injection pump is not properly debugged and the fuel supply is too much. For this reason, the fuel supply of the fuel injection pump under various working conditions should be re-calibrated. Quantity to make it meet the regulations.
⑧ If the above is normal and the engine has been running for a long time, consider checking whether the valve opening height and opening time are correct. Long-term use can cause the valve drive parts to wear out, the normal valve phase and valve lift are inaccurate, the intake air volume decreases, and the residual exhaust gas volume in the cylinder increases correspondingly, which directly affects the full combustion of fuel.
⑨For the diagnosis of uneven speed, intermittent black smoke, and engine weakness, the cylinder-by-cylinder oil-cut method can be used to check. When a cylinder is cut off, the engine speed is significantly reduced, the black smoke is reduced, and the abnormal noise disappears, which means that the cylinder has too much fuel supply, and the fuel injection volume of the cylinder should be checked and adjusted. If the engine speed changes slightly and the black smoke disappears, it means that the spray quality of the injector of this cylinder is poor, and the injector should be inspected and repaired.
If the engine speed still has no change, it means that the cylinder is not working. Check the high-pressure fuel supply of the cylinder. For example, what is the fit of the plunger pair of the fuel injection pump and the delivery valve pair, and the fixing of the fork on the oil volume adjustment lever Whether the screw (or the tightening screw of the gear ring) is loose, whether the plunger spring is broken, etc. If all are normal, check the working condition of the injector and whether the cylinder has mechanical failure.