1. Cummins engine power shortage and exhaust white smoke
Engine power shortage, exhaust pipe exhausts white smoke,
generally due to late injection time. At this time, not only the high speed
operation is poor, the acceleration is not sensitive, and the temperature is
too high.
Reason
a. Fuel injection advance angle is too small.
b. Injector is poorly atomized.
c. Engine temperature is too low.
d. There is water in the cylinder.
e. There is water in diesel oil.
Diagnosis and treatment
a. Engine power shortage, exhaust pipe exhaust white
smoke, first of all, put your hand on the muffler exhaust port, if there are
water droplets on your hand, check whether this is any moisture in the diesel
and the cylinder (according to the engine starting difficulty or can not start
and exhaust white smoke fault for maintenance).
b. When the engine is just started, it exhausts white
smoke. the cause is that the starting temperatureis too low and some of the
diesel oil volatilized into steam, which is discharged directly without
combustion. If the white smoke gradually disappears after the engine
temperature rises, it is normal. If the engine starts with white smoke, and the
black smoke appears after the temperature rises, it means that the cylinder
pressure is insufficient. Although the compression ignition condition is
improved, the diesel oil cannot be completely burned, so that the engine power
is insufficient, and the cylinder pressure should be checked and repaired.
c. Engine power is insufficient, exhaust pipe discharges
off white smoke, usually caused by too small fuel injection advance angle. If
the engine temperature is too high and the speed is slow, it can be considered
that the injection time is too late. If this phenomenon occurs suddenly, most
of the fuel injection pump shaft is rotated relative to the fuel injection pump
gear, resulting in a small injection advance angle. The timing of the injection
timing should be adjusted.
d. Finally, check the injector atomization quality and
adjust the injector.
2. Engine power shortage and
exhaust black smoke
There are two kinds of phenomenon
of engine power shortage, uneven rotation speed and exhaust pipe black smoke:
one is continuous black smoke exhaust; the other is intermittent black smoke
and the engine shakes.
Reason
Insufficient engine power and continuous
black smoke are formed by the excessive fuel supply in most or all the
cylinders of the engine, the imbalance of the mixture of fuel and air, severe
oxygen deficiency during combustion, incomplete combustion of diesel oil, and
the discharge of suspended free carbon with the exhaust gas. If the exhaust
pipe is intermittently black smoke, accompanied by a "chug" sound, it
means that the individual cylinders are not completely burned. The reasons are
as follows:
a. The fuel injection pump is not
debugged properly, resulting in excessive oil supply and incomplete combustion.
b. Most injectors have poor
injection quality.
c. Oil supply is not correct.
d. The opening height of the intake
valve is reduced and the opening time is delayed, resulting in insufficient
intake.
e. The air filter element is too
dirty or the air filter is installed incorrectly, making the air is not smooth.
f. The supercharging efficiency of
the supercharger decreases.
g. Poor fuel quality.
Diagnosis and treatment
When diagnosing such faults, it is
important to proceed from the most obvious fault characteristics, whether
continuous or intermittent black smoke, this principle should be followed.
a. If the engine suddenly emits
black smoke, but the fault naturally disappears after running for a period of
time, it is mostly caused by poor fuel quality. Because the impurities in the
oil block the injector, the injection quality is poor, and the exhaust emits
black smoke. After running for a period of time, Impurities are washed away by
high pressure oil and this type of failure is not treated.
b. If black smoke is continuously
discharged, it may be considered to check whether the intake air is
unobstructed, and whether the intake pipe is deformed increases the intake resistance.
First remove the air filter cover, take out the filter element and clean it,
then re-test the machine to see if the exhaust pipe continues to exhaust black
smoke. If the smoke exhaust is significantly reduced, it means that the air
filter is too dirty or has a problem with the installation, which affects the
intake air volume, the maintenance of the intake system should be strengthened.
c. If the air flow in the air inlet
is unobstructed, it should be checked whether the oil supply time is too late.
If the oil supply is too late, the fuel entering the cylinder will not be fully
burned and will be discharged to form black smoke.
d. The injection quality of most
injectors is seriously deteriorated, the fuel atomization is poor, can not
adapt to the needs of combustion chamber shape, resulting in the formation of
combustible mixture is difficult, and some 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.
e. Check that the fuel quality is
up to standard and use standard diesel that meets the normal operation of the
engine at ambient temperatures in the area.
f. Check that the supercharger is
working properly. When the supercharger fails, the pressure at the end of the
engine intake decreases, causing the temperature and pressure at the end of the
compression to decrease, affecting fuel injection atomization and combustion
temperature.
g. If the fuel injection pump is
not repaired for a long time, the exhaust pipe is black smoke, and the power is
insufficient, then it should be considered whether the fuel pump is improperly
debugged to make the fuel supply too much. The fuel supply of the fuel pump
under various working conditions should be recalibrated t o make it comply with
the regulations.
h. If all of the above are normal
and the engine has been running for a long time, consider checking that the
valve opening height and opening time are correct. Long-term use can cause the
valve transmission parts to wear, the normal valve phase and valve lift
misalignment, the intake air amount is reduced, and the residual exhaust gas
volume in the cylinder is correspondingly increased, which directly affects the
full combustion of the fuel.
i. For uneven speed and
intermittent exhaust of black smoke, engine weakness diagnosis can be checked
by cylinder-by-cylinder oil cut-off method.
When a cylinder is cut off, the
engine speed is significantly reduced, the black smoke is reduced, and the
abnormal noise also disappears. This indicates that the cylinder supply of oil
is too much, and the fuel injection amount of the cylinder should be checked
and adjusted. If the engine speed changes little and the black smoke
disappears, it indicates that the injector has poor spray quality, and the
injector should be inspected and repaired. If the engine speed remains
unchanged, it means that the cylinder does not work. The high pressure oil
supply condition of the cylinder should be checked. For example, the fitting
condition of the fuel pump plunger pair and the oil outlet valve pair, the fork
is fixed on the oil quantity adjusting rod. Whether the screw (or the fastening
screw of the ring gear) is loose, and the plunger spring is not broken. If it
is normal, check the working condition of the injector and whether the cylinder
has a mechanical failure.
3. Engine power shortage and exhaust blue smoke
The engine emits blue smoke at low
temperature or small load, and becomes dark gray smoke after the temperature
rises, and the power is insufficient.
Reason
When the engine is running, exhaust
pipe discharges blue smoke, because the oil enters the combustion chamber, and
when the engine is at low temperature or small load, it fails to burn and is
discharged as blue smoke. However, when the engine temperature rises or the
load increases, the oil vapor is burned and dark gray smoke appears. The
reasons for the above phenomenon are:
a. Air intake is not smooth, causing
the oil in the supercharger to be sucked into the cylinder to burn.
b. There is too much oil in the oil
sump and the oil exceeds the maximum limit.
c. Oil enters the valve guide.
d. Cylinder is heavily bleeding
oil.
e. The supercharger rotor shaft is
seriously worn and the oil retaining ring is damaged, causing the supercharger
to fail to reach the rated speed and oil leakage.
Diagnosis and treatment
a. Check that the air intake is
unblocked and check whether there is oil in the supercharger housing.
b. Take out the oil dipstick after
the engine is turned off for 5 minutes, and check whether the oil in the oil
pan exceeds the maximum limit; if it exceeds, the excess part should be
released.
c. If the above inspection is
normal, the injector can be removed, check whether the nozzle hole of the
needle valve is unobstructed. If the carbon deposit is serious or oily, the
organic oil in the cylinder is intruded.
d. Check the upper end of the valve
guide oil seal and the gap between the valve and the valve stem is too large.
Further, the cylinder head should be removed to check whether the piston ring
is stuck in the ring groove, the end gap is opposite, the fracture is weak, the
elastic force is weakened, the conical ring or the twist ring is reversed, and
the piston, the piston ring and the cylinder are worn excessively. No pull
cylinders and other phenomena, if there are abnormal conditions, timely
maintenance.
e. Whether oil leakage caused by
improper use and improper maintenance of the turbocharger rotor shaft oil seal, mixed
into fresh air into the cylinder, or vaporized by high temperature exhaust gas
when exhausted from the turbine end with the exhaust gas. If the oil
leakage should be replaced, the turbine carbon should be removed and the
bearing clearance of the rotor shaft should be checked to avoid damage to the
new oil seal.
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