this article will guide you to know
about the common faults and troubleshooting of Cummins engine.
1. Diagnosis and treatment of
engine starting difficulty or failure to start and exhaust pipe emitting a
large amount of ash and white smoke.
The engine is difficult to start, and the exhaust pipe
discharges a large amount of gray smoke, which is diesel vapor.
Reason
a. The engine temperature is too
low, diesel oil is not easy to evaporate and burn.
b. Poor atomization of injector
c. The oil supply is too late.
d. The oil supply is too small and
the mixture is too lean.
e. Cylinder leakage is too much,
compression can not reach the ignition temperature.
Diagnosis and treatment
a. If the engine temperature is too
low in cold season, check whether the low temperature starting preheating
device fails, that is, whether the preheater control circuit has open circuit,
short circuit or preheater failure.
b. If the low temperature
preheating device is normal, check whether the injection timing is correct.
Turn the engine and insert the engine camshaft timing pin, that is, when it is
located at the upper dead center of cylinder compression, check whether the
fuel pump camshaft lock pin can be inserted. If it cannot be inserted, it
indicates that the injection timing is wrong and needs to be adjusted.
c.The spray quality of each
cylinder injector should be checked to meet the requirements.
d. If the first two items are
normal, check if the oil supply is too small. During cold start, due to the low
temperature in the cylinder, the fuel viscosity is large, and the evaporation
condition is poor, the starting oil supply is required to be larger than the
rated oil supply.
e. Finally check the cylinder
pressure and repair it when the pressure difference is very far.
2. Diagnosis and treatment of
engine starting difficulty or failure to start and exhaust pipe emitting a lot
of black smoke.
The engine is difficult to start,
and the exhaust pipe emits a large amount of black smoke, which is the result
of incomplete combustion of the diesel oil.
Reason
a. Diesel oil is of poor quality.
b. The air intake is not smooth and
the air filter is blocked.
c. The injection timing adjustment
is too early.
d. Injector needle valve sealing is
poor, there is dripping oil leakage phenomenon.
e. The injection pressure is too
low
f. The fuel supply of the fuel
injection pump is too large and the combustion is deteriorated.
g. Low cylinder pressure and poor
atomization.
Diagnosis and treatment
a. Determine if the diesel quality
meets the requirements.
b. Check if the air filter is
clogged.
c. Check if the injection timing is
too early. Turn the engine and insert the engine camshaft timing pin, that is,
when it is located at the upper dead center of cylinder compression, check
whether the fuel pump camshaft lock pin can be inserted. If it cannot be
inserted, the fuel injection timing is wrong and needs to be adjusted.
d. Check whether the fuel pump
supply is too large.
e. Check if the fuel injection
pressure and spray condition of the fuel injector are good, and the fuel
injector should not have a dripping phenomenon.
f. The working condition of each
cylinder shall be checked by the oil-breaking method.
g. If the above inspection is
normal, but the fault remains, check whether the cylinder pressure and piston,
piston ring and cylinder clearance are abnormal, whether the cylinder gasket is
damaged or the valve is not tightly closed, etc.
3. Diagnosis and treatment of
engine thermal starting difficulties
The cold start of the engine is
good, but after running for a period of, temperature rises and the engine turns
off. It is difficult to start again.
Reason
It is mainly caused by serious wear
of plunger pair of fuel injection pump and needle valve pair of fuel injector.
When the hot car starts, the fuel viscosity is reduced due to the high
temperature of the fuel injection pump and fuel filter, and the starting speed
is low, and most of the diesel oil leaks from the worn gap, resulting in
insufficient starting oil and unable to start.
Diagnosis and treatment
a. The method of emergency
elimination is: the car is hung up and driven by other cars. Using the speed of
the car to drive the high-speed rotation of the engine, so that the diesel can
not leak, to ensure the starting fuel supply (this method is not recommended,
because the cylinder pressure of Cummins supercharged engine is relatively
large, the impact force on the connecting parts when the trailer starts is
large, affecting the vehicle service life).
b. When the plunger pair or needle
valve pair is seriously worn, the new product should be replaced after the
inspection and debugging of the fuel injection pump test bench.
4. Diagnosis and treatment of
engine with normal low speed and short time high speed with too little smoke
exhaust
The engine idle speed is good, and
the throttle speed can be increased rapidly. However, the continuous boom
throttle speed is not easy to rise, the driving is weak, or the medium speed is
not able to drive. This is caused by insufficient low pressure oil supply.
Reason
a. Fuel filter or the oil-water
separator is blocked.
b. Low pressure oil circuit is not
smooth.
c. Insufficient oil supply in oil
pump or the oil filter is blocked.
d. The inlet valve of fuel tank
cover is invalid.
All of the above conditions can
cause the fuel pressure of the low pressure oil chamber of the fuel injection
pump to be insufficient, and only the oil supply amount required for the small
load can be maintained. when It is necessary to use more oil supply for large
and medium load, it cannot be satisfied, resulting in a weak driving.
Diagnosis and treatment
a. Check whether the intake valve
of the tank cover is invalid, if it fails, a certain vacuum degree will be
formed in the tank, and the diesel oil cannot be sucked out. Most of this
phenomenon is caused by the loss of fuel tank cover and sealing with airtight
plastic cloth.
b. Check if there is any concavity
in the low pressure oil pipe and whether there is any blockage at the inlet
pipe joint filter.
c. If the fuel filter or oil-water
separator is not replaced for a long time, it should be replaced in time.
d. Check if the oil pump is working
properly. If the oil supply is insufficient, replace or repair the oil pump in
time.
5. Diagnosis and repair of low
engine speed but no high speed, too little smoke exhaust
The low speed of the engine is
good, but the speed can not be increased at the time of acceleration, and the
driving is weak, which is caused by insufficient circulating oil supply.
Reason
a. The fuel injection pump is not
adjusted properly, so that the fuel supply is reduced.
b. The governor spring is reduced
in elasticity due to fatigue. When the throttle is stepped to the end, the oil
adjustment lever can not move forward to the head, so that the fuel supply of the
fuel injection pump is reduced and the engine cannot reach the rated speed.
c. The fuel pump plunger and the
sleeve, the injector needle valve and the needle valve body are seriously worn,
so that the diesel oil leakage increases when the oil is pumped, and the oil
supply amount is relatively reduced.
d. Improper adjustment of the
throttle control lever, or the accelerator pedal pin is too far, the
accelerator pedal cannot be placed in place, resulting in too little oil supply
at full load.
e. There is air in the oil circuit
Diagnosis and treatment
When the engine power is insufficient,
if the low speed is good and the smoke exhaust is normal, it means that the
engine burns well, that is, the diesel injection quality is good, the fuel
supply start time is normal, the cylinder sealing is good and the intake air is
sufficient.
a. In the case of normal
low-pressure oil circuit, first check whether the degree of looseness of the
accelerator pedal connecting pin and the length adjustment of the connecting
rod are properly adjusted. When the throttle is stepped to the end and the governor
arm is at the maximum position, the high speed limit screw should be in contact
with the limit block. Otherwise it should be adjusted.
b. Drain the air from the oil
circuit.
c. Debug the fuel injection pump on the test bench to
eliminate the fault.
In the previous:4. Reasons and Solutions for Common Faults of Cummins Diesel Engine
The next article:2. Diagnosis and Treatment of Cummins Engine Power Shortage