Engine no idle speed
The engine has no idle speed.
Generally, the throttle is turned off when it is placed at the idle position.
When the throttle is slightly enlarged, the speed is increased quickly and
cannot be stably operated at a low speed.
Reason
a. The governor idle spring is too
soft or broken.
b. The governor sensing element is
worn too much.
c. The plunger of the fuel
injection pump is seriously worn.
d. The temperature is too low.
e. The cylinder pressure is too
low.
Diagnosis and treatment
a. There is no idle speed at cold
start, which is generally a normal phenomenon. This is because the temperature
is too low, the viscosity of the oil is too large, the internal resistance of
the engine is increased, the spray and evaporation conditions of diesel oil
become worse, resulting in the engine can not maintain the minimum stable speed
operation, when the throttle is raised, it will turn off quickly. In this case,
the throttle can be adjusted to run at a slightly higher idle speed, and then
resume idle operation after the engine heats up.
b. If the engine has been used for
a long time, there is no idling condition, and the fuel consumption is not
normal due to insufficient power. It is generally the plunger wears too much,
and the oil leakage increases at idle speed, so that the oil supply cannot meet
the idle speed requirement; or the cylinder pressure is too low, the fuel
injection advance angle is too large, too small, resulting in poor engine
combustion conditions. As long as according to the insufficient
power treatment, the idle
condition will naturally recover.
c. If the above conditions are
normal, the idle working element of the governor should be considered for
abnormality. Check if the governor spring is broken or the governor is too worn
or the spring is too soft, so that the centrifugal force of the flying hammer
during idle operation is much greater than that of the spring tension and
reduce oil, or the maintenance personnel do not adjust properly. The fuel
injection pump assembly must be removed and the maintenance adjustments must be
repeated on the test bench.
d. When checking the governor,
first adjust it with the idle screw. If the adjustment is invalid, adjust the
pre-tension force of the idle spring. The idle spring adjusting nut can be
slightly screwed inward or a washer is placed on the spring seat to increase
the preload and increase the idle speed. If the spring is broken, it should be
replaced and then adjusted to restore the idle working performance.
Idle speed is too high
The idle speed of the engine is too
high, which shows that the engine speed is still higher than the specified
value of idle speed when the throttle is lifted.
Reason
a. The throttle lever is not
properly adjusted.
b. The throttle return spring is
too soft.
c. The idle limit block or
adjustment screw is out of adjustment.
d. The idle spring is too hard or
the preload is too large.
Diagnosis and treatment
Excessive idle speed is one of the
easiest faults to check and troubleshoot. First of all, check whether the
throttle is back to the minimum position, if not, check the throttle adjustment
and throttle return position. Adjust the throttle wire limit screw, if the throttle
still cannot return, and then check that the throttle return spring is too
soft. If it is the fuel injection pump shortly after inspection and
commissioning, it should be considered whether the idle speed adjustment is
correct, and the idle speed spring preload force adjustment is too large. If
the spring has been replaced, check whether the spring is too hard.
Idle speed is unstable
The form of idle instability of the
engine is that it is running at idle speed, fast and slow, or vibrated.
Reason
a. There is air in the oil circuit.
b. Low pressure oil supply is not
smooth.
c. The idle speed stabilizer is
improperly adjusted.
d. The fuel supply of the injection
pump is uneven.
e. The pin shaft and fork head of
each connecting rod of the governor are excessively worn.
Diagnosis and treatment
When the diagnosis of idle speed is
unstable, it should be analyzed and judged according to the engine service time
and maintenance degree.
a. First of all, it should be
checked whether the oil supply of the low-pressure oil circuit is unblocked,
whether the filling of the diesel oil meets the requirements, the maintenance
of the generator engine is timely, otherwise it should be cleaned, maintained
or replaced.
b. If the diesel
generator stops for a long time or the fuel tank diesel oil is
not replenished in time, a small amount of air seeps into the oil circuit and
should be exhausted.
c. If the genset has been used for
a long time, the fuel injection pump has been debugged many times without
checking the wear of the governor. During the commissioning, pay attention to
whether there is excessive wear at the joints of the speed control element and
the throttle lever. Otherwise, it should be replaced or welded. When welding
the rotating parts, attention should be paid to the symmetry of the mass to
ensure balance.
d. Idling speed is unstable and
accompanied by vibration. It is caused by the uneven oil supply of the fuel
injection pump. It can be checked by the oil-by-cylinder method. If the broken
cylinder does not cause a change in the rotational speed, it indicates that the
cylinder oil supply is insufficient or the injector atomization is poor. Check
the injector first and check the fuel injection pump.
e. If the idle speed
stabilizer is improperly adjusted, it should be re-examined on the test bench.