New High Quality Diesel Injector 386-1766 20R-1275 386-1767 20R-1276 386-1768 20R-1277 386-1769 20R-1278 For CAT C3500B

Fault phenomenon of too low pressure
1. The engine is difficult to start or cannot start
Principle: Insufficient injection pressure leads to poor fuel atomization, and the mixture is too lean or difficult to be compressed and ignited.
Performance:
The starter operates normally at startup, but there is no explosion sound in the cylinder and no obvious exhaust smoke from the exhaust pipe.
It is particularly obvious in low temperature environment (due to poor fuel evaporation conditions).
2. Insufficient power and weak acceleration
Principle: Poor fuel atomization leads to slower combustion speed, reduced effective expansion work, and reduced engine power.
Performance:
The vehicle has obvious lack of power when climbing a slope or overloading, and the acceleration is slow even when the accelerator pedal is pressed to the bottom.
The maximum speed is lower than the rated value when driving at high speed (such as the rated speed of 120km/h, the actual speed can only reach 90km/h).
3. Unstable idling or shaking
Principle: The amount of fuel injection in each cylinder is uneven (the fuel atomization of the cylinder with low pressure is poor), resulting in unbalanced combustion.
Performance:
The engine speed fluctuates >100rpm at idle (normal fluctuation is ≤50rpm), and the exhaust pipe emits a "thumping" sound.
It may be accompanied by the failure of individual cylinders (which can be discovered through cylinder disconnection test).
4. Black smoke from exhaust
Principle: Poor fuel atomization leads to incomplete combustion, and unburned carbon particles are discharged with the exhaust gas.
Performance:
Black smoke is obvious during rapid acceleration, and "ink-like" smoke is formed in severe cases.
The diesel smell is strong, and black carbon deposits are attached to the inner wall of the exhaust pipe.
5. Abnormal increase in fuel consumption
Principle: Incompletely burned fuel is discharged with exhaust gas or attached to the cylinder wall (diluting the engine oil), wasting fuel.
Performance:
The fuel consumption per 100 kilometers is 20%-30% higher than normal working conditions (such as the standard fuel consumption of 30L/100km, the actual measurement is 36L/100km).

Fault phenomenon of excessive pressure
1. Abnormal noise of engine (knocking)
Principle: Excessive pressure causes the fuel injection time to be advanced, and the peak value of combustion explosion pressure appears before the piston reaches the top dead center, generating impact load.
Performance:
A "dangdang" metal knocking sound is emitted when idling or accelerating, similar to the sound of excessive valve clearance.
The greater the load, the more obvious the abnormal noise, which may be accompanied by increased engine vibration.
2. Blue or white smoke from exhaust
Principle:
Blue smoke: Excessive pressure may cause cylinder wall oil to be sucked into the combustion chamber for combustion (such as when the piston ring is worn).
White smoke: The fuel atomization is too fine, resulting in incomplete combustion, and the unburned fuel is discharged in the form of droplets (more obvious at low temperatures).
Performance:
The exhaust pipe discharges smoke in blue or white, and the white smoke may turn colorless after the engine is heated (blue smoke continues to exist).
3. Power drops or stalls during acceleration
Principle: Excessive pressure causes the injection advance angle to be too large, and the peak value of combustion pressure is too high, resulting in increased downward resistance of the piston, and even "reverse drag" phenomenon.
Performance:
During rapid acceleration, the engine speed suddenly drops, accompanied by a body jerk, similar to the gearbox shift shock.
4. Abnormal wear or damage of the injector
Principle: The impact of high-pressure fuel on the needle valve sealing surface and valve seat increases, accelerating wear and even causing the odd parts to get stuck.
Performance:
Abnormal pressure occurs repeatedly in a short period of time (such as excessive pressure again shortly after repair).
After disassembly, it can be seen that there are obvious scratches and pits on the needle valve head or valve seat.
5. Common rail system component overload
Principle: Excessive pressure may cause the common rail pipe and high-pressure pump safety valve to open frequently, and even damage the sensor or solenoid valve.
Performance:
The common rail pressure sensor reports a fault code (such as P0191 - sensor signal is too high).
After the pressure limiting valve is opened, a large amount of fuel flows back through the return pipe, and the fuel tank temperature rises abnormally.

Fault phenomenon of pressure fluctuation
1. The speed fluctuates (wandering)
Principle: The periodic fluctuation of injection pressure causes the injection amount to fluctuate, and the engine torque fluctuates accordingly.
Symptoms:
When idling or driving at a constant speed, the tachometer pointer swings up and down (fluctuation range > 200rpm).
Similar to the "asthma" phenomenon, it may be accompanied by periodic blasting sounds from the exhaust pipe.
2. Intermittent power interruption
Principle: When the pressure drops suddenly, there is no fuel injection for a moment, resulting in loss of engine power; after the pressure is restored, the power suddenly recovers.
Symptoms:
Sudden "stall" during driving, and then returns to normal after a few seconds, which may be accompanied by vehicle shaking.
It is more likely to occur on mountain roads or when the load changes (such as insufficient pressure when climbing a slope, and pressure rises when going downhill).
3. Abnormal vibration or noise
Principle: Pressure fluctuations cause the combustion sequence of each cylinder to be disordered, and the uneven explosion pressure causes engine vibration.
Symptoms:
Periodic vibrations are transmitted from the engine compartment, and the steering wheel or pedals have obvious vibrations.
It may be accompanied by abnormal vibration of the high-pressure oil pipe (the "buzzing" sound changes with the speed).

Unique phenomena of different systems
1. Mechanical injector (non-common rail system)
When the pressure is abnormal: the fault phenomenon is usually related to a single cylinder (such as low pressure in a cylinder causing the cylinder to not work), which can be located by cylinder disconnection test.
Typical performance: When the pressure of a single cylinder is low, the exhaust temperature of the cylinder is significantly lower than that of other cylinders (temperature difference > 50°C).
2. Electronic common rail system
When the pressure is abnormal: the ECU will trigger the protection mechanism (such as limiting torque, lighting the fault light), and store the fault code.
Typical performance:
The fault light is on, and the diagnostic instrument reads codes such as P0087 (rail pressure is too low) and P0088 (rail pressure is too high).
Some models will enter "limp mode" and the maximum speed is limited to less than 2000rpm.

Extended impact of the fault
Intensified mechanical wear:
Too low pressure causes fuel to dilute the engine oil (enter the crankcase), accelerating the wear of piston rings and cylinder liners.
Excessive pressure causes the combustion temperature to rise, which may burn the valve and the top of the piston.
Excessive emissions:
Increased emissions of pollutants such as black smoke (carbon particles) and nitrogen oxides (NOx) may lead to failure of annual inspection or blockage of the post-treatment system (such as DPF).
Decrease in economy:
Fuel waste, increased oil loss, and increased maintenance costs (such as frequent replacement of injector parts).
Quick diagnosis suggestions
Preliminary investigation:
Observe the color of the exhaust gas, listen to the abnormal sound of the engine, and judge the type of abnormal pressure (too low/too high/fluctuation) in combination with the fluctuation of the tachometer.
Tool detection:
Mechanical injector: Use the injector calibrator to test the opening pressure and spray shape (normal spray should be fine cone-shaped and without dripping).
Common rail system: Use the diagnostic instrument to read the rail pressure data stream (comparison of the pressure value at idle and acceleration with the standard), and detect the high-pressure pump and pressure sensor signals.
Comparative analysis:
Multi-cylinder engines can compare the pressure data of each cylinder injector (difference > 5% is considered abnormal), and prioritize the abnormal cylinder.