New High Quality Diesel Injector 326-4700 326-4740 326-4756 282-0490 292-3780 306-9380 For CAT C4.2 C6.4 C4.4 C6.6

Preliminary judgment based on the fault phenomenon
1. Difficulty in starting or failure to start
Pressure is too low: The fuel cannot form effective spray droplets, resulting in too lean mixture in the cylinder (gasoline engine) or insufficient compression temperature (diesel engine), which is manifested as the motor turning but not starting when starting, or multiple ignitions are required.
Pressure is too high: The common rail system has difficulty in relieving pressure, which may cause excessive fuel injection at start-up (diesel engine "flooding"), and black smoke after starting.
2. Insufficient power and abnormal jitter
Pressure fluctuation: intermittent jamming of the injector or drift of the pressure sensor signal, resulting in poor operation of individual cylinders, engine idle jitter, weak acceleration, and even "missing cylinder" misfire (black or blue smoke from the exhaust pipe).
Continuous high pressure: Excessive combustion temperature causes knocking (gasoline engine knocking sound), and power output is periodically attenuated; diesel engines may cause a sudden drop in torque due to pre-ignition.
3. Abnormal exhaust and sudden change in fuel consumption
Pressure is too low: poor fuel atomization → incomplete combustion → exhaust emits black smoke (surge in diesel engine carbon soot PM), white smoke (unburned fuel vapor), and fuel consumption increases by 10%~30%.
Pressure is too high: combustion efficiency decreases → NOx emissions increase (pungent smell of exhaust gas), gasoline engines may overheat the three-way catalytic converter due to excessively rich mixture, and fuel consumption increases abnormally.
4. Abnormal noise and leakage signs
Mechanical abnormal noise:
When the pressure is too high, the "click" opening and closing sound of the injector becomes brittle and the frequency increases (the normal working frequency is about 50~200Hz, and it can reach more than 300Hz when abnormal);
The oil pump emits a "buzzing" abnormal sound or metal friction sound due to overload.
Fuel leakage:
Low-pressure pipelines (such as fuel filter interfaces) or high-pressure components (common rail pipes, injector seals) leak oil, and a clear gasoline smell can be smelled (diesel smell for diesel engines), and leakage in high-temperature areas may be accompanied by smoke.

Use professional tools for accurate detection
1. Fuel pressure gauge to measure system pressure
Operation steps:
Connect the fuel pressure gauge of the corresponding vehicle model (the high-pressure gauge needs to match the common rail system pressure, such as diesel engines can reach more than 1600bar);
Measure the pressure values ​​of the three working conditions of idling, acceleration, and pressure maintenance after shutdown:
Idle working condition:
Gasoline engine low-pressure system: 3~5bar (manifold injection), direct injection system 40~100bar (may be higher during cold start);
Diesel engine common rail system: 200~1200bar (depending on the vehicle model and load).
Sudden acceleration working condition: The pressure should rise by 10%~20% instantly (the oil pump responds normally). If it does not change or drops, it means that the pump pressure is insufficient.
Pressure maintenance after shutdown: After turning off the engine, the system pressure should be maintained at no less than 70% of the initial value within 10 minutes. If it drops rapidly, there is a leak (the injector needle valve is poorly sealed or the oil pump check valve fails).
Abnormal judgment:
If the measured value exceeds the range specified in the vehicle model manual (such as the standard value ±10%), or the pressure drop in the pressure holding test is too fast, the pressure can be judged to be abnormal.
2. Oscilloscope analysis of injector waveform
Operation points:
Connect the oscilloscope to the injector control line and read the drive voltage waveform or current waveform (different vehicle models have different drive methods, such as voltage drive, current drive, piezoelectric, etc.).
Comparison of key parameters:
Waveform characteristics Normal state Abnormal pressure may manifest
Opening delay time 0.5~1.2ms (varies with oil temperature and speed) Too long (low pressure causes slow opening of the needle valve)
Peak current 8~15A (current driven type) Abnormal fluctuation (unstable pressure causes armature jamming)
Maintain voltage/current 2~5A (maintain needle valve opening) Continuous high current (needle valve cannot be fully opened)
Close oscillation Attenuated oscillation (calms down within 10~20μs) Oscillation period is extended (pressure shock causes needle valve vibration)
3. Cylinder pressure gauge assists in judging combustion efficiency
Principle: Injection pressure directly affects the formation of the mixture, thereby changing the cylinder pressure peak.
Test method:
The spark plugs of gasoline engines need to be removed, the injectors of diesel engines need to be removed, and a cylinder pressure gauge needs to be installed;
Start the motor to measure the compression pressure (the throttle needs to be fully open):
Normal cylinder pressure of gasoline engines: 8~12bar (turbocharged models can reach 15bar);
Normal cylinder pressure of diesel engines: 30~50bar (related to the compression ratio).
Abnormal characteristics:
Low pressure cylinder: Insufficient injection pressure causes combustion lag, and the cylinder pressure peak is more than 20% lower than the normal value;
High pressure cylinder: Pre-ignition or detonation causes the cylinder pressure peak to be 15% higher than the normal value, and the pressure difference of each cylinder exceeds 10% (normal should be ≤5%).

Read ECU data stream and fault code
1. The diagnostic instrument reads real-time data
Key monitoring items:
Common rail pressure actual value vs target value:
Under normal circumstances, the deviation between the two should be less than 5%. If the actual value is continuously lower than the target value (e.g. the diesel engine target is 1000bar, but the actual value is only 800bar), it may be due to oil pump wear or pressure regulating valve failure; if the actual value is higher than the target value, it may be due to pressure sensor failure or pressure regulating valve jamming.
Injection pulse width and rail pressure correction value:
If the injection pulse width increases abnormally (e.g. the idle pulse width of the gasoline engine is greater than 3ms) and the rail pressure correction value is negative (ECU tries to reduce the pressure), it indicates that the pressure is too high; on the contrary, the pulse width exceeds the limit and still cannot meet the load demand, indicating that the pressure is insufficient.
Correlation between oil temperature and oil pressure:
For every 10℃ increase in fuel temperature, the oil pressure should drop by about 3%~5% (fuel expansion effect). If the oil temperature is normal but the oil pressure drops suddenly, it may be due to the blockage of the oil pump suction port or the failure of the filter.
2. Fault code identification
Common fault code examples:
Fault code (P code) Possible cause Abnormal pressure related point
P0087 Fuel rail/system pressure is too low Low pressure fuel pump, injector leakage
P0088 Fuel rail/system pressure is too high Pressure regulating valve stuck, pressure sensor failure
P2299 Injector drive circuit voltage is too low Abnormal pressure causes needle valve resistance to increase
P2463 Diesel particulate filter (DPF) is clogged Pressure is too low → Soot emissions exceed the standard
3. Data recording and road test analysis
Use the diagnostic instrument to record the rail pressure fluctuation curve during acceleration/deceleration:
Normal vehicle rail pressure should change linearly with load (e.g. rail pressure jumps from 800 bar to 1600 bar during rapid acceleration, which takes less than 0.5 seconds);
Abnormal vehicles may have rail pressure overshoot (exceeding the target value by 10%) or response delay (taking more than 1 seconds), indicating that the pressure regulating module (PCM) or actuator (such as the oil pump solenoid valve) is faulty.

Disassembly inspection and comparative test
1. Injector unit test
Inspection after ultrasonic cleaning:
Remove the injector from the engine and connect it to the injector tester (such as Bosch KT600) to perform:
Sealing test: Apply rated pressure (such as 150bar) and observe the dripping amount within 1 minute (normal ≤1 drop/minute, more than 3 drops are considered to be poorly sealed);
Spray morphology observation: Under standard pressure, the spray should be fine and dense cone-shaped, without deflection, drop-shaped oil particles or uneven fan-shaped (when the pressure is too low, the droplets are coarse, and when the pressure is too high, excessive atomization leads to "dry fog").
2. Replacement method to eliminate interference
Cross-cylinder test: swap the suspected faulty injector with the normal cylinder injector to observe whether the fault is transferred:
If the original faulty cylinder becomes normal and the new faulty cylinder is abnormal, it is confirmed that the problem is with the injector itself (such as poor pressure maintenance due to wear of the internal valve seat);
If the fault does not transfer, it is necessary to check the oil circuit (such as blockage of the high-pressure oil pipe, uneven pressure distribution of the common rail pipe) or the ECU drive signal.
3. Fuel quality and impurity analysis
Extract the fuel tank fuel or filter element to observe whether there is water, metal debris or colloid precipitation:
Excessive water content will cause the oil pump plunger to rust and cause pressure fluctuations;
Impurities block the injector spray hole (diameter is only 0.1~0.3mm), resulting in a sudden increase in local pressure or uneven injection volume.

Special inspection points for different models
1. Common rail system of diesel engine
Focus on the supply voltage (whether the 5V reference voltage is stable) and signal fluctuation of the rail pressure sensor (installed on the common rail pipe). You can disconnect the sensor plug and observe whether the ECU enters the default pressure mode (such as the default 1000bar) to determine whether the sensor is invalid.
Check the duty cycle signal of the ** fuel metering unit (IMV)**: the duty cycle is about 30%~40% at normal idling, and rises to 70%~85% during rapid acceleration. If the signal is abnormal but the pressure does not change, it indicates that the metering valve is stuck.
2. Gasoline direct injection system
Note the difference between the low-pressure oil circuit (fuel pump to high-pressure oil pump) and the high-pressure oil circuit (high-pressure oil pump to injector):
Low pressure can be measured with an ordinary fuel gauge (standard 3~5bar). If it is lower than 2bar, check the fuel tank pump or filter;
High pressure pressure requires a special pressure gauge (range ≥200bar). If it is lower than 30bar at idle, it may be caused by wear of the high-pressure oil pump plunger or abnormal camshaft drive.
3. Hybrid models
The fuel system of some hybrid models (such as Toyota THS and BYD DM-i) is linked with the motor system. It is necessary to detect the injection pressure in pure fuel mode to avoid the motor auxiliary drive covering up the real fault (such as when the high-pressure oil pump is driven by the motor, the unstable speed may cause rail pressure fluctuations).
Precautions and safety regulations
Risks of high-pressure fuel:
Before operation, be sure to disconnect the negative pole of the battery and release the system pressure (such as unscrewing the fuel tank cap and pressing the gasoline engine low-pressure oil pipe pressure relief valve) to avoid personal injury caused by high-pressure fuel injection (pressure can reach more than 100MPa and can penetrate the skin).
Anti-static measures:
Wear anti-static gloves when disassembling and assembling the injector to avoid static electricity from penetrating the injector solenoid coil (especially piezoelectric injectors are sensitive to static electricity).
Environmental requirements:
The fuel generated during the test must be collected in a special container and is prohibited from being discharged directly. Waste oil must be handled by a professional organization.