Professional Manufacture 0 445 120 357 Diesel Injector Common Rail Injector Engine Parts Vehicle Parts 0445120357

The injector is the core component of the engine fuel supply system. Its spray quality, injection pressure and sealing directly affect the combustion efficiency, power output and emission performance. Functional testing needs to focus on the four core indicators of injection pressure, spray state, sealing and responsiveness. The specific methods are as follows:

Injection pressure test: verify whether the opening pressure meets the standard
The injection pressure is the lowest pressure when the injector starts to spray fuel (set by the pressure regulating spring). Too high pressure will lead to excessive atomization and increased fuel consumption; too low pressure will lead to poor atomization and incomplete combustion.
Test method:
Special injector test bench test
Install the injector on the test bench, pump oil manually or electrically, and observe the pressure gauge:
When the injector starts to spray oil, the pressure gauge pointer will "jump", and the reading at this time is the actual injection pressure;
Compare the standard value of the model (such as diesel engines are usually 180-220bar, and the high-pressure common rail system can reach 1600-2000bar). If the deviation exceeds ±5% (such as the standard 200bar, the actual measurement is lower than 190bar or higher than 210bar), it is necessary to adjust the pressure regulating screw for calibration. If it still does not meet the standard after adjustment, the injector is internally worn (such as needle valve stuck, spring fatigue), and needs to be repaired or replaced.
Simple tool test
If there is no test bench, a manual injector calibrator (with pressure gauge) can be used:
After connecting the injector, pump oil slowly, record the pressure value at the moment of injection, and determine whether it is within the standard range.

Spray state test: Check atomization quality and injection angle
The injector needs to atomize the fuel into uniform and fine oil droplets and spray it into the combustion chamber at a specific angle (such as 15°, 30°, 60°) to ensure full mixing with the air.
Test method:
Static spray observation
Trigger the injector to spray on the test bench and observe with the naked eye or a high-speed camera:
Atomization quality: Normal spray should be a uniform "conical" or "umbrella-shaped" oil mist, without obvious oil beams, oil droplets or "flying oil" (local coarse oil particles splashing); if "columnar oil flow" or "intermittent spray" appears, it means that the needle valve is worn or the spray hole is blocked.
Injection angle: Use a special angle ruler to measure the angle of the spray edge. The deviation from the standard angle should be ≤3° (such as the standard 25°, the actual measurement of 22° or 28° is abnormal). Excessive angle deviation will lead to uneven fuel distribution, causing local overheating or carbon deposition.
Spray hole consistency: Multi-spray hole injectors (such as 4-hole and 6-hole injectors) need to ensure that each spray hole sprays evenly, without any hole being blocked or the spray volume being significantly less (you can spray on a white cardboard to observe whether the oil trace distribution is symmetrical).
Dynamic spray test (for high-pressure common rail system)
Combined with an oscilloscope to detect the response time of the injector solenoid valve, ensure that the injection start/end time is synchronized with the ECU command to avoid hysteresis or early injection (hysteresis will cause combustion delay and black smoke; early injection will cause knocking).

Sealing test: prevent dripping and excessive oil return
The injector must be absolutely sealed in the non-injection state, otherwise it will cause fuel dripping (oil pollution, dilution and lubrication) or excessive oil return (insufficient oil supply).
Test method:
Needle valve sealing (closed state)
On the test bench, raise the pressure to "50-100bar lower than the injection pressure" (such as the standard pressure of 200bar, raised to 150bar), and maintain the pressure for 10 seconds:
Under normal circumstances, the pressure gauge pointer should not drop (or drop ≤5bar), and no fuel should drip out of the spray hole;
If the pressure drops rapidly (exceeds 10bar within 10 seconds), or oil droplets slowly seep out of the spray hole (≥1 drop within 10 seconds), it means that the matching surface of the needle valve and the needle valve body is worn and the seal fails.
Return oil volume test
Some injectors (such as electronically controlled injectors) are equipped with a return oil channel for cooling and pressure relief. The normal return oil volume should be ≤10mL/min (different standards for different models);
Use a measuring cylinder to collect the return oil within 1 minute. If it exceeds the standard value (such as a certain model requires ≤8mL/min, and the actual measurement is 15mL/min), it may be due to aging of the internal seal or stagnation of the needle valve, resulting in high-pressure oil leaking from the gap to the return oil circuit.

 Responsiveness test (for electronic fuel injectors)
Electronic fuel injectors control the opening/closing of the needle valve through a solenoid valve. The response speed directly affects the injection timing accuracy. The test needs to be combined with electronic equipment:

Solenoid valve resistance measurement
Use a multimeter to measure the resistance of the injector solenoid valve coil. The standard value is usually 0.5-3Ω (low resistance type) or 12-15Ω (high resistance type). A deviation of more than ±10% indicates that the coil is aging or short-circuited and needs to be replaced.
Injection timing verification
On the engine test bench or special equipment, compare the injection signal sent by the ECU with the actual injection time (detected by a pressure sensor or photoelectric sensor). If the time difference between the two exceeds 0.5ms, it means that the solenoid valve responds late, which may be due to valve core jamming or circuit failure, and needs to be repaired.

Auxiliary judgment of fault phenomenon
If the test conditions are limited, the abnormal function of the injector can be preliminarily judged in combination with the engine running symptoms:

Poor spray: black smoke from the engine (poor atomization, incomplete combustion of fuel), idle jitter, power reduction;
Failure of sealing: difficulty in cold start (drip leads to oil accumulation in the cylinder), increased oil level (fuel dilution of engine oil), oil traces on the exhaust pipe;
Abnormal pressure: weak acceleration (pressure is too low), knocking at start (pressure is too high).
Summary
The injector function test needs to be based on professional equipment data (such as test bench pressure, spray image), combined with appearance inspection (such as nozzle blockage, needle valve jamming) and fault phenomenon for comprehensive judgment. For injectors with excessive wear, seal failure or delayed response, it is recommended to replace them in time (especially precision parts, which are difficult to repair and difficult to guarantee accuracy) to avoid affecting engine life and emission compliance.