New High Quality Diesel Nozzle L137PRD for Injection Nozzle Diesel Engine Parts

Preliminary inspection: appearance and symptom analysis
1. Observe the engine running status
Idle speed jitter: single or multiple nozzles are blocked/poor atomization, resulting in uneven cylinder operation.
Weak acceleration or bursting: wrong injection timing or insufficient injection amount, too lean or too rich mixture.
Abnormal exhaust:
Diesel engine emits black smoke: poor nozzle atomization, nozzle wear and expansion (uncontrolled injection amount).
Gasoline engine emits black smoke/white smoke: nozzle dripping causes too rich mixture, or water is mixed in the fuel.
2. Check the external symptoms of the fuel system
Leakage traces: aging or improper installation of the nozzle seal ring leads to fuel leakage (especially near the cylinder head).
Abnormal noise: The electronically controlled fuel injector (such as solenoid valve type) should have a regular "click" sound when working. If there is no sound or abnormal sound, it may be a circuit fault or valve core stuck.
3. Read the fault code
Operation: Use a diagnostic instrument (such as OBD-II device) to read the fault code stored in the ECU.
Common code examples:
P0201~P0204 (fault in each cylinder injector circuit): may be caused by wiring harness disconnection or solenoid valve damage.
P0172 (too rich mixture)/P0171 (too lean): indirectly reflects nozzle blockage or dripping.

Professional detection: tool and equipment diagnosis
1. Fuel pressure test
Purpose: to determine whether the nozzle injection pressure is normal (need to be combined with the standard value in the vehicle model manual).
Steps:
Connect the fuel pressure gauge to the fuel rail (gasoline engine) or the high-pressure fuel pump oil pipe (diesel engine).
Start the engine and observe the pressure changes during idling/acceleration:
Normal situation:
Gasoline engine MPI system: idle pressure is about 0.25~0.35MPa, and it rises slightly during rapid acceleration.
Diesel engine common rail system: idle pressure is 50~100MPa, and can reach 150~200MPa at full load.
Abnormal judgment:
Pressure is too low: nozzle leakage or fuel pump failure;
Pressure is too high: nozzle is blocked or pressure regulating valve fails.
2. Injector atomization test (disassembly test)
Applicable scenario: When the nozzle atomization is suspected to be poor, the nozzle needs to be removed for bench testing.
Tools: Injector tester (or ultrasonic cleaning machine supporting equipment).
Test content:
Sealing test: Apply standard pressure (such as 18MPa for diesel engines) and observe whether there is dripping within 10 seconds (≤1 drop/10 seconds allowed).
Atomization morphology observation:
Normal: The oil mist is fine and dense cone, without obvious oil droplets or deflection;
Abnormal: Oil beam bifurcation, inclusions or "straight" injection (spray hole is blocked or worn).
Uniformity of injection quantity: Under the same pressure, measure the difference in injection quantity of each cylinder nozzle in the same time (usually ≤5% is normal).
3. Waveform analysis (electronic fuel injector)
Tool: Oscilloscope connected to the injector control harness.
Test method: Start the engine and observe the injection signal waveform:
Normal waveform:
Voltage-driven type (such as gasoline engine): pulse width changes with speed/load (about 1~2ms at idle speed, 4~6ms at full load), and there should be an inductive recoil spike (about 30~100V) when closing.
Current-driven type (such as diesel common rail): The waveform shows the "peak-hold" mode (first open the valve core with high current, then maintain it with low current).
Abnormal judgment:
No waveform: wiring harness disconnection, ECU drive module damage;
Spike missing: injector solenoid valve coil short circuit (internal turn short circuit);
Abnormal pulse width: ECU signal error or sensor (such as air flow meter) failure.
4. Cylinder pressure test
Indirect judgment: Poor nozzle atomization or dripping will cause incomplete cylinder combustion and cylinder pressure drop.
Operation: Use a cylinder pressure gauge to measure the pressure of each cylinder (all spark plugs/injectors need to be removed, the throttle is fully open, and the engine is started 3~5 times).
Standard value: The pressure of each cylinder should be close to the value specified by the manufacturer (usually gasoline engines ≥80% of the original factory value, and the difference between each cylinder is ≤10%).
Abnormal prompt: The cylinder pressure of a certain cylinder is obviously low, which may be a nozzle failure or a cylinder sealing problem (it is necessary to combine other tests to eliminate mechanical failures such as piston rings and valves).

Comparative elimination method: replacement and data analysis
1. Inter-cylinder interchange test
Operation: Interchange the suspected faulty nozzle with the nozzle of other cylinders (the position needs to be marked) to observe whether the fault is transferred.
Judgment logic:
If the fault is transferred to other cylinders with the nozzle, it is confirmed that the original nozzle is damaged;
If the fault remains unchanged, it may be a circuit, sensor or ECU problem.
2. Data flow analysis (combined with diagnostic instrument)
Read parameters:
Short-term fuel correction value (STFT):
If STFT continues to be >+10%, the fuel nozzle may be blocked, causing the mixture to be too lean;
If STFT continues to be <-10%, the fuel nozzle may be leaking, causing the mixture to be too rich.
Injection pulse width: If the pulse width is greater than the normal value at idle (such as more than 3ms), the fuel nozzle may be blocked or the intake system may be leaking.
Oxygen sensor signal: Abnormal fluctuation frequency (such as 0.1~0.9V for gasoline engines, 8 jumps per second), reflecting an imbalance in the mixture.
3. Cylinder disconnection test (applicable to multi-cylinder engines)
Operation: Disconnect the wiring harness plugs of each cylinder injector in turn at idle speed (or disconnect the high-pressure oil pipe for diesel engines) and observe the changes in engine speed.
Judgment criteria:
Normal cylinder: The speed drops significantly after the cylinder is cut off (such as a gasoline engine drops 50~100rpm, and the diesel engine sound changes suddenly);
Faulty cylinder: The speed does not change or changes slightly after the cylinder is cut off, indicating that the cylinder nozzle is not working properly (blocked, circuit disconnected or valve core stuck).

Special scenario: Differences between diesel engines and gasoline engines
1. Key points for diesel engine injector diagnosis
High-pressure common rail system:
A special diagnostic instrument is required to read the rail pressure sensor data and compare the target pressure with the actual pressure deviation (usually ≤±5MPa);
Check the return oil volume of the injector: The return oil pipe flow at idle speed should be ≤200ml/minute (too much may be caused by needle valve wear).
Traditional plunger pump system:
By adjusting the fuel supply advance angle, observing the engine abnormal sound and exhaust changes, determine whether the timing is correct;
Check the injector spring preload (using a torque wrench or spring tester) to confirm that the injection pressure meets the standard.
2. Gasoline Direct Injection System (GDI)
Visual inspection: Use an endoscope to observe the distribution of carbon deposits in the combustion chamber. If the carbon deposits on the intake valve or piston top of a cylinder increase abnormally, the nozzle atomization may be poor, causing the fuel to flush the cylinder wall.
Leak test: After stopping, observe the pressure drop rate of the fuel rail (normally, the pressure drop within 30 minutes is ≤0.1MPa). If it drops rapidly, the nozzle or fuel pump seal may fail.

Precautions
Safe operation:
The pressure of the diesel engine high-pressure system is extremely high. The fuel pressure must be released before disassembly (such as waiting for 5 minutes after turning off the key) to avoid high-pressure oil spraying and injuring people.
The gasoline engine needs to disconnect the negative pole of the battery to prevent accidental start during maintenance.
Tool adaptation:
Different models have different injector interfaces (such as Bosch, Denso, Delphi systems), and corresponding adapters and testers must be used.
Avoid misjudgment:
Fuel nozzle failure may be related to the fuel pump, fuel filter, intake sensor (such as MAP, MAF), etc., and it is necessary to gradually eliminate external factors before determining the fuel nozzle problem.