New High Quality Diesel Injector 250-1313 10R-9617 373-4087 376-0509 379-0509 386-1752 20R-1264 For CAT C3500B

1. Preparation
Tools and equipment
Mechanical pressure-regulated injector: fuel pressure gauge (0-20MPa), manual fuel pump, connecting oil pipe, wrench.
Electronic common rail injector: diagnostic instrument (such as X-431, KT600), high-pressure fuel pressure gauge (0-200MPa), oscilloscope, multimeter.
Others: clean rag, diesel (for cleaning), maintenance manual (to obtain standard pressure value).
Safety measures
Turn off the engine and disconnect the negative pole of the battery (to avoid malfunction of electronic components).
The common rail system needs to be depressurized first: loosen the bleed screw near the fuel filter or rail pressure sensor, and confirm that there is no oil pressure before operating.

2. Steps for pressure detection of mechanical pressure-regulated injector
1. Connect the pressure gauge
Find the injector inlet pipe, disconnect it and connect the fuel pressure gauge (connected in series in the pipeline through a three-way connector).
Make sure the connection is firm to avoid oil leakage (you can use diesel to lubricate the interface first).
2. Manual pressure test (without engine)
Use a manual fuel pump to slowly increase pressure and observe the pressure gauge value:
Opening pressure test: When the injector starts to spray fuel, the peak value of the pressure gauge is the injection opening pressure (reference manual for standard values, such as 10-15MPa).
Sealing test: Keep the pressure 1MPa lower than the opening pressure (if the standard opening pressure is 12MPa, pressurize to 11MPa), and observe whether the pressure drops by more than 0.5MPa within 30 seconds (if it exceeds, it means that the seal is poor).
3. Detection when the engine is running
Start the engine, run at idle speed, and record the stable value of the pressure gauge (it should be the idle pressure set by the manufacturer, such as 6-8MPa).
Accelerate quickly to full throttle and observe the pressure fluctuation:
Normal: The pressure should rise quickly to the highest value (such as 12-15MPa), and the fluctuation range is ≤10%.
Abnormal: The pressure rises slowly or fluctuates too much, which may be due to the weakness of the pressure regulating spring or the spool stuck.

3. Steps for testing the pressure of electronic common rail injectors
1. Reading the rail pressure sensor (indirect detection)
Connect the vehicle OBD interface through the diagnostic instrument, enter the "Data Stream" menu, and read the real-time data of the common rail pressure sensor:
Idle condition: The standard rail pressure is usually 60-100MPa (such as 80MPa for a certain model).
Full load condition: The rail pressure should rise to 150-200MPa (depending on the model).
Abnormal judgment:
Rail pressure is lower than the target value: it may be a high-pressure pump failure, injector leakage, or pressure limiting valve opening.
Rail pressure is higher than the target value: it may be a pressure control solenoid valve (PCV) stuck or ECU command abnormality.
2. Directly connect to the high-pressure pressure gauge
Find the pressure test interface on the common rail pipe (usually with a dust cap), and connect the high-pressure fuel pressure gauge:
Start the engine and compare the diagnostic instrument data with the pressure gauge value (the error should be ≤5%).
During sudden acceleration, observe whether the pressure gauge rises synchronously with the speed (delay or lag may be due to slow response of the solenoid valve).
3. Solenoid valve response test
Use an oscilloscope to measure the drive signal of the pressure control solenoid valve (PCV):
When idling, the signal should be a low-frequency pulse (such as a frequency of 10-20Hz and a duty cycle of about 20%-30%).
When accelerating, the pulse frequency and duty cycle should increase (such as the frequency rises to 50Hz and the duty cycle is 60%-80%).
Use a multimeter to measure the resistance of the solenoid valve coil:
The standard value is usually 1-3Ω (slightly different for different models, if it is ∞ or 0Ω, the coil is damaged).
4. Unit injector test (disassembly required)
Remove the injector and install it on the common rail injector test bench:
Input the ECU analog signal to test the injection volume and pressure under different working conditions (such as idle, 2000rpm, full load).
Compare the measured value with the manufacturer's standard (e.g. the full-load injection volume of a certain injector should be 100±5ml/300 times).

4. Common abnormal causes and treatment
Detection phenomenon Possible cause Treatment method
Pressure is lower than the standard value. The pressure regulating spring is weak, the valve core is stuck, and the sealing surface is worn. Replace the spring, clean or grind the valve core, and replace the injector.
Pressure is too high and cannot be adjusted. The spring preload is too large, and the solenoid valve cannot be opened to relieve pressure. Adjust the spring preload, repair or replace the solenoid valve.
Pressure fluctuates violently. The fuel filter is blocked, the oil circuit is inlet, and the solenoid valve is intermittently stuck. Replace the filter element, exhaust air, and clean the solenoid valve.
Solenoid valve has no signal. ECU failure, line break or short circuit, sensor failure. Repair ECU, check the line, and replace the sensor.
5. Precautions
High-pressure risk of common rail system: It is forbidden to face the injector outlet during operation to avoid high-pressure fuel penetrating the skin and causing damage.
Cleaning requirements: Before disassembling the injector, the outside must be thoroughly cleaned to prevent dust from entering the oil circuit (the interface can be cleaned with a chemical cleaner).
Data recording: Compare the pressure data under different working conditions, and conduct comprehensive analysis based on parameters such as engine speed and load.