This will be a very long blog to explain how to repair the common rail injector. The following is a simple directory that we will update gradually. Finally, it was made into a PDF file for our customers.

Let’s get started here:

How Bosch injectors work and some related failure forms

The role of the injector in the common rail system is to spray accurate fuel into the combustion chamber at the right time to ensure that the fuel is fully burned.

Each common rail injector oil channel includes a low-voltage part and a high-pressure part:

The injector body (1) holds together the multi hole nozzle (2) with the solenoid coil assembly (3) and contains the valve body (4). Thearmature of the solenoid (5) moves together with a ball. The ball is opening and closing the so called A-throttle. The valve body has two orifices (A- and Z-throttles) controlling pressure in the control chamber (6) and a corresponding control piston (7). The control piston is in direct physical connection with the nozzle needle (8).

The injector consists of five main components:

The injector body (1) holds together the multi hole nozzle (2) with the solenoid coil assembly (3) and contains the valve body (4). Thearmature of the solenoid (5) moves together with a ball. The ball is opening and closing the so called A-throttle. The valve body has two orifices (A- and Z-throttles) controlling pressure in the control chamber (6) and a corresponding control piston (7). The control piston is in direct physical connection with the nozzle needle (8).

When the injector does not work, the nozzle needle valve blocks the hole, preventing high-pressure fuel injection into the combustion chamber. When the injector solenoid coil receives the ECU signal, armature is sucked up due to the electromagnetic power generated by the coil, at the same time the valve ball and valve ball holder are elevated by the oil pressure, so does the nozzle needle valve. At this moment the hole opens, the fuel in good atomization form and sprays it into the cylinder. The amount of fuel sprayed is also precisely controlled by the ECU, and each complete injection process can be subdivided into the following five stages:

(1) off (no injection)

(2) open (Start injection)

(3) Full opening (continuous injection)

(4) Off (injection volume reduction)

(5) completely closed (stop injection)

Through the analysis of the failure of the main parts of the following common rail injectors, we can know the basic reason of the failure of the injectors, and then work out the preventive ways.
(1) Solenoid valve
Electromagnetic coil melting failure: the power voltage is too large or work time is too long, caused the electromagnetic coil melting.
Preventive way: Do not apply external voltage to the injectors artificially.
The form of failure is shown in the following figure:
jyhy diesel bosch injector solenoid

（2）The loose of injector high-pressure connector:

Injector high-pressure connector loose cased fuel leakage.
Failure reason: when remove the high-pressure tube, making the connector rotated then loose.
Preventive way: When disassembling the high pressure oil pipe, fix the high pressure joint with a wrench
Bosch solenoid

（3）Corrosion inside high pressure common rail injector

Preventive measures: ensure the quality of fuel oil, and drain water periodically during the rough filtration period

The form of failure is shown in the following figure:

Corrosion inside high pressure common rail injector

（4）High-pressure common rail injector: internal parts are worn (eg valve components, etc.)

Symptoms: The vehicle’s fault light is on, black smoke is emitted when the gas is accelerating, and the power is insufficient.

Reason for failure: Fuel contains a large amount of impurities

Preventive measures: ensure the quality of the filter, especially the quality of the fine filter (the use of non-standard filters is strictly prohibited). Install an air filter on the fuel tank vent to avoid fuel pollution caused by sand and dust in the external environment and ensure fuel quality.

The form of failure is shown in the following figure:

High-pressure common rail injector: internal parts are worn (eg valve components, etc.)

（5）Sealing steel gasket: air blown in cylinder

Symptom: Combustion gas penetrates into the return oil and causes insufficient engine power.

Failure reason: Impurities cause pits on the surface of the copper gasket to reduce sealing.

Precautions: Copper gaskets cannot be reused. To ensure the cleanliness of the copper gasket, the bottom of the engine mounting hole and the nozzle cap of the injector when installing the injector, only use a copper gasket to avoid the remaining gasket in the engine mounting hole.

The form of failure is shown in the following figure:

Sealing steel gasket air blown in cylinder

（6）Common rail injector: external damage

Symptom: The fuel injector does not work properly, which causes the engine to work unstable.

Cause of failure: Improper installation and incorrect operation.

Precautions: Tighten the solenoid valve caps, terminals and wiring harness plugs when installing the injector

Common rail injector external damage