The Working Mode and Some Failure Modes of Bosch Injector

by MOU YONG HONG on December 01, 2021

This article mainly introduces the working mode of the fuel injector, the composition of the fuel injector, the reasons why the fuel injector cannot work, and the four major aspects of preventing fuel injector failure.

The Working Mode and Some Failure Modes of Bosch Injector

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Let’s start here:

The working mode and some failure modes of Bosch injector

The role of the injector within the common rail system is to spray accurate fuel into the combustion chamber at the proper time to make sure that the fuel is fully burned.

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

The injector consists of 5 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) The armature of the solenoid (5) moves alongside a ball. The ball is opening and shutting the so-called A-throttle. The valve body has two orifices (A- and Z-throttles) controlling pressure within the control chamber (6) and a corresponding control piston (7) The control piston is in direct physical reference to the nozzle needle (8) When the injector doesn't work, the nozzle needle valve blocks the opening, preventing a high-pressure fuel injection system into the combustion chamber. When the injector solenoid coil receives the ECU signal, the armature is sucked up thanks to the electromagnetic power generated by the coil, at an equivalent time the valve ball and valve ball holder are elevated by the pressure, so does the nozzle needle valve. At this moment the opening opens, the fuel in good atomization form, and sprays it into the cylinder. the quantity of fuel sprayed is additionally precisely controlled by the ECU, and every complete injection process are often subdivided into the subsequent 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 most parts of the subsequent common rail injectors, we will know the essential reason for the failure of the injectors, then compute the preventive ways.

(1) Solenoid valve

Electromagnetic coil melting failure: the facility voltage is just too large or time period is just too long, caused the electromagnetic coil melting.
Preventive way: don't apply external voltage to the injectors artificially.
The form of failure is shown within the following figure:

(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 oil pipe, fix the high joint with a wrench

(3)Corrosion inside high common rail injector

Preventive measures: make sure the quality of heating oil, and drain the water periodically during the rough filtration period

The form of failure is shown within the following figure:

(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 therefore the power is insufficient.

Reason for failure: Fuel contains an outsized amount of impurities

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

The form of failure is shown within the following figure:

(5)Sealing steel gasket: air blown in the 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 scale back sealing.

Precautions: Copper gaskets can't be reused. To make sure the cleanliness of the copper gasket, rock bottom of the engine mounting hole, and therefore the nozzle cap of the injector when installing the injector, only use a copper gasket to avoid the remaining gasket within the engine mounting hole.

The form of failure is shown within the following figure:

(6)Common rail injector: external damage

Symptom: The fuel injector doesn't work properly, which causes the engine to figure unstable.

Cause of failure: Improper installation and incorrect operation.

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

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