Siemens-Common Rail System – Fuel injectors

fig 1 24 Siemens Common Rail System – Fuel injectors

A Fuel injector (1.4L Duratorq-TDCi (DV) diesel engine and 1.8L Duratorq-TDCi (Kent) diesel engine)
B Fuel injector (2.0L Duratorq-TDCi (DW) diesel engine)
C Fuel injector head
D Hydraulic servo system
E Fuel injector nozzle
1 Connector for PCM
2 Piezo actuator
3 High pressure fuel line connection
4 Copper sealing ring
5 Emission standard coding
6 Fuel return port
7 Retainer
8 Fuel return adapter
9 O-ring seal
10 Adapter fastening clip
11 Plastic bush

Depending on the engine version, fuel injectors of different designs are used. Their basic construction and function are however largely the same.

The start of injection and the injection quantity specified by the PCM are implemented by means of the piezo-electrically controlled fuel injectors.

Depending on engine speed and engine load, the fuel injectors are actuated by the PCM with an opening voltage of approximately 70 V. The piezo effect causes the voltage within the piezo element to rise to approximately 140 V.

The fuel injectors inject the appropriate fuel quantity for all engine operating conditions into the combustion chambers in accordance with the combustion cycle.

Extremely short switching times of approximately 200 μs permit extremely rapid reaction to changes in the operating conditions. The fuel quantity to be injected can thus be metered very precisely.

The fuel injectors are divided into three assemblies:
• fuel injector head, including the piezo actuator,
• hydraulic servo system,
• fuel injector nozzle.

NOTE: In the case of repairs, the fuel injectors cannot be dismantled, as this results in their destruction.

NOTE: The wiring harness connectors of the piezo fuel injectors must on no account be detached when the engine is running. The piezo actuators remain expanded for a certain period after the power is interrupted, i.e.
the fuel injectors remain open. Effect: Continuous injection and engine damage!

The copper sealing rings must be replaced during servicing.

Special features

1.4L Duratorq-TDCi (DV) diesel engine:
• In newer versions, a distinction is made between Emission Standard III and Emission Standard IV fuel injectors. A code is stamped onto the fuel injector shaft for this purpose:
– E3 = Emission Standard III,
– E4 = Emission Standard IV.

2.0L Duratorq-TDCi (DW) diesel engine:
• A guide bushing located in the lower part of the cylinder head and a plastic bushing on the fuel injector shaft serve to fasten the fuel injector.

03. September 2018 by sam
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