Common Rail Injector (CRI) Construction & Working

CRI Injectors

The construction of injector is simple. Like other type of injectors, it is having a plunger and nozzle. There is a high-pressure line from the common rail which feeds diesel to the injectors continuously. This is available at the tip of nozzles at all the times. Opening and closing of nozzle is done by the valve movement. At top end of the valve, there IA ball which is moved with the help of solenoid (magnet). As the signal os ON, the ball gets lifted and causes the lift of plunger due to pressure difference. This movement opens the nozzle hole and fuel gets injected. As soon as the signal is OFF, ball goes to original position and injection stops. N and OFF of the signal to the solenoid is controlled by ECU ad it takes fraction of seconds for the action. More than one injections are possible during the stroke. Time between ON and OFF of the signal can decide the quantity of Injection. In other words, quantity and timing of fuel is controlled in nozzle.

The leak off line is at the top of the injector and is attached to the return line.

Do’s and Don’ts for Injectors:

• Assure maximum of cleanliness in the work area, cylinder head and around injector to Avoid contamination of injector openings with dust, particles, etc
• Remove protective caps only shortly before assembly process.
• Handle injector with extremely care: If a new injector falls down, it must be scrapped, even if visually seems ok.
• Pay attention to ensure that there are no contacts between hard materials on nozzle & or magnet group while fitting in cylinder head.
• Tighten clamping brackets with given torque.
• Apply correct torque on injector high pressure pipe screw nut.
• Assemble back leak pipe connectors on injectors. Check if connector O-Ring is in OK condition. Press back leak pipe connector vertically down by hand until piece snaps in place.
• In case of damage of fuel return line assembly, the entire assembly has to be replaced.
• Electrical plug connection must audibly snap in during installation.

 

• Do not connect injector directly to any external power source (battery) for checking purpose. This will lead to total damage of electrical parts of injector.
• Do not plug / unplug electrical connection if ignition is on
• Do not damage or cover DMC (data matrix code).
• Do not install back leak pipe without circlip.
• Do not extremely bend or squeeze cables, avoid contact with sharp edges.

 

What is Data Matrix Code?

The CRDI injectors are provided with the Data Matrix Code (DMC). This is an alphanumeric 12-digit code printed on the top of Injector. The code no. is required to be inserted into the Laptop screen while assembling the injector to the particular cylinder. At the time of removal and assembly of the injector, it is to be ensured that the same injector should go to the particular cylinder.

The code is useful to fine-tune the timing between signal and actuation. (the time is 10 microseconds per command).