INJECTION NOZZLE CONSTRUCTION/OPERATION [WL-3]
id0114b5153200
• The injection nozzle consists of a nozzle holder, shim, nozzle spring, nozzle body, ring (identification color), and retaining nut, etc.
• When the fuel pressure from the fuel injection pump increases equal to the injection start pressure of the injection nozzle, the pressure is received at the conical part of the needle valve, and fuel is injected as the needle valve is lifted off its seat.
• Colored identification rings have been adopted so that injection nozzles can be attached to the fuel injection pump correctly. Accordingly, dispersion in fuel pressure during idling is eliminated and engine vibration is reduced.
Adjustment of Fuel Injection Start Pressure
• The adjustment of the fuel injection start pressure has been made possible by adjusting (selecting) the thickness of the shim in the injection nozzle and changing the set load of the nozzle spring. The injection start pressure of the injection nozzle is adjusted to approximately 10.8 MPa {110 kgf/cm2, 1,566 psi}. The thickness of the shim can be selected according to the following table. Every time the thickness of the shim increases/decreases 0.10 mm {0.0039 in}, the injection start pressure changes approximately 0.98 MPa {10.0 kgf/cm2, 142 psi}.
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Thickness of shim
mm {in}
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Thickness of shim
mm {in}
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0.10 {0.0039}
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0.52 {0.0205}
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0.20 {0.0078}
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0.54 {0.0213}
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0.30 {0.0118}
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0.56 {0.0220}
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0.40 {0.0157}
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0.58 {0.0228}
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0.50 {0.0197}
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0.80 {0.0315}
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Injection Nozzle Identification
• There are three kinds of injection nozzles; they are identified according to the identification colors of the ring installed on the retaining nut.
• Due to the adoption the electronic control type fuel injection pump, the idle vibration has been reduced by performing the cylinder and differential learning, however, the irregularity of the injection amount injected from the injection nozzle, which is the main cause of the idle vibration, should be minimized in advance. For this reason, the identification has been set to reduce the injection amount irregularity caused by the valve opening pressure of the injection nozzle. When disassembling/replacing the injection nozzle, it is necessary to perform the cylinder and differential learning after adjusting the four nozzles to the same injection pressure or replacing the four nozzles with new nozzles of the same colors.
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Ring identification color
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Initial adjustment pressure
MPa {kgf/cm2, psi}
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White
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11.4—11.6 {116—119, 1,650—1,692}
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Pink
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11.7—11.9 {119—122, 1,693—1,735}
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Yellow
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12.0—12.1 {122—124, 1.736—1,763}
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