Yanmar 6CXM-GTE2 Service Manual download pdf (Page 77)

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2) Half injection volume position

Discharge ends earlier as the rack is moved towards

zero from the maximum setting.

The fuel injection volume is decreased accordingly.

3) No fuel injection

With the rack set near zero, the intake/discharge port

in the barrel is always open, so no fuel is pressurized

(even though the plunger continues to reciprocate).

(4) Delivery valve

The delivery valve at the top of the plunger prevents fuel

in the fuel injection pipe from flowing back to the

plunger chamber and sucks up fuel from the nozzle valve

to prevent after-drip.

When plunger lead lines up with the discharge port of the

plunger barrel, the injection pressure drops, and the deliv-

ery valve is brought down by the delivery valve spring.

At the same time, the suck-back collar (1) blocks off the

fuel injection pipe and the delivery chamber, and the

valve continues descending until the seat (2) comes in

contact with the barrel.

The fuel oil pressure in the fuel injection pipe decreases

proportionately with the lowering of the valve (due to

increased volume).

This accelerates the nozzle to the nozzle valve, and sucks

up fuel from the nozzle to prevent dripping.

The result is a longer nozzle life and improved combus-

tion efficiency.

(5) Injection wave damping valve

The injection wave damping valve is fitted inside the

delivery valve holder. This valve prevents the cylindrical

pressure from being raised again by the injection reaction

and thus prevents secondary injection and cavitation.

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Yanmar 6CXM-GTE2 Service Manual Page 77