Yanmar 4LHA-HTP Operation Manual page 426

Chapter 3 Fuel Injection Equipment
1. Fuel Supply System
1-4 Injection volume c o n t r o l
(1) Full injection volume p o s i t i o n
When the rack is set a t maximum setting, maximum
volume of fuel is discharged.
when the top of t h e
intake port in the b a r r e l .
groove which is p o s i t i o n e d at the widest stroke
part, lines up with t h e discharge port, prolonging
the injection time a n d increasing the volume of
fuel injected.
This setting is n o r m a l l y used for starting and max.
output operation.
Effective stroke
(2) Half injection volume position
Discharge ends earlier as the rack is moved to-
wards zero from the maximum setting.
The fuel injection volume is decreased accordingly.
Effective stroke
(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).
Injection occurs
plunger lines up with the
A t this time, the lead
3-2-4
The delivery valve at the top of the plunger pre-
vents 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 the plunger lead lines up with the discharge
port of the plunger barrel, the injection pressure
drops, and the delivery valve is brought down by
the delivery valve spring.
«1.
S i
I T I
*
Suck-back
stroke
A t the same time, the suck-back collar (1) blocks
off the fuel injection pipe and the delivery cham-
ber, 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 closing of the nozzle valve, and
sucks up fuel from the nozzle to prevent dripping.
The result is a longer nozzle life and improved
combustion efficiency.
4LHA Series
V
4
A2)
1=1