Chapter 3 Fuel Injection Equipment
1. Fuel Supply System
4LHA Series
1-4
Injection
volume
control
(1) Full injection volume position
When
the rack is set at maximum setting, maximum
volume of fuel is discharged.
Injection
occurs
when the top of the plunger lines up
with
the
intake
port
in the barrel. At this time, the lead
groove which is positioned at the widest stroke
part, lines up
with
the discharge
port,
prolonging
the injection time and increasing the volume of
fuel injected.
This
setting is normally 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
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.
Si
IT
I
V
*
4
1=1
Suck-back
stroke
A2)
At 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.
(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).
3-2-4
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