Weifang 495 - Page 83

T"he fuel from t11e feed pump flows, after being· filtered, into
the upper housing of the injection pUlnp through the:inlet banjo
. .
connection bolt an~ fills up the space above the pluqget. When the
fuel pressure reaches 49kpa, the checkvalve opensa~athe exces-
sive fuel flows hackto the :deIivery pump via returppipe.
As the plunger moves upward to cover the rPo~ hpleson the
barrel thouroghly, the ·ftiel is compressed. The plun¥er;~()e~:on to
mOve up until the increased fuel pressure canovei.cPni~,th~force of
the delivery. valve spring,tne deliveryvalve l~~s:iio~;:it~s;arand
the fl:lel flows into.the.injec:~or through the fuel injeCtion' pipe.
The plunger moves ... upward continuously, 'the' helical groove
on it is connected with the spill- port on the bareel, the 'residual
compressed fuel above the plunger top flows back to the low pres-
sure chamber within the p~urrlp hOllsing along the vertical passage
and helical groove on .the ,plunger a.nd thro:ugh the apill- port on
the barrel. ThJ;1s ,-fuel ·press\l:re within thespace.above the plunger
drops ,the deliv:eryvalve returns to its seat-under· the action of ~-its
spring and the 'ftiel delivery ceases.
During the end of the fuel injectiorl' the relief'piston of the de-
livery valve makes the fuel pres.sure within tpe injection pipe dn;>p
rapidly to make the nozzle terminate the fuel injection insta.nta-
neously and t.her~by avoid "dribbling~'after injection of th~ fuel.
Theq~antit}1'of fuel delivered by the pump varies with the en-
gine load and its variation is~.arried ,o·ut by turning the plunger of
the pump which is achieved by the movement o.f the· control rod"
cqntrol fork and the adjucting.arm. The axial ffi.ovem.ent of the ~on
trol rod is governed by the governor.
The injection pump is provided with a ~entrifugal \laria.ble
speed type governor (Fig. 21) mounted on pump's rear end. The
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