Valmet 309 - Page 93

FEED PTIf
F€ed
pump
4l I
l. Hand
pump
2. Plug
f. Seallng
rlng
4. Spr I ng
5.
Va lve
6. Valve fappei
7.
Body
8. 0-rlng
9,
Plsion
10. Sprlng
ll.
Seallng rlng
12. Plug
lf. Oaskol-
14. l{asher
15. Nut
The fuel feed
pressure
ls
produced
by a
plston
pumo
llxed
fo ihe
slde
of the
Iniectlon
pump.
The
puDp
ls drlven by
ihe eccen+rlc
loca+ed on
ihe lnjecilon
pump
carnshaf+.
The anouni
of
fuel
+hai cofiEs fron l-he
{e€d
purp
exceeds
conslderably
+he
fuel needed by
+he Iniectlon
pump.
The
extra fuel ls led
ihrQgh
th€ over-
flor
valve
back +o
ihe fuel tank.
Thls erfra
fuel
cools
-th€
lnjec+lon
purp
and ble€ds
the
fuel svs+em.
9lo
The
eccenirlc on ihe lnjecilon
purp
camshafi
(l)
presses
dorn the feed
pump
pls+on
(5).
Thls
ollors
fuel
lo enfer from feed
pump
lnlei
chaitber
(7)
In+o
prossure
chamber
(4)
vla
pressure
valve
(8)
and ihe
plsfon
sprlng
stretchas
(
Infermedlaie
stroke).
After
fhe eccen+rlc has rota+ed
oast
lts loD
deod
c6n+re lf ls
followed
upvard
by fhe
plsfon,
pressure pln
(f)
and ihe rol ler tappet
(2)
prassed
by ihe
sprlng. Durlng thls
phase
fuel
ls
fed through
fllier to
the InJecilon
punp
ond ai
ihe
same tlmo fuel ls suckgd
through
lnlei valve
(6)
to +he feed
pump
lnlel
chamber
(pressure
stroke).
Durlng
the
pressure
stroke
ihe leed
pump pumps
ngarly
all +hs necessary fuel anount lnfo +he
lnJec+lon
pump.
Durlng lhe ln+ormedlöta
stroke
It dellvers
only a small amount whlch corres-
ponds
to
the
prossure pln pushlng
ltself lnio
+he
pressur€
chamber.
WhEn the
prgssure
ln ihe feed
plpg
excegds €
cerialn value fhe
sprlng forces the
plston
up
rlih
only
pari
of the stroke and +he fuel
raie
Is correspondlngly
lorer, l.e. +he
hlgher
ihe
back
pressurg
ln tha feed
plpo,
fhe
smaller
ihe
4nouni of fuel dellvered
by
+ho
pump.
9
lt
A.
Pressure
sfroke
B.
Intermedlaie
stroke
l.
lnJsctlon
pump
camshaft
2. Rol ler
iappet
5. Pressure pln
4.
pressure
chamber
S.
plston
6.
Inlet valvg
7.
Inle+
chamber
8.
pressure
va lv9
9-7