workshop
Manual
Rolls Royce Silver Shadow
&
Bentley
T
Ser~es
Chapter
K
SYMPTOM
--mirQre
--
(Symptom
11
and
12
arc
applicable
to
cars
from
SRH.8742
onwards).
11.
High
float
chamber
depression
also
spitting
back
in the
car-
buretters.
12.
Low
float
+her
depression
also
small
~ncrease
m fuel
consumption.
POSSIBLE CAUSE
11.
(a)
Weakening
device filter blocked
or blockage in rubber hose or
bleed orifice.
(b)
Dislodged venturi in weakening
device.
Items
(c), (d), (e) and
(f)
are applicable
only when a Fuel evaporation
emission control system is fitted.
(c) Evaporation losscontrol canister
Nter blocked.
(d) Incorrect connection of weak-
ener hose to valance adaptor or
evaporation loss control canister.
(e) Incorrect purge flow rate (greater
than
1
cu. ft./minute).
(f)
Evaporationloss control canister
obstructed.
12. (a) Blockage in engine side of weak-
ening device.
(b)
Float chamber and weakening
device air leaks.
(c) Float chamber connection air
leaks
as
far
as
and including the
one way valves in the fuel drain
and vent pipes.
(d) Engine intake air temperature
below
18°C.
(64°F.).
(e) Inoperative weakener cut-off
valve.
(f)
Leaks in weakening device, car-
buretter tapping or weakener
cut-off valve.
(g)
Faulty cut-off valve.
(h)
A dirty or faulty float chamber
drain valve.
Items
(i) and
(j)
are applicable o@y
when
a
Fuel
evaporation
emls-
sion control system is fitted.
(i)
A
dirty or faulty float chamber
vent valve.
(j)
Incorrect purge flow rate (cor-
rect
flow rate
1
cu. ft./minute).
ACTION
11.
(a) Renew filter or remove the block-
age.
(b)
Renew the weakening device.
(c) Renew filter or remove blockage.
(d) Ensure connections are fitted
correctly; rectify if necessary.
(e) Renew purge line restrictor.
(f) Remove obstruction or fit new
canister.
12. (a) Remove blockage.
(b)
Renew gaskets and washers.
Ensure that both float chamber
lids are tight also that all con-
nections are tight.
(c) Check that all pipe connections
are tight and seating correctly
and rubber hoses are in a good
condition. Check that the one
way valve assemblies are clean
and correctly seated also that
it is tightly assembled
(d) Allow engine to warm up.
(e) Renew valve.
(f) Check and tighten any loose
connections also check the con-
dition of sealing washers and
renew if necessary.
(g) Disconnect the two pipes fitted
to the cut-off valve then connect
the pipes by fitting a small piece
of thick walled rubber tube over
the two end nipples; a piece of
tube similar to the type fitted to
the refrigeration fast-idle solen-
oid would suffice. Run the
engine and check the float
chamber depression, if the
depression is correct, the cut-off
valve is faulty and should be
renewed.
(h)
Remove foreign matter or renew
valve.
(i)
Remove foreign matter or renew
valve.
(j)
Remove any blockage in the
purge line restrictor or renew
the restrictor. Also remove any
blockage in the purge line filter
or the pipes situated between the
gulp valve to carburetter 'Tee'
piece pipe and evaporation loss
control canister.
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