MG MGB - Faulty Diaphragm Action; Noisy Pump; Pump Operates Without Delivering Fuel

THE
FUEL
SYSTEM
D
to
a
restriction in
the
pipeline
between
the
pump
and the
tank. This
may
be cleared
by
the
use
of
compressed
air
after
removing
the fuel
tank ■ller
cap.
It should
be
noted,
however, that
compressed
air
should
not
be
passed through the
pump
as
this
will
cause
serious
damage
to
the valves.
(iv)
FAULTY
DIAPHRAGM
ACTION
In the
event
of the
previous
operations
failing
to
locate the
trouble,
it
may
be
due
to
a
stiffening
of
the diaphragm
fabric
or
the
presence
of
abnormal
friction
in
the
rocker ‘throw-over’
mechanism,
or
a
combination
of
both.
To
remedy
these
faults
the
coil
housing
should
be
removed
and the
diaphragm
■exed
a
few
times,
taking
care
not to
lose
any
of
the
11
rollers
under the
diaphragm.
Prior
to
this
resetting
it is
advisable
to
apply,
very
sparingly,
a
little thin
oil
to
the throw-over
spring
spindles
at
the
point where they
pivot
in
the brass
rockers.
The diaphragm/armature
assembly
should then
be
reassembled
in
accordance
with
the
instructions
given
under that
heading.
2.
NOISY
PUMP
If the
pump
is
noisy in
operation,
an
air
leak
at
the
suction
line
may
be the
cause.
Such
a
leak
may
be checked
by
disconnecting
the fuel
pipe
from
the
carburetter
and
allowing
the
pump
to
discharge
into
a
suitable
container
with
the
end of
the
pipe submerged.
The
emission of
@QtD
@
96:9
A50951W
Fig. D.9
The
HS4
carburetter
1. Jet adjusting
nut.
5. Float-chamber
securing
nut.
2. Throttle
stop
screw.
6. Jet
link.
3. Choke
or
fast-idle
screw.
7.
Jet
head.
4
8.
.
Jet
locking
nut.
Vacuum
ignition
take-off.
MGB.
Issue5. 69615
2
3
4
A6279
Fig.
D.1O
A
sectional
View of the
HS4
carburetter
5. Piston lifting
pin.
6. Needle
securing
screw.
7. Oil damper
reservoir.
Jet locking
nut.
Jet
adjusting
nut.
Jet head.
Feed
tube from ■oat-
chamber.
9W3”?
continuous
bubbles
at
this
point will con■rm
the
existence
of
an
air
leak.
The fault
should
be
recti■ed
by
carrying
out
the following
procedure:
(3)
Check
that
all
connections
from
the fuel
tank
to
the
pump
are
in good
order.
(b)
Check
that
the
inlet
union
is
tight
and
that the
sealng
‘0’
ring is
not
damaged.
(c)
Check
that
the
coil housing
securing
screws
are
well
and
evenly
tightened.
Air leaks
on
the
suction side
cause
rapid
operation
of
the
pump
and
are
the
most
frequent
cause
of
permanent
failure.
3.
PUMP
OPERATES
WITHOUT
DELIVERING
FUEL
If the
pump
operates
continuously
without
delivery of
fuel
the
most
likely
causes
are:
(a)
A
very
serious
air
leak
on
the
suction
side
or,
(b)
Foreign
matter
lodged
under
one
of the
valves,
particularly
the inlet
valve.
To
remedy
(a)
see
Section
2
(above).
In
order
to
remove
any
foreign
matter
lodged
under
the
valves, these
should
be
removed
for
cleaning
and
great
care
taken
that
the
plastic
material
of
the
valve
disc
is
not
scratched
or
damaged
during this
operation.
'
D.9