Cessna T188C - Page 260

MODEL
188
&
T188
SERIES
SERVICE
MANUAL
k. Disconnect
control
from
strainer.
On aircraft
18800833
thru 18801374,
the fuel
pump
1. Remove
screws securing
strainer,
switch is a
split-rocker type;
the right half
positions
m.
Disconnect
all fuel lines
and electrical
connec-
are "HI,
" "LO" and
off and
the left half
positions
are
tione
from
fuel
pump.
"MAX
HI"
and
off.
The
right
half
of the
switch
in-
n-
Loosen
clamp
securing
pump.
corporates
an intermediate
"LO"
position
used
for
o. Remove
shut-off
valve,
fuel strainer
and
pump
normal
starting,
and a
"HI" position
(when
the
top
from
aircraft
as a
unit.
of the
switch
is fully
depressed)
for
vapor
purging
p. Reverse
the preceding
steps
for
installation.
during
hot
engine
starts.
Maximum
fuel
flow
is pro-
duced
when
the
left
half
of
the
switch
is
held
in
the
12-51.
ELECTRIC
FUEL
PUMP
CIRCUIT.
(MODEL,
spring-loaded
"MAX
HI"
position.
In the
"MAX
HI"
A188-SERIES).
(Refer
to
figure
12-1).
position,
an interlock
within
the switch
automatically
trips
the
right
half
of
the
switch
to
its
"HI"
position.
12-52.
DESCRIPTION.
The
electric
auxiliary
fuel
When
the
spring-loaded
left
half
of
the switch
is re-
pump, which
supplies
fuel
flow
for starting
and
for
leased,
the
right half
will
remain
in the "HI"
position
engine
operation
if the
engine-driven
fuel
pump
should
until
manually
returned
to
the off
position.
With the
fail, is
controlled
by the
auxiliary
fuel
pump
switch,
right
half
of the
switch
in the
"LO"
position,
and
the
mounted
on
the instrument
panel.
The switch
is a
starter
button
depressed,
the
auxiliary
fuel
pump
three-position
toggle
switch.
The
down
position,
will
operate
at a
low
flow rate
(providing
proper
fuel
labeled
START,
is used
for starting
the
engine.
With
mixture
for
starting)
as the
engine
is being
turned
the
switch
in this
position
and the
starter
button
push-
over with
the
starter.
ed
in,
the
auxiliary
fuel
pump
will
operate
at
a flow
rate
that
provides
the
proper
fuel
mixture
for
start-
NOTE
ing
as
the
engine
is
being
turned
over
with
the
starter.
The
auxiliary
fuel
pump
will
not
operate
in
NOTE
the
"LO"
position
until the
starter
button
is
depressed.
The
auxiliary
fuel
pump
will
not
operate
with
With
the
right
hall
of
the
switch
in the
"HI"
position,
the
switch
in
the
START
position
until
the
the
pump
operates
at
one
of
the
two
flow
rates
that
starter
button
is
pushed
in.
are
dependent
upon
the
setting
of
the
throttle.
With
the
throttle
open
to
a cruise
setting,
the
pump
is
op-
The
up
position
of
the
switch,
labeled
EMERGENCY,
erating
at
a
high
capacity
to
supply
sufficient
fuel
is
used
for
engine
operation
if the
engine-driven
fuel
flow
to
maintain
flight.
When
the
throttle
is
moved
pump
should
fail,
or
for
vapor
purging
in
extremely
toward
the
closed
position
(as
during
letdown,
land-
hot
weather.
When
the
switch
is
in this
position,
the
ing
and
taxiing),
the
fuel
pump
fow
rate
is
automati-
auxiliary
fuel
pump
can
operate
at
two
flow
rates
de-
caly
reduced,
preventing
an
excessively
rich
mix-
pending
on
the
setting
of
the
throttle.
With
the
ture
during
these
periods
of
reduced
engine
speed.
throttle
at
a
cruise
setting,
the
auxiliary
pump
is
When
the
engine-driven
fuel
pump
is functioning
and
operating
at
maximum
capacity,
supplying
sufficient
the
auxiliary
fuel
pump
is
turned
on
"HI",
a
fuel/air
fuel
flow
to
maintain
flight
with
the
engine-driven
ratio
considerably
richer
than
best
power
is
pro-
pump
inoperative.
When
throttle
is
moved
toward
duced
unless
the
mixture
is
leaned.
If the
auxiliary
the
closed
position,
as
during
let-down,
landing,
and
fuel
pump
switch
is
accidentally
placed
on
"HI"
(with
taxiing,
a mechanically-actuated
switch
electrically
master
switch
on)
with
the
engine
stopped
and
the
reduces
the
auxiliary
fuel
pump
flow
rate
by
means
mixture
rich,
the
intake
manifolds
will
be
flooded.
of
a resistor
in
the
pump
power
circuit.
This
action
automatically
prevents
an
excessively
rich
mixture
On
Aircraft
18801375
thru
18801824,
the
switching
during
these
periods
of
reduced
engine
speed.
circuits
to
the
electric
fuel
pump
are
simplified.
The
The
auxiliary
fuel
pump
is
not
to
be on
EMERGENCY
new
switch
appears
identical
to the
red-yellow
inter-
during
normal
operation
because,
with
the
engine-
locking
switch
previously
used.
The
right-hand
yel-
driven
pump
functioning,
a
fuel-air
ratio
consider-
low
rocker
switch
does
not
have
the
center
ON"
posi-
ably
richer
than
best
power
is
produced.
If
fuel
tion
which
was
interconnected
to
the
starter
circuit,
vapor
is
affecting
engine
operation,
the
vapor
may
but
it
still
has
the
low
and
high
boost,
depending
on
be
purged
by
turning
the
auxiliary
fuel
pump
switch
throttle
position
The
throttle-actuated
switch
func-
to
EMERGENCY
and
leaning
the
mixture
as
required
tions off the throttle quadrant as described in the
to
prevent
an
excessively
rich
mixture.
Successful
to prevent an excessiy
rich mixture.
Successful
preceding
paragraph.
Closing
the throttle adds
more
vapor
purging
is evidenced
by smooth
engine
oper-
resistance
to the
low
boost
circuit.
The
left-hand
ation
and
steady
and
normal
fuel
flow
indications
red rocker
switch
functions
as
before
("OFF"
- "O-
with
the auxary
fuel
pump
switch OFF
red rocker
switch
functions
as before
("OFF"
- "MO-
MENTARY
ON")
for
high
boost
operation.
The
mo-
NOTE
mentary
high boost
function
controlled
by the
red
rocker
switch,
bypasses
the
throttle
switch
circuit
If
the auxiliary
fuel pump
switch
is acciden-
and provides
full
fuel pump
capacity,
regardless
of
tally turned to EMERGENCY
(with master
throttle
position.
switch
on)
with
the
engine
stopped,
intake
manifolds
will
be
flooded
unless
the
mixture
is
in idle
cut-off.
12-25