.
24
ELECTRONIC
FUEL
INJECTION
-
AFC
Description
Intake-Air
Sensor
The intake-air sensor
is
located
in
the engine compartment at the right-hand side between the air
filter
and the
throttle
housing (L) .
Construction
Aluminum
housing (A)
with
Bye-pass channel (5)
and
Adjustment
screw (6)
Air
sensor flap (1)
with
Back pressure valve (8)
and Damping vane (2)
Damping chamber (7)
Return spring (9)
Potentiometer (B)
with
Pump contacts
(C)
Temp
era
ture sensor I (D)
Operation
The volume
of
air that the
motor
can
draw in
is
determined
by
the position
of
the thro
ttle
valve.
The resultant air
flow
causes
the sensor flap
to
deflect against the return spring. T
he
flap deflection
is
transmitted via a shaft
to
the potentiometer which supplies a specific voltage
to
the con
trol
unit. The
temperature sensor I
is
connected
to
the potentiometer and influences the control signal volta
ge.
The injector which
is
activated by the control
unit
injects
an
exact amount
of
fuel appropriate
to
the
volume
of
intake-air.
The damping vane
is
designed
to
minimize sensor flap hunting. The
function
is
as
follows:
with
deflection
of
the flap the damping vane
is
forced
into
the damping chamber. The resultant compressed
air
within
the chamber
can
escape
only
through the
release
slit
(S)
. Sudden movements
and
hunting
is
thereby reduced.
A fraction
of
the air intake
is
detoured around the sensor flap via the bye-pass channel. The fuel-air
mixture
for
idle
can
be
set
by
means
of
the adjusting screw (6).
A pump contact
is
located
within
the potentiometer.
When
the sensor flap
is
deflected open the pump
contact
is
closed and the fuel pump started.
Probl
em
condition:
Motor
does
not
start;starting
dif
ficulties;
low
efficiency.
Troubleshooting:
Remove the plug connected
to
the potentiometer on the intake-air sensor. Connect
an
ohm meter
between the contacts 6 and
9.
value: 200
to
400
Mea
sure between contacts 7
an
d 8.
Nominal value: 120
to
200 7
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