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)
Potent
iometer
(B)
with
Pump contacts (C)
T
emp
era
ture
sensor
I
(D)
Operation
The volume
of air that
th
e
motor can draw in is
determined
by the position
of
the
th
ro
ttle
valve
.
The resultant
air
flow
causes the sensor
flap to
deflect against
the return
spring
.
T
he
fla
p deflection is
transmitted via a shaft
to the potentiometer which
supplies
a
specific
voltage to the
c
on
trol
un
i
t
.
The
temperature
sensor
I is
connected
to the potentiometer
and
influences the control
signal v
ol
ta
ge.
The injector which is
activated
by the
control
unit injects an
exact amount
of fuel appropria
te
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
.
Prob
l
em
condition:
Motor does not start
;
starting dif
f
iculties; low
efficiency.
Troubleshooting
:
Remove the
plug
connected to the potentiometer on the intake-air sensor
. C
onnect an
ohm
m
eter
between
the contacts 6 and 9.
value: 200 to 400
Mea
s
ure between contact
s
7 an
d
8
.
Nom
inal
value
:
120 to 200
7
\
4
