Service Procedure; Precautions In Servicing; Air Flow Meter - Subaru XT 1988 Service Manual

2-7 FUEL INJECTION SYSTEM
SERVICE PROCEDURE
Precautions in Servicing
1) Never connect the battery in reverse polarity.
• The MPFI control unit will be destroyed instantly.
• The fuel injector and other part will be damaged in just
a few minutes more.
2) Do not disconnect the battery terminals while the engine
is running.
• A large counter electromotive force will be generated in
the alternator, and this voltage may damage the electronic
parts such as MPFI control unit, etc.
3) Before disconnecting the connectors of each sensor and
the MPFI control unit, be sure to turn off the ignition switch.
• Otherwise, the MPFI control unit may be damaged.
4) The connectors to each sensor in the engine compartment
and the harness connectors on the engine side and body side
are all designed to be waterproof. However, it is still necessary
to take care not to allow water to get into the connectors
when washing the vehicle, or when servicing the vehicle on a
rainy day.
5) Every MPFI-related part is a precision part. Do not drop
them.
6) Observe the following cautions when installing a radio in
MPFI equipped models.
a. The antenna must be kept as far apart as possible
from the control unit.
b. The antenna feeder must be placed as far apart
as possible from the MPF I control unit and MPF I harness.
c. Carefully adjust the antenna for correct matching.
d. When mounting a large power type radio, pay special
attention to items a. thru c. above.
• Incorrect installation of the radio may affect the operation
of the MPF I control unit.
7) Before disconnecting the fuel hose, disconnect the fuel
pump connector and crank the engine for more than five
seconds to release pressure in the fuel system. If engine starts
during this operation, run it until it stops.
18
Air Flow Meter
INSPECTION
1) Check for leaks or damage in the connection between the
air intake boot and air flow meter. Repair any defect noted.
2) Remove the connectors from the air flow meter, the air
intake boot, and the air flow meter for the air cleaner case in
the order stated.
3) Check the exterior of the air flow meter for damage.
4) Check for foreign matter. water. or oil in the air passages,
especially in the by-pass. If any abnormality is noticed. replace
the air flow sensor.
5) If no defect is found in the visual checks above. conduct
the following inspections.
(1) Turn the ignition switch OFF (engine off).
(2) Attach the air flow meter to the air cleaner.
(3) Disconnect the air flow meter connector, and remove
the rubber cover from the connector.
Conduct the following checks by attaching the tester
check pins to the connector terminals on the side from
which the rubber cover has been removed.
I
Air flow meter
I
I
Rubber cover
Air flow meter connector (Body side)
Fig. 24
LgR: Burn·off signal
R : Power supply
S : GND
SR : GND
W : Sensor signal
L2-901