1995 SUBARU LEGACY Fuel injection system

1. Engine Trouble in General
Numbers shown in the chart refer to the possibility of reason for the
trouble in order (“Very often”to“Rarely”)
1—Very often
2—Sometimes
3—Rarely
TROUBLE
Engine will not start.
Rough idle and engine stall
Low output, hesitation and poor acceleration
Surging
Engine does not return to idle.
Dieseling (Run-on)
After burning in exhaust system
Knocking
Excessive engine oil consumption
Excessive fuel consumption Starter does not turn.
Initial combustion does not occur.
Initial combustion occurs.
Engine stalls after initial combustion.
POSSIBLE CAUSE
STARTER
2Defective battery-to-starter harness
3Defective starter switch
3Defective inhibitor switch
23Defective starter
BATTERY
1Poor terminal connection
1Run-down battery
2Defective charging system
1111111111 1Fuel injection system Diagnostics II System.>
75
2-3DIAGNOSTICS
1. Engine Trouble in General

1. Engine Cooling System
Trouble Possible cause Corrective action
Over-heatinga. Insufficient engine coolantReplenish engine coolant, inspect for leakage, and
repair.
b. Loose timing belt Repair or replace timing belt tensioner.
c. Oil on drive belt Replace.
d. Malfunction of thermostat Replace.
e. Malfunction of engine coolant pump Replace.
f. Clogged engine coolant passage Clean.
g. Improper ignition timingInspect and repair ignition control system.

h. Clogged or leaking radiator Clean or repair, or replace.
i. Improper engine oil in engine coolant Replace engine coolant.
j. Air/fuel mixture ratio too leanInspect and repair fuel injection system.

k. Excessive back pressure in exhaust system Clean or replace.
l. Insufficient clearance between piston and cylinder Adjust or replace.
m. Slipping clutch Repair or replace.
n. Dragging brake Adjust.
o. Improper transmission oil Replace.
p. Defective thermostat Replace.
q. Malfunction of electric fanInspect radiator fan relay, engine coolant temperature
sensor or radiator motor and replace there.
Over-coolinga. Atmospheric temperature extremely low Partly cover radiator front area.
b. Defective thermostat Replace.
Engine coolant
leaks.a. Loosened or damaged connecting units on hoses Repair or replace.
b. Leakage from engine coolant pump Replace.
c. Leakage from engine coolant pipe Repair or replace.
d. Leakage around cylinder head gasket Retighten cylinder head bolts or replace gasket.
e. Damaged or cracked cylinder head and crankcase Repair or replace.
f. Damaged or cracked thermostat case Repair or replace.
g. Leakage from radiator Repair or replace.
Noisea. Defective drive belt Replace.
b. Defective radiator fan Replace.
c. Defective engine coolant pump bearing Replace engine coolant pump.
d. Defective engine coolant pump mechanical seal Replace engine coolant pump.
19
2-5DIAGNOSTICS
1. Engine Cooling System

1. General
1. GENERAL DESCRIPTION

The on-board diagnostics (OBD) system detects and
indicates a fault in various inputs and outputs of the com-
plex electronic control. CHECK ENGINE malfunction indi-
cator lamp (MIL) in the combination meter indicates occur-
rence of a fault or trouble.

Further, against such a failure or sensors as may disable
the drive, the fail-safe function is provided to ensure the
minimal driveability.

The OBD system incorporated with the vehicles within
this engine family complies with Section 1968.1, California
Code of Regulations (OBD-II regulation). The OBD system
monitors the components and the system malfunction
listed in Engine Section which affects on emissions.

When the system decides that a malfunction occurs, MIL
illuminates. At the same time of the MIL illumination or
blinking, a diagnostic trouble code (DTC) and a freeze
frame engine conditions are stored into on-board com-
puter.

The OBD system stores freeze frame engine condition
data (engine load, engine coolant temperature, fuel trim,
engine speed and vehicle speed, etc.) into on-board com-
puter when it detects a malfunction first.

If the OBD system detects the various malfunctions
including the fault of fuel trim or misfire, the OBD system
first stores freeze frame engine conditions about the fuel
trim or misfire.

When the malfunction does not occur again for three
trips, MIL is turned off, but DTC remains at on-board com-
puter.

The OBD-II system is capable of communication with a
general scan tool (OBD-II general scan tool) formed by ISO
9141 CARB.

The OBD-II diagnostics procedure is different from the
usual diagnostics procedure. When troubleshooting OBD-II
vehicles, connect Subaru select monitor or the OBD-II gen-
eral scan tool to the vehicle.
A: ENGINE
1. ENGINE AND EMISSION CONTROL SYSTEM

The Multipoint Fuel Injection (MFI) system is a system
that supplies the optimum air-fuel mixture to the engine for
all the various operating conditions through the use of the
latest electronic technology.
With this system fuel, which is pressurized at a constant
pressure, is injected into the intake air passage of the cyl-
inder head. The injection quantity of fuel is controlled by an
intermittent injection system where the electro-magnetic
injection valve (fuel injector) opens only for a short period
of time, depending on the quantity of air required for one
cycle of operation. In actual operation, the injection quan-
2
2-7ON-BOARD DIAGNOSTICS II SYSTEM
1. General

10. General Diagnostics Table
1. FOR ENGINE
12345678910111213
Problem parts
Mass air flow sensor
Engine coolant temperature sensor (*1)
Throttle position sensor
Crankshaft position sensor & Camshaft position sensor (*2)
Idle air control solenoid valve
Knock sensor
Purge control solenoid valve
EGR valve
Fuel injection parts (*3)
Ignition parts (*4)
Fuel pump and relay
A/C switch and A/C cut relay
Engine torque control signal circuitSymptom
1 Engine stalls during idling.   
2 Rough idling    
3 Engine does not return to idle.
4 Poor acceleration   
5Engine stalls or engine sags or hesi-
tates at acceleration.    
6 Surge   
7 Spark knock
8 After burning in exhaust system  
*1: The mark,, indicates the symptom occurring only in cold temperatures.
*2: For items with the mark,, ensure the secure installation of crankshaft position sensor and camshaft position sensor. Replacement is
not necessary.
*3: Check fuel injector, fuel pressure regulator and fuel filter.
*4: Check igniter, ignition coil and spark plug.
NOTE:
Malfunction of parts other than the above is also possible. Refer to 1. Engine Trouble in General [K100] in Repair Section 2-3 of the Ser-
vice Manual.
128
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. General Diagnostics Table

OBD0172
F: DTC P0115
—ENGINE COOLANT TEMPERATURE
SENSOR CIRCUIT MALFUNCTION (TW)—
OBD0173A
DESCRIPTION:
The engine coolant temperature sensor is located on the
engine coolant pipe which is made of aluminum alloy. Its
thermistor changes resistance with respect to temperature.
A engine coolant temperature signal converted into resis-
tance is transmitted to the ECM to control the amount of
fuel injection, ignition timing, purge control solenoid valve,
etc.
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Hard to start

Erroneous idling

Poor driving performance
156
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code

OBD0265A
DESCRIPTION:

The MFI system employs a gallery type (side-feed type)
fuel injector.

The gallery type fuel injector is installed in the fuel pipe
to allow cooling of the injector by the fuel.

The features of this type of fuel injector are as follows:
1) High heat resistance
2) Low driving noise
3) Easy to service
4) Small size

The fuel injector injects fuel according to the valve open
signal received from the ECM.

The nozzle is attached on the top of the fuel injector. The
needle valve is lifted by the solenoid coil through the
plunger on arrival of the valve open signal.

Since the injection opening, the lifted level of valve and
the regulator-controlled fuel pressure are kept constant,
the amount of fuel to be injected can be controlled only by
the valve open signal from the ECM.
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Failure of engine to start

Engine stalls.

Erroneous idling

Rough driving
204
2-7ON-BOARD DIAGNOSTICS II SYSTEM
11. Diagnostics Chart with Trouble Code