1991 MITSUBISHI MONTERO fuse
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Excessive cylinder wear Rebore or replace
block
Excessive valve guide Worn or loose bearing
clearance
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Gap Bridged Deposits in combustion Clean combustion
chamber becoming fused chamber of deposits
to electrode
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Blistered Engine overheating Check cooling system
Electrode
Wrong type of fuel Replace with correct
fuel
Loose spark plugs Retighten spark plugs
Over-advanced ignition Reset ignition timing
timing see ENGINE PERFORMANCE
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Pre-Ignition or Incorrect type of fuel Replace with correct
Melted Electrodes fuel
Incorrect ignition timing Reset ignition timing
see ENGINE PERFORMANCE
Burned valves Replace valves
Engine Overheating Check cooling system
Wrong type of spark plug, Replace with correct
too hot spark plug, see
ENGINE PERFORMANCE
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Chipped Severe detonation Check for over-
Insulators advanced timing or
combustion
Improper gapping Re-gap spark plugs
procedure
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Rust Colored Additives in unleaded Try different fuel
Deposits fuel brand
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Water In Combus- Blown head gasket or Repair or replace
tion Chamber cracked head head or head gasket
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NOTE: Before diagnosing an electronic ignition system, ensure that
all wiring is connected properly between distributor, wiring
connector and spark plugs. Ignition problem will show up
either as: Engine Will Not Start or Engine Runs Rough.
BASIC ELECTRONIC IGNITION TROUBLE SHOOTING CHARTS
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CONDITION POSSIBLE CAUSE CORRECTION \
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Engine Won't Open circuit between Repair circuit
Start distributor and bulkhead
connector
Open circuit between Repair circuit
bulkhead connector and
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full load. The Kent-Moore J-39021 is such a tool, though there are
others. The Kent-Moore costs around $240 at the time of this writing
and works on many different manufacturer's systems.
The second method is to use a lab scope. Remember, a lab
scope allows you to see the regular operation of a circuit in real
time. If an injector is having an short or intermittent short, the lab
scope will show it.
Checking Available Voltage At the Injector
Verifying a fuel injector has the proper voltage to operate
correctly is good diagnostic technique. Finding an open circuit on the
feed circuit like a broken wire or connector is an accurate check with
a DVOM. Unfortunately, finding an intermittent or excessive resistance
problem with a DVOM is unreliable.
Let's explore this drawback. Remember that a voltage drop due
to excessive resistance will only occur when a circuit is operating?
Since the injector circuit is only operating for a few milliseconds at
a time, a DVOM will only see a potential fault for a few milliseconds.
The remaining 90+% of the time the unloaded injector circuit will show
normal battery voltage.
Since DVOMs update their display roughly two to five times a
second, all measurements in between are averaged. Because a potential
voltage drop is visible for such a small amount of time, it gets
"averaged out", causing you to miss it.
Only a DVOM that has a "min-max" function that checks EVERY
MILLISECOND will catch this fault consistently (if used in that mode).\
The Fluke 87 among others has this capability.
A "min-max" DVOM with a lower frequency of checking (100
millisecond) can miss the fault because it will probably check when
the injector is not on. This is especially true with current
controlled driver circuits. The Fluke 88, among others fall into this
category.
Outside of using a Fluke 87 (or equivalent) in the 1 mS "min-\
max" mode, the only way to catch a voltage drop fault is with a lab
scope. You will be able to see a voltage drop as it happens.
One final note. It is important to be aware that an injector
circuit with a solenoid resistor will always show a voltage drop when
the circuit is energized. This is somewhat obvious and normal; it is a
designed-in voltage drop. What can be unexpected is what we already
covered--a voltage drop disappears when the circuit is unloaded. The
unloaded injector circuit will show normal battery voltage at the
injector. Remember this and do not get confused.
Checking Injector On-Time With Built-In Function
Several DVOMs have a feature that allows them to measure
injector on-time (mS pulse width). While they are accurate and fast to\
hookup, they have three limitations you should be aware of:
* They only work on voltage controlled injector drivers (e.g
"Saturated Switch"), NOT on current controlled injector
drivers (e.g. "Peak & Hold").
* A few unusual conditions can cause inaccurate readings.
* Varying engine speeds can result in inaccurate readings.
Regarding the first limitation, DVOMs need a well-defined
injector pulse in order to determine when the injector turns ON and
OFF. Voltage controlled drivers provide this because of their simple
switch-like operation. They completely close the circuit for the
entire duration of the pulse. This is easy for the DVOM to interpret.
The other type of driver, the current controlled type, start
off well by completely closing the circuit (until the injector pintle
opens), but then they throttle back the voltage/current for the
duration of the pulse. The DVOM understands the beginning of the pulse
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Fig. 8: Diode (Light Emitting)
Fig. 9: Defogger Grid
Fig. 10: Fuse
Fig. 11: Fusible Link
Fig. 12: Ground
Fig. 13: Glow Plug Resistor (In-Line) or Mirror Heater
Fig. 14: Injector (Diesel) or Photocell (Gasoline)
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Fig. 15: Internal Fuse, Thermal Limiter
Fig. 16: Lamp (Dual Element)
Fig. 17: Lamp (Single Element)
Fig. 18: Motor
Fig. 19: Resistor (Internal)
Fig. 20: Sensor, Thermistor
Fig. 21: Solenoid
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WIR IN G D IA G RAM S
1991 M it s u bis h i M onte ro
1991 Wiring Diagrams
Mitsubishi
Montero
IDENTIFICATION
COMPONENT LOCATION MENU
COMPONENT LOCATIONS TABLE \
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Component Figure No. (Location)
A/C RELAYS .......................... 4 (C 12), 4 (A-B 15)
A/C SYSTEM ................................. 4 (A-C 12-15)
ALTERNATOR ................................... 1 (B-C 1-2)
ALTERNATOR RELAY ............................... 1 (C 1-2)
AUTO FREE-WHEELING HUB CONTROL UNIT ............. 3 (D 11)
BACK DOOR LOCK SW ............................... 7 (B 27)
BACK-UP LT SW (M/T) ............................. 7 (A 26)
BATTERY .......................................... 1 (A 1)
BLOWER SWITCH ................................. 4 (A-B 12)
BUZZER .......................................... 5 (E 17)
CARGO LIGHT ..................................... 6 (A 23)
CIG LIGHTER ..................................... 3 (E 11)
CLOCK ........................................... 3 (E 11)
COLUMN SW ..................................... 5 (A-E 19)
CRUISE CONTROL SYSTEM ...................... 4 (D-E 13-15)
DEFOGGER ...................................... 7 (C-D 27)
DIAG CONNECTION .................................. 2 (E 7)
DIMMER CONTROL SWITCH ............................ 3 (E 8)
DIR FLASHER ..................................... 5 (C 16)
DIR SWITCH ...................................... 5 (C 19)
DOME LT ............................... 6 (A 23), 7 (A 24)
DOOR LOCK SYSTEM ........................... 6 (D-E 21-23)
DOOR SWITCHES ......................... 5 (D 17), 6 (C 23)
FRONT WIPER SYSTEM ........................... 5 (A 16-17)
FUEL GAUGE UNIT ................................. 6 (C 22)
FUEL PUMP ........................................ 2 (C 4)
FUSE BLOCK .................................... 3 (C 9-10)
HAZARD FLASHER .................................. 5 (C 16)
HAZARD SW ....................................... 5 (B 16)
HEAD LIGHT WASHER RELAY ....................... 5 (C-D 17)
HEATER RELAY .................................... 4 (A 12)
HORN SWITCH ..................................... 5 (E 19)
IGNITION COIL .................................... 2 (E 4)
IGNITION SW ..................................... 3 (A 11)
ILLUMINATION LIGHTS ............................ 3 (D-E 8)
INHIBITOR SW ..................................... 3 (A 9)
INSTRUMENT CLUSTER ............................ 6 (A-D 20)
KEY REMINDER SW ................................. 5 (E-17)
LIGHT CONTROL RELAY ............................. 5 (E 19)
LIGHT SWITCH .................................... 5 (D 19)
MAIN FUSE LINKS ................................ 1 (A 1-2)
METER UNIT ...................................... 6 (E 20)
MPI CONTROL RELAY ................................ 2 (B 4)
MPI CONTROL UNIT ............................... 2 (A 4-7)
NOISE FILTER ..................................... 2 (E 6)
OVERDRIVE CONTROL RELAY .......................... 3 (A 8)
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OVERDRIVE SWITCH ................................. 3 (A 8)
PARKING BRAKE SWITCH ............................ 6 (A 21)
POWER TRANSISTOR ................................. 2 (D 4)
POWER WINDOWS .............................. 7 (B-E 24-26)
RADIO (PARTIAL) ............................... 3 (D-E 10)
REAR BLOWER SWITCH .............................. 4 (D 12)
REAR WIPER .................................... 5 (D-E 16)
SEAT BELT WARNING TIMER ......................... 5 (D 18)
STARTER .......................................... 1 (C 3)
STOP LIGHT SWITCH ..................... 4 (E 13), 5 (C 16)
SUB FUSE LINKS ................................... 1 (A 3)
SUNROOF ...................................... 7 (A 24-25)
WIPER SWITCH .................................. 5 (A-B 19)
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WIRING DIAGRAMS
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Fig. 3: Fuse Block, Ignition Sw, Inhibitor Sw, (A/T) (Grid 8-11)