Mitsubishi Montero (1991+). Manual — part 304

Air in fuel system Bleed air from system

Incorrect or contaminated Replace fuel

fuel

Injector nozzle malfunction Check nozzles, see

FUEL SYSTEMS

Engines Starts Injection pump timing Reset pump timing, see

and Idles Rough incorrect FUEL SYSTEMS

W/out Smoke or Engine not fully broken in Put more miles on

Noise, But Clears engine

After Warm-Up Air in system Bleed air from system

Injector nozzle malfunction Check nozzles, see

FUEL SYSTEMS

Engine Idles Blocked fuel filter Replace fuel filter

Correctly, Injection pump timing Reset pump timing, see

Misfires Above incorrect FUEL SYSTEMS

Idle Incorrect or contaminated Replace fuel

fuel

Engine Won’t Fast idle adjustment Reset fast idle, see

Return To Idle incorrect TUNE-UP

Internal injection pump Replace injection pump,

malfunction see FUEL SYSTEMS

External linkage binding Check linkage and

remove binding

Fuel Leaks On Loose or broken fuel line Check lines and

Ground connections

Internal injection pump Replace injection pump,

seal leak see FUEL SYSTEMS

Cylinder Injector nozzles sticking Test injectors, see

Knocking Noise open FUEL SYSTEMS

Very low nozzle opening Test injectors and/or

pressure replace

Loss of Engine Restricted air intake Remove restriction

Power EGR valve malfunction Replace EGR valve

Blocked or damaged exhaust Remove restriction

system and/or replace

components

Blocked fuel tank filter Replace filter

Restricted fuel filter Remove restriction

and/or replace filter

Block vent in gas cap Remove restriction

and/or replace cap

Tank-to-injection pump fuel Check fuel lines and

supply blocked connections

Blocked fuel return system Remove restriction

Incorrect or contaminated Replace fuel

fuel

Blocked injector nozzles Check nozzle for

blockage, see FUEL

SYSTEMS

Low compression Check valves, rings,

pistons, see ENGINES

Loud Engine Basic timing incorrect Reset timing, see

Noise With Black FUEL SYSTEMS

Smoke EGR valve malfunction Replace EGR valve

Internal injection pump Replace injection pump,

malfunction see FUEL SYSTEMS

Incorrect injector pump Check pressure, see

housing pressure FUEL SYSTEMS

Engine Cooling system leaks Check cooling system

Overheating and repair leaks

Belt slipping or damaged Check tension and/or

replace belt

Thermostat stuck closed Remove and replace

thermostat, see

ENGINE COOLING

Head gasket leaking Replace head gasket

Oil Light on at Low oil pump pressure Check oil pump

Idle operation, see ENGINES

Oil cooler or line Remove restriction

restricted and/or replace cooler

Engine Won’t Injector pump fuel solenoid Remove and check

Shut Off does not return fuel valve solenoid and replace

to OFF position if needed

VACUUM PUMP DIAGNOSIS

Excessive Noise Loose pump-to-drive Tighten screws

assembly screws

Loose tube on pump assembly Tighten tube

Valves not functioning Replace valves

properly

Oil Leakage Loose end plug Tighten end plug

Bad seal crimp Remove and re-crimp

seal

FUEL INJECTION TROUBLE SHOOTING

NOTE: This is GENERAL information. This article is not intended

to be specific to any unique situation or individual vehicle

configuration. The purpose of this Trouble Shooting

information is to provide a list of common causes to

problem symptoms. For model-specific Trouble Shooting,

refer to SUBJECT, DIAGNOSTIC, or TESTING articles available

in the section(s) you are accessing.

BASIC FUEL INJECTION TROUBLE SHOOTING CHART

CONDITION POSSIBLE CAUSE CORRECTION

Engine Won’t Cold start valve inoperative Test valve and

Start (Cranks circuit

Normally)

Poor connection;vacuum or Check vacuum and

wiring electrical

connections

Contaminated fuel Test fuel for water

or alcohol

Defective fuel pump relay Test relay and

or circuit wiring

Battery too low Charge and test

battery

Low fuel pressure Test pressure regul-

ator and fuel pump,

check for restricted

lines and filters

No distributor reference Repair ignition

pulses system as necessary

Open coolant temperature Test sensor and

sensor circuit wiring

Shorted W.O.T. switch in Disconnect W.O.T.

T.P.S. switch, engine

should start

Defective ECM Replace ECM

Fuel tank residual pressure Test for fuel

valve leaks pressure drop after

shut down

Hard Starting Disconnected hot air tube Reconnect tube and

to air cleaner test control valve

Defective Idle Air Control Test valve operation

(IAC) valve and circuit

Shorted, open or misadjusted Test and adjust or

T.P.S. replace T.P.S.

EGR valve open Test EGR valve and

control circuit

Poor Oxygen sensor signal Test for shorted or

circuit

Incorrect mixture from PCV Test PCV for flow,

system check sealing of oil

filter cap

Poor High Speed Low fuel pump volume Faulty pump or

Operation restricted fuel

lines or filters

Poor MAP sensor signal Test MAP sensor,

vacuum hose and

wiring

Poor Oxygen sensor signal Test for shorted or

open sensor or

circuit

Open coolant temperature Test sensor and

sensor circuit wiring

Faulty ignition operation Check wires for

cracks or poor con-

nections, test

secondary voltage

with oscilloscope

Contaminated fuel Test fuel for water

or alcohol

Intermittent ECM ground Test ECM ground

connection for

resistance

Restricted air cleaner Replace air cleaner

Restricted exhaust system Test for exhaust

manifold back

pressure

Poor MAF sensor signal Check leakage

between sensor and

manifold

Poor VSS signal If tester for ALCL

hook-up is available

check that VSS

reading matches

speedometer

Ping or Knock on Poor Knock sensor signal Test for shorted or

Acceleration open sensor or

circuit

Poor Baro sensor signal Test for shorted or

open sensor or

circuit

Improper ignition timing See VEHICLE EMISSION

CONTROL LABEL (where

applicable)

Check for engine Low coolant, loose

overheating problems belts or electric

cooling fan

inoperative

NOTE: For additional electronic fuel injection trouble shooting

information, see the appropriate article in the ENGINE

PERFORMANCE section (not all vehicles have Computer Engine

Control articles). Information is provided there for

diagnosing fuel system problems on vehicles with electronic

fuel injection.

IGNITION SYSTEM TROUBLE SHOOTING

NOTE: This is GENERAL information. This article is not intended

to be specific to any unique situation or individual vehicle

configuration. The purpose of this Trouble Shooting

information is to provide a list of common causes to

problem symptoms. For model-specific Trouble Shooting,

refer to SUBJECT, DIAGNOSTIC, or TESTING articles available

in the section(s) you are accessing.

Ignition Secondary Trouble Shooting Chart

START: Visually inspect Spark Plug Wires, Coil Wires,

Plug Wire Boots, Rotor, and Distributor Cap for

signs of damage.