Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual — part 781
6A–4
ENGINE MECHANICAL (6VD1 3.2L)
Engine Diagnosis
Hard Starting
1. Starting Motor Does Not Turn Over
Troubleshooting Procedure
Turn on headlights and starter switch.
Condition
Possible cause
Correction
Headlights go out or dim
considerably
Battery run down or under charged
Recharge or replace battery
considerably
Terminals poorly connected
Clean battery posts and terminals
and connect properly
Starting motor coil circuit shorted
Overhaul or replace
Starting motor defective
Overhaul or replace
2. Ignition Trouble — Starting Motor Turns Over But Engine Does Not Start
Spark Test
Disconnect an ignition coil from any spark plug. Connect
the spark plug tester 5–8840–0383–0, start the engine,
and check if a spark is generated in the spark plug tester.
Before starting the engine, make sure that the spark plug
tester is properly grounded. To avoid electrical shock, do
not touch the part where insulation of the ignition coil is
broken while the engine is running.
Condition
Possible cause
Correction
Spark jumps across gap
Spark plug defective
Clean, adjust spark gap or replace
Ignition timing incorrect
Refer to Ignition System
Fuel not reaching fuel injector(s) or
engine
Refer to item 3 (Trouble in fuel
system)
Valve timing incorrect
Adjust
Engine lacks compression
Refer to item 4 (Engine lacks
compression)
No sparking takes place
Ignition coil disconnected or broken
Connect properly or replace
Electronic Ignition System with
module
Replace
Poor connections in engine harness
Correct
Engine Control Module cable
disconnected or defective
Correct or replace
3. Trouble In Fuel System
Condition
Possible cause
Correction
Starting motor turns over and spark
occurs but engine does not start
Fuel tank empty
Fill
occurs but engine does not start.
Water in fuel system
Clean
Fuel filter clogged
Replace filter
Fuel pipe clogged
Clean or replace
Fuel pump defective
Replace
Fuel pump circuit open
Correct or replace
Evaporative Emission Control
System circuit clogged
Correct or replace
Multiport Fuel Injection System faulty
Refer to “Electronic Fuel Injection”
section
6A–5
ENGINE MECHANICAL (6VD1 3.2L)
4. Engine Lacks Compression
Condition
Possible cause
Correction
Engine lacks compression
Spark plug loosely fitted or spark
plug gasket defective
Tighten to specified torque or replace
gasket
Valve timing incorrect
Adjust
Cylinder head gasket defective
Replace gasket
Valve incorrectly seated
Lap valve
Valve stem seized
Replace valve and valve guide
Valve spring weakened or broken
Replace
Cylinder or piston rings worn
Overhaul engine
Piston ring seized
Overhaul engine.
Engine Compression Test Procedure
1. Start and run the engine until the engine reaches
normal operating temperature.
2. Turn the engine off.
3. Remove all the spark plugs.
4. Remove ignition coil fuse (15A) and disable the
ignition system.
5. Remove the fuel pump relay from the relay and fuse
box.
6. Engage the starter and check that the cranking speed
is approximately 300 rpm.
7. Install cylinder compression gauge into spark plug
hole.
8. With the throttle valve opened fully, keep the starter
engaged until the compression gage needle reaches
the maximum level. Note the reading.
9. Repeat the test with each cylinder.
If the compression pressure obtained falls below the
limit, engine overhaul is necessary.
Limit; 1000 kPa (145 psi)
6A–6
ENGINE MECHANICAL (6VD1 3.2L)
Rough Engine Idling or Engine Stalling
Condition
Possible cause
Correction
Trouble in fuel injection system
Idle air control valve defective
Replace
Throttle shutting off incomplete
Correct or replace
Throttle position sensor circuit open
or shorted
Correct or replace
Fuel injector circuits open or shorted
Correct or replace
Fuel injectors damaged
Replace
Fuel pump relay defective
Replace
Mass Airflow Sensor circuit open or
poor connections
Correct or replace
Mass Airflow Sensor defective
Replace
Manifold Absolute Pressure Sensor
circuit open or poor connections
Correct or replace
Manifold Absolute Pressure Sensor
defective
Replace
Engine Coolant Temperature Sensor
circuit open or poor connections
Correct or replace
Engine Coolant Temperature Sensor
defective
Replace
Intake Air Temperature sensor circuit
open or poor connections
Correct or replace
Intake Air Temperature sensor
defective
Replace
Vehicle Speed Sensor circuit open or
shorted
Correct or replace
Vehicle Speed Sensor defective
Replace
Trouble in emission control system
Engine Control Module defective
Replace
Canister purge valve circuit open or
poor connections
Correct or replace
Canister purge valve defective
Replace
Evaporative Emission Canister
Purge control valve defective
Replace
Trouble in ignition system
Refer to “Hard Start”
Others
Engine lacks compression
Refer to “Hard Start”
Valve incorrectly seated
Lap valve
Air Cleaner Filter clogged
Replace filter element
Valve timing incorrect
Readjust
Idle air control valve broken
Replace
Fast idle solenoid defective
Replace
Positive Crankcase Ventilation valve
defective or clogged
Replace
6A–7
ENGINE MECHANICAL (6VD1 3.2L)
Rough Engine Running
Condition
Possible cause
Correction
Engine misfires periodically
Ignition coil layer shorted
Replace
Spark plugs fouling
Clean or install hotter type plug
Spark plug(s) insulator nose leaking
Replace
Fuel injector(s) defective
Replace
Engine control module faulty
Replace
Engine knocks periodically
Spark plugs running too hot
Install colder type spark plugs
Engine control module faulty
Replace
Engine lacks power
Spark plugs fouled
Clean
Fuel injectors defective
Replace
Mass Airflow Sensor or Intake
Airflow Sensor circuit defective
Correct or replace
Barometric Pressure (BARO)
Sensor or Barometric Pressure
Sensor circuit defective
Correct or replace
Engine Coolant Temperature Sensor
or Engine Coolant Temperature
Sensor circuit defective
Correct or replace
Engine Control Module faulty
Replace
Intake Air Temperature Sensor or
Intake Air Temperature Sensor
circuit defective
Correct or replace
Throttle Position Sensor or Throttle
Position Sensor circuit defective
Correct or replace
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