Isuzu 4JA1 Workshop Manual page 509

Checks
Air Intake System Checks
Exhaust System Checks
Engine Mechanical Check
Additional Checks
Excessive Smoke (White Smoke)
Checks
DIFINITION:White smoke under load, idle or start up hot or cold.
Preliminary Check
Sensor Check
Fuel System Checks
Inspect the air intake system for the following conditions.
• Inspect the air cleaner and air intake ducts for a restriction, holes, or leaks.
• Inspect for a restriction or leak in the intercooler.
• Inspect for a restriction in the turbocharger inlet duct.
• Inspect for a restriction or deposit in the intake throttle bore.
• Inspect for a restriction or leak in the intake manifold.
• Inspect for a restriction or damage at MAF sensor.
• Inspect for a worn or damaged turbocharger turbine wheel, shaft or compressor
wheel. Refer to turbocharger inspection in the Engine Mechanical section.
Inspect the exhaust system for a possible restriction. Refer to the Exhaust System
section.
• Inspect for a restriction in the catalytic converter or exhaust pipes.
Inspect the engine mechanical for the following conditions. Refer to the Engine
Mechanical section.
• Inspect for poor cylinder compression. Proper compression is more than 2100 kPa
(309 psi).
• Inspect for incorrect basic engine parts such as camshaft, cylinder head, pistons,
etc.
• Inspect for any excessive oil entering combustion chamber.
• Improper mechanical timing
• Improper valve gap
• Broken or weak valve springs
• Worn camshaft lobes
• Inspect the EGR system operating correctly.
• Inspect the excessive blow-by gasses.
• Inspect the scan tool Data List in this section.
• Ensure the vehicle has an actual problem.
• Inspect the engine control module (ECM) and fuel injection pump control unit (PCU)
grounds for being clean, tight, and in their proper locations.
• Inspect the fuel quality (cetane index).
• Inspect the Service Bulletins for ECM software updates.
Inspect the engine control sensors for the following conditions. Refer to the scan tool
Data List in this section.
• Use the scan tool to compare the Engine Coolant Temperature (ECT) with the Intake
Air Temperature (IAT) and Fuel Temperature (FT) on a cold engine condition. If the
difference among temperature reading is more than 5°C (9°F) on a cold engine,
check for high resistance on the low reference circuit and signal circuit or for a
skewed sensor.
Notice: The mass air flow (MAF) sensor is heated and as a result the IAT sensor may
indicate a higher than normal intake air temperature if the ignition switch is being ON.
FT sensor is internal to the PCU and it is part of the fuel injection pump assembly.
• Inspect the crankshaft position (CKP) sensor is tight and the flywheel circumference
is not damaged.
Inspect the fuel system for the following conditions. Refer to the Fuel System section.
• Inspect the fuel injection nozzle(s) for proper splay condition or operating pressure.
Notice: Only first stage of operating pressure can be checked.
• Inspect the timing device operating correctly. Observe the Actual Injection Timing
parameter with the scan tool while running the engine. The Actual Injection Timing
parameter must follow the Desired Injection Timing within 2°CA on each engine
speed. Engine idle > around 2000 RPM> around 3000 RPM. If not, inspect the fuel
system restriction, air in the fuel or fuel injection pump operation.
Engine Control System (4JH1) 6E-255
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