DESCRIPTION
Turbocharger is mounted on the left side of engine. Turbocharger components include turbine and compressor impellers (wheels), impeller shaft, bearings, impeller housings and wastegate valve.
Pressure actuated wastegate prevents excessive intake boost pressure. If wastegate fails, an emergency relief valve releases excess pressure. Engine oil pressure provides constant lubrication to turbocharger assembly.
OPERATION
Turbine impeller of turbocharger is driven by exhaust gases expelled from cylinder combustion chambers. At idle, no pressurization of intake air takes place and engine operates like a normally aspirated engine.
With engine under partial load, throttle valve opens and more air/fuel mixture is drawn into combustion chambers. Speed and volume of exhaust gases also increase. Increased amount of exhaust gases turn turbine impeller at a higher RPM.
Compressor impeller turns at same RPM as turbine impeller because they are mounted to same shaft. Increased RPM of compressor impeller boosts pressure of intake air. With engine under full load, exhaust gases are at maximum pressure, which increases RPM of turbine and compressor impellers to an extremely high speed.
Exploded View of Isuzu Turbocharging System. Scheme 32
LOW ENGINE POWER
- Check for air leak at connection of compressor housing and suction hose/inlet tube, or inlet tube and intake manifold. Tighten or repair connections as needed.
- Check for exhaust leak at connection of turbine housing and exhaust manifold, and connecting tube or exhaust outlet. Correct connection or replace gasket if necessary.
- Check for stuck open bypass valve, stuck or damaged journal. Inspect for sludge on back of turbine wheel, or broken turbine wheel. If any of these conditions exist, replace turbocharger assembly.
OIL CONSUMPTION & BLUE SMOKE
Check for oil leak at outlet tube assembly and correct as needed. Check for leak at turbine compressor oil seal. Inspect for worn journal or bearings. If any of these problems are present replace turbocharger.
INSPECTION
Note. Replace turbocharger as an assembly if diagnosed as defective.
TURBINE & COMPRESSOR IMPELLERS
Inspect turbine and compressor impellers for cracks, clogging, deformity or other damage. Revolve impellers to be sure they turn freely without any abnormal noise or friction.
BY-PASS VALVE CONTROLLER
Check operation of by-pass valve controller by moving valve to make pressure gauge to controller. Apply 14.5" Hg with hand held pump. Pushrod should move as vacuum is applied. Disconnect wastegate controller pushrod. Move wastegate lever back and forth and check for binding or sticking.
REMOVAL
Remove heat shield and rubber hose to air cleaner. Remove control cable and hose between turbocharger and radiator. Disconnect oil delivery and return hose. Separate exhaust pipe and remove turbocharger assembly.
INSTALLATION
To install, reverse removal procedure. Replace gasket between turbocharger and exhaust manifold.