Inspect the nozzle rings closely for cracks. If the
nozzle rings are cracked or if the vanes are bent,
damaged, or burnt thin, replace them.
If you see signs of wear or distortion during the
inspection of the piston ring seals, discard and replace
them with new ring seals.
Inspect the turbocharger main casing for cracks in
the oil passages, cap screw bosses, and so forth. Also,
check the casing for bearing bore wear. If it exceeds the
limits allowed by the manufacturer, the bearing bore
may be reworked to permit oversize, outer diameter
Check the oil orifices plug for stripped or distorted
threads. Install a new plug if necessary.
The rotor assembly, which consists of a turbine
wheel, thrust washer, and locknut, is an accurately
balanced assembly. Therefore, if any one of the above
parts is replaced as a result of your inspection, the
assembly must be rebalanced according to the
When inspecting the semifloating bearing, measure
both the outside and inside diameters of the bearing. If
either diameter is worn beyond limits allowed by the
manufacturer, replace the bearing.
The front covers that are deeply scored from contact
with the compressor wheel cannot be reused. Slight
scratches or nicks only can be smoothed out with a fine
emery cloth and the covers reused. Cracked covers,
however, cannot be reused and must be replaced with
All cap screws, lock washers, and plain washers
should be cleaned and reused unless they are damaged.
Reassembly and Installation
After inspection of the turbocharger component
parts and replacement of damaged or worn parts,
reassemble the turbocharger as prescribed by the
manufacturers maintenance and repair manuals.
Close off all openings in the turbocharger
immediately after reassembly to keep out abrasive
material before you mount it on the engine.
Turbochargers can be mounted on the engine in
many different positions. Always locate the oil outlet at
least 45 degrees below the turbocharger horizontal
center line when the unit is in the operating position.
COLD STARTING DEVICES
Gasoline and diesel fuel engines are difficult to start
in cold weather. They are difficult to start because of the
low volatility of the fuel. In this section, the most
common cold starting devices for gasoline and diesel
fuel injection systems are discussed.
GASOLINE FUEL INJECTION COLD
Gasoline fuel injection systems may have a
cold-start injector (fig. 5-39) screwed directly into the
air intake manifold. This fuel injector will introduce
additional fuel into the intake manifold for cold starts
and initial cold engine operation. Other gasoline fuel
injection systems have a coolant sensor called a
thermistor (fig. 5-2). This sensor changes the electrical
resistance with the changes in the coolant temperature.
The lower the coolant temperature, the higher the
resistance. The electronic control module (ECM)
provides a low voltage signal to the thermistor and
monitors the return voltage value. A lower value means
a warm engine, a higher value means a cold engine. The
ECM then knows when the engine is cold and when to
provide a richer fuel mixture for cold starts and initial
DIESEL ENGINE INJECTION COLD
The most common cold starting system for diesel
engines is the glow plug system. This is an electrically
operated system used to heat the combustion chamber
Figure 5-39.-Typical cold-start injector mounted on the intake