Engine Maintenance
74
Engine Thermostat
For the best engine operation, use a 180 F (82 C)
thermostat year round.
Engine Fuel System
The fuel system used on the Thermo King diesel
engine is a high pressure system used in
conjunction with a prechamber.
The components of the fuel system are:
• Fuel tank (may be the truck fuel tank)
• Electric Fuel pump
• Fuel filter
• Injection pump
• Injection nozzles.
A 10 psig (69 kPa) electric fuel pump pulls fuel
from the fuel tank through a fuel pump filter, then
pushes it to the fuel filter, and to the injection
pump. The prefilter is designed for diesel fuel and
is the only type that should be used.
The injection pump plungers are activated by its
own gear driven camshaft. The governor sleeve
and weight assembly is mounted on the end of the
camshaft with governor’s speed requirements
being relayed to the injection pump through a
linkage arrangement located in the front timing
cover. The injection pump raises the pressure of
the fuel and meters the correct amount of fuel to
the nozzle at the correct time. The increased fuel
pressure will lift the spring loaded nozzle to admit
fuel into the combustion chamber.
The fuel system is relatively trouble free, and if
properly maintained will usually not require major
service repairs between engine overhauls.
The most common cause of fuel system problems
is contamination. It cannot be stressed enough that
the fuel must be clean, fuel tanks must be free
from contaminants, and the fuel filter must be
changed regularly. Any time that the fuel system
is opened up, all possible precautions must be
taken to keep dirt from entering the system. This
means all fuel lines should be capped when open.
The work should be done in a relatively clean
area, if possible, and the work should be
completed in the shortest time possible.
Thermo King recommends that any major
injection pump or nozzle repairs be done by a
quality diesel injection service specialty shop. The
investment in equipment and facilities to service
these components is quite high. Therefore, this
equipment is not found in most repair shops.
The following procedures can be done under field
conditions:
• Bleeding air from the fuel system.
• Maintenance involving the fuel tank and filter
system.
• Speed and governor adjustments.
• Electric transfer pump replacement or repair
(10 psig [69 kPa] pump with diesel filter).
• Injection line replacement.
1. Thermostat Housing
2. Gasket
3. Thermostat
4. Water Pump
Figure 33: Water Pump Assembly and Thermostat
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