Engine Maintenance
86
Engine Fuel System
The fuel system used on the Thermo King TK
3.74 diesel 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 prefilter, then pushes
it to the fuel filter, and to the injection pump.
The injection pump plungers are activated by an
extension on the engine camshaft. The governor
sleeve and weight assembly is mounted on the end
of the crankshaft 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.
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