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Page Title:
Section XVIII. MAINTENANCE OF ENGINE |
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 TM 10-3930-632-12
Section XVIII. MAINTENANCE OF ENGINE
4-62. General
The fork lift truck is powered by a four-cylinder, internal
combustion, water-cooled, L-head, gasoline engine. A
combustible mixture of fuel and air is delivered by the
carburetor through the manifold and intake valves to the
combustion chambers, where it is ignited by an electrical
spark across the electrodes of the spark plugs. The
burning mixture of fuel and air causes a heat rise in the
combustion chamber.
This heat rise causes an
expansion of the gasses in the combustion chamber that
forces the pistons downward in the cylinders. The
motion of the pistons causes rotation of the crankshaft.
The burned mixture and hot gasses are passed through
the exhaust valves to the exhaust manifold. Heat left in
the engine is transferred to the radiator by the coolant in
the cooling system. The exhaust and intake valves are
Figure 4-44. Checking Engine Compression
operated by the camshaft which is geared to the
crankshaft. Moving parts of the engine are pressure-
(5) Compression readings above 110 PSI,
lubricated by an oil pump driven off the camshaft.
and within 10 PSI of each other are normal. If readings
are below 110 PSI or are irregular, the valves or valve
4-63. Testing
seats are burned, the piston rings are worn, or there are
a. Compression Test.
other internal engine problems.
(1) Test the battery (para 4-37). If the
(6) If compression fails to fall within the
battery is not fully charged, replace it with a fully
required range, report to direct or general support
charged battery.
maintenance personnel.
(2) Start the engine and allow it to run until
it reaches operating temperature (160--180F), then shut
4-64. Engine Adjustment
off the engine.
Engine adjustments are restricted to engine timing,
(3) Clean around the spark plug ports with
valve lash, carburetor and governor adjustments.
compressed air and a cloth dampened in an approved
Procedures for these adjustments are outlined in the
cleaning solvent. Remove the spark plugs.
applicable sections below.
(4) Hold a compression gage in a spark
a. Ignition Timing Test and Adjustment.
plug port as shown in figure 4-44. Crank the engine with
(1) Set distributor point contact gap (para
the starting motor until the highest gage reading is
reached. Record the reading. Repeat this process at
(2) Remove spark plug No. 1 nearest the
each of the remaining spark plug ports. The firing order
radiator. Place a finger or thumb over the spark plug
is 1-3-4-2. Reinstall spark plug.
port. Crank the engine with the starting motor until air is
forced out of the no. 1 cylinder past the thumb or finger
plugging the port. The firing order is 1-3-4-2.
4-60
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