Quantcast ENGINE TIMING - MAINTENANCE INSTRUCTIONS

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TM 55-1905-220-14-6
3-166.2.
ENGINE TIMING - MAINTENANCE INSTRUCTIONS (Continued).
a. General
(1) The correct relationship between the crankshaft and camshaft must be maintained to properly control
fuel injection and the opening and closing of the exhaust valves.
(2) The crankshaft timing gear can be mounted in only one position due to one attaching bolt hole being
offset. The camshaft gear can also be mounted in only one position as a result of the location of the keyway
relative to the cams. Therefore, when the engine is properly timed, the markings on the various gears will
match as shown.
(3) An engine which is "out of time" may result in pre-ignition, uneven running and a loss of power.
(4) When an engine is suspected of being out of time, due to an improperly assembled gear train, a
quick check can be made without having to remove the flywheel and flywheel housing by following the
procedure outlined below.
b. Checking Engine Timing
Access to the vibration damper or crankshaft pulley, to mark the top-dead-center position of the
selected piston, and to the front end of the crankshaft or flywheel for barring the engine over, is necessary in
performing the timing check. Then, proceed as follows:
(1) Remove the valve rocker cover.
(2) Select any cylinder for the timing check - it is suggested that a cylinder adjacent to one of the cylinder
head cover studs be chosen since the stud may be used for mounting a dial indicator.
(3) Remove the fuel lines (at the cylinder selected) and install shipping caps on the injector fuel fittings to
prevent the entry of dirt. Make sure that the valve and injector rocker arms are all in the "UP" position.
Then, remove the rocker shaft bracket bolts and swing the rocker arm assemblies back out of the way.
Remove the injector assembly.
(4) Carefully place (do not drop) a rod approximately 12 inches long through the injector hole and on top of
the piston.
(5) With the throttle in the NO FUEL position, turn the crankshaft slowly in the direction of rotation of the
engine, and stop when the rod reaches the end of its upward travel. Remove the rod and turn the
crankshaft opposite the direction of rotation between 1/16 and 1/8 of a turn.
3-2795


 


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