| Tweet |
Custom Search
|
|
|
||
 TM 55-1905-217-34
(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 " ut of time" due to an improperly assembled gear train, a
o
quick check can be made without having to remove the flywheel and flywheel housing by following the
procedure outlined below.
c. 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 cylinder head 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 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. 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.
(5) Select a dial indicator with .001 inch graduations and with a spindle movement of at least 1 inch.
Use suitable mounting attachments for the indicator so that it can be mounted over the injector hole in the
cylinder head. Provide an extension for the spindle of the indicator. The extension must be long enough to
contact the piston as it approaches its upper position.
(6) Mount the indicator over the injector hole and tighten mountings sufficiently to hold the indicator
rigid. The mounting leg may be threaded into the rocker cover stud; or, the stud may be removed from the
cylinder head and the leg threaded into the tapped hole, depending upon the length of the rod used in making
up the mounting attachments. Make sure that the spindle extension is free in the injector hole, does not bind,
and is free to travel its full 1 inch movement.
(7) Provide a suitable pointer and attach it to the crankshaft front cover or engine front end plate. The
pointer should extend over the vibration damper, or crankshaft pulley, whichever is used.
(8) Rotate the crankshaft in the direction of rotation slowly until the hand on the dial indicator just stops
moving.
(9) Rotate the crankshaft in the direction of rotation until the indicator hand just starts to move. Reset
dial to "O". Continue turning the crankshaft slowly until the indicator reading is .010 inch-then stop turning.
(10) Scribe a line on the damper (or crankshaft pulley) in line with the end of the pointer.
(11) Rotate the crankshaft opposite the direction of rotation slowly until the hand on the dial indicator
just stops moving.
(12) Rotate the crankshaft opposite the direction of rotation until the indicator hand just starts to move.
Reset dial to "O". Continue turning the crankshaft slowly until indicator reading is .010 inch-then stop turning.
(13) Scribe a second line on the vibration damper (or crankshaft pulley) in the same manner as in step
10.
(14) Scribe a third line halfway between the first two lines. This is positive top-dead-center. Remove
the indicator from the engine.
NOTE
Make certain that the crankshaft pulley retaining bolt is not loosened while turning
the crankshaft. The bolt must be tightened to 290-310 lb-ft torque if it becomes
loose.
(15) Install the injector assembly. Swing the injector and valve rocker arms back into position and install
the rocker arm brackets and tighten the bolts to 90-100 lb-ft torque. Adjust the valve clearance and time the
injector. Rotate the crankshaft until the exhaust valves in the selected cylinder are open.
(16) Install the dial indicator again so the spindle of the indicator rests on top of the injector follower.
Set the indicator dial to "O". Rotate the crankshaft slowly in the direction of rotation, and stop when the TDC
mark on the vibration damper or crankshaft pulley lines up with the pointer.
(17) Note the reading on the dial indicator and compare with the following: If the indicator reading is
.223 inch to .233 inch, the engine is in time; if the indicator reading is .188 inch to .204 inch, timing is one tooth
retarded; if the indicator reading is .249 inch to .257 inch, timing is one tooth advanced.
(18) After completing the timing check, remove the dial indicator. Remove the shipping caps from the
injector, and install the injector fuel
3-93
|
||
|
||
