Cub Cadet Challenger 550, Service Manual

Page: 249 / 255

Troubleshooting
8‐6
marks in Step7, listen for pressure building inside the combustion chamber,
indicating that the piston is moving to TDC on its compression stroke. Second,
view the gauge on the leak down tester when turning the engine. As the piston
moves toward TDC on its compression stroke, compression building inside the
combustion chamber may cause the gauge needle to move slightly. If the
crankshaft is 360°off, these indicators will not be present.
Note:
The decompression mechanism will click loudly once during each
crankshaft revolution. This is normal.
• Use hex socket on the fan hub mounting bolt and turn the crankshaft clockwise
and align the TDC mark on the flywheel with the index mark on the left
crankcase cover
•
Remove the hex socket from the primary drive gear.
•
Perform the following to lock the transmission so the engine remains at TDC on
its compression stroke when performing the leak down test:
Warning:
Do not attempt to lock the engine by trying to use a tool to hold the Allen bolt on
the end of the crankshaft. Once the combustion chamber becomes pressurized,
any crankshaft movement can throw the tool away from the engine under
considerable force, attempting to hold the tool can cause serious injury. Engine
damage may also occur to the crankshaft or right crankcase cover. Lock the
engine as described in this procedure.
•
Turn the drive sprocket by hand and shift the transmission into top gear with the
shift lever.
•
Mount a holding tool or equivalent onto the fan hub. Use a wooden block and
clamp to hold the holding tool so it cannot move when the combustion
chamber becomes pressurized. Using a long breaker bar and securing it
against the engine frame is an example.
•
Check that the TDC marks are still aligned as described in Step7, if not, turn the
crankshaft as required, then relock the holding tool in position.
•
Remove the radiator cap and the oil filler cap.
• Perform a cylinder leak down test by applying air pressure to the combustion
chamber.
Follow the manufacturer’s instructions while reading the percent of leakage on the
gauge. Listen for air leaking while noting the following:
Note:
Because of play in the transmission gears, it is unlikely the engine will stay at
TDC on the first try. If the crankshaft turns, reposition the countershaft slightly
and then relock it in position with the holding tool. After several attempts, you
will get a feel of the transmission play and know what direction the countershaft
should be turned and locked.