Operation and Maintenance Manual for WP2.1C/WP3.9C Series Marine Diesel
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1. Camshaft timing gear 2. Idle gear 3. Injection pump gear
4. Oil pump gear 5. Oil pump driving gear 6.Crankshaft timing
The valves are opened and closed in certain timing events. They are driven by the
camshaft through tappets, push rods and rocker arms.
3.4 Crank-connecting Rod Mechanism
The crank-connecting rod mechanism is composed of the piston-connecting rod
assembly and crankshaft-flywheel assembly.
The piston-connecting rod assembly consists of the piston, compression rings, oil
scraper ring, piston pin, connecting rod, connecting rod bearings and connecting rod
bolts.
The crankshaft-flywheel assembly consists of the crankshaft, flywheel, crankshaft
timing gear and crankshaft pulley.
Two compression rings and one oil scraper ring are fitted into the piston. The first
compression ring is a keystone type ring. When the rings are fitted into their grooves,
their gaps should be apart from each other around the circumference of the piston.
Furthermore the oil scraper ring should be so placed that its gap is 90 degrees apart
from the pinhole centre around the circumference. The second compression ring
should have its top surface (marked with STD in the area near the gap) upward in
assembly. When checking the ring gap, place the ring into a cylinder liner and
measure it with a feeler gauge.
If the gap is too small, correct it by fine filing; if too large, replace the ring with a
new one.
When assembling the piston and connecting rod, heat the piston in hot oil to the
temperature of 100 to 120 degrees centigrade and then push the piston pin through
them.
The connecting rod and cap are machined and marked in
couples. They are not interchangeable. Two connecting rod bolts should be
tightened step by step in turn to reach the specified torque.
Before placing the piston and connecting rod assembly into the liner smear them
with a little clean oil. Make sure the intake valve pocket (the larger one of the two
pockets on the piston) is on the left side of the exhaust valve pocket viewed from the
injection pump side of the engine in assembly. When moving the piston and
connecting rod through the cylinder liner, be careful not to bruise the liner surface.
Fig. 5
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