Engine Adjustments; Measuring Compression; Belt Adjustment - Westerbeke 12C-TWO Operator's Manual

ENGINE ADJUSTMENTS
ENGINE COMPRESSION
Check the engine's compression pressure at 500 and 1250
operating hours or whenever engine performance is reduced.
Remove each glow plug and check each cylinder's
compression pressure. The engine's cranking speed is
at 280 rpm.
MEASURING COMPRESSION
Check the compression pressure. To do this warm the engine,
remove ail fuel injectors, or glow plugs, disconnect the fuel
shut-off solenoid wire, and install a compression adapter in
the injector hole or glow plug hole. Connect a compression
tester on the adapter and crank the engine with the starter
motor until the pressure reaches a maximum value. Repeat
this process for each cylinder. Look for cylinders with dra-
matically (at least 20%) lower compression than the average
of the others. Compression pressure should not differ by
more than 35.5 psi (2.5 kg/cm
2 )
at 280 rpm.
If a weak cylinder is flanked by healthy cylinder, the problem
is either valve or piston related. Check the valve clearances
for the weak cylinder, adjust as needed and test again. If the
cylinder is still low, apply a small amount of oil into the
cylinder to seal the rings and repeat the test. If compression
comes up - the rings are faulty.
Abnormally high readings on all cylinders indicates heavy
carbon accumulations, a condition that might be
accompanied by high pressures and noise.
NOTE: In case of severe vibrations and detonation noise, the
cause may be fuel injector problems, see FUEL INJEC-
TORS.
Poor fuel quality, contaminates and loss of positive
fuel pressure to the injection pump
will
result in injector
faults.
When re-installing the glow plugs use anti-seize compound.
COMPRESSION VALUES
STANDARD (AT 280 RPM) 398.16 PSI (28Kg/cm')
MINIMUM (AT 280 RPM) 355.5 PSI
(25Kg/cm'~
MAXIMUM ACCEPTABLE DIFFERENCE BETWEEN 35.5 PSI (2.5 Kg/em''
32
DRIVE BELT ADJUSTMENT
Excessive drive belt tension can cause rapid wear of the belt
and reduce the service life of the fresh water pump's bearing.
A slack belt or the presence of oil on the belt can cause belt
slipping, resulting in high operating temperatures.
The drive belt is properly adjusted if the belt can be
deflected no less than 3/8 inch (lOmm) and no more than 112
inch (12mm) as the belt is depressed with the thumb at the
midpoint between U'le two pulleys on the longest span of the
beli. A spare belt or beltS should always be carried on board.
A
WARNING:
Never attempt
to
check or adjust the
drive belt's tension while the engine is In operation.
Adjusting Belt Tension
1.
Loosen the alternator pivot bolt.
2.
Loosen the alternator adjusting bolt.
3.
With the alternator loose, swing it outward until the drive
belt is tensioned correctly.
4.
Tighten both bolts.
5.
Check the tension again after the engine has been in
operation.
GLOW PLUGS
To inspect the plug, remove the electrical terminal connections,
then unscrew or unclamp each plug from the cylinder head.
Thoroughly clean each plug's tip and threads with a soft brush
and cleaning solution to remove all the carbon and oil deposits.
While cleaning, examine the tip for wear and bum erosion; if it
has eroded too much, replace the plug.
An accurate way to test glow plugs is with an ohmmeter.
Touch one prod to the glow plug's wire connection, and the
other to the body of the glow plug, as shown. A good glow
plug will have a 0.90 ohm resistance. This method can be used
with the plug in or out of the engine. You can also use an
ammeter to test the power drain (12-13 amps per plug)
Re-install the plugs in the engine and test them again. The
plugs should get very hot (at the terminal end) within 7 to 15
seconds. If the plugs don't heat up quickly, check for a short
circuit. When reinstalling the glow plugs, use anti-seize
compound on the threads.