Testing For Overhaul - Westerbeke 8.0KW-60Hz Service Manual

TESTING FOR OVERHAUL
HOW TO DETERMINE ENGINE OVERHAUL PERIOD
Cause of Low Compression
Generally, the time at which an engine should be overhauled
is detennined by various conditions such as lowered engine
power output, decreased compression pressure, and increased
fuel and oil consumption. The lowered engine power output
is not necessarily due to trouble with the engine itself, but is
sometimes caused by injector nozzle wear
Or
injection pump
wear. The decrease in compression pressure is caused by
many factors. It is, therefore, necessary to detennine a cause
or causes on the basis of data produced
by
periodic
inspection and maintenance. Oil analysis on a seasonal basis
is a good means of monitoring engine internal wear. When
caused by worn cylinders or piston rings, the following
symptoms will occur:
1 Low engine power output
2 Increased fuel consumption
3 Increased oil consumption
4 Hard engine starting
5 Noisy engine operation
These symptoms often appear together. Symptoms 2 and 4
can result also from excessive fuel injection, improper
injec~
tion timing, and wear of the injectors. They are caused also
by defective electrical devices such as the battery, alternator,
starter and glow plugs. Therefore it is desirable to judge the
optimum engine overhaul time by the lowered compression
pressure caused by worn cylinders and pistons plus increased
oil consumption. Satisfactory combustion is obtained only
under sufficient compression pressure. If an engine lacks
compression pressure, incomplete combustion of fuel will
take place even if other parts of the engine are operating
properly. To deteITI1ine the period of engine overhaul, it is
important to measure the engine compression pressure regu-
larly. At the same time, the engine speed at which the mea-
surement of compression pressure is made should be checked
because the compression pressure varies with engine rpm.
The engine rpm can be measured at the front end of the
crankshaft.
NOTE:
To test engine compression see the
ENGINE
ADJUSTMENT
section of this manuaL
ASSEMBLY
L
Wash all parts, except for oil seals, O-rings, rubber sheets,
etc., with cleaning solvent and dry them with pressure air.
2. Always use tools that are in good condition and be sure
you understand how to use them before performing any
job.
3. Use only good quality lubricants. Be sure to apply a coat
of oil, grease or sealant to parts as specified ..
4. Be sure to use a torque wrench to tighten parts for which
torques are specified.
5. Ant time the engine is assembled. new gaskets and
O-rings must be installed.
OVERHAUL CONDITIONS
Compression pressure tends to increase a little in a new
engine until piston rings and valve seats have been broken in.
Thereafter, it decreases gradually with the progress of wear
of these parts.
When decrease of compression pressure reaches the repair
limit, the engine must be overhauled.
The engine requires overhaul when oil consumption is high,
blowby evident, and compression values are at minimum or
below. Engine compression should be 30 kg!cm', 427 psi at
290 rpm. The maximum difference betvveen cylinders must
not exceed 10%.
DISASSEMBLY
1.
Before disassembly and cleaning, carefully check for
defects which cannot be found after disassembly and
cleaning.
2, Drain water, fuel and oil before disassembly.
3. Clean or wash the engine exterior.
4. Do not remove or disassemble the parts that require no
disassembly.
5. Perform disassembly in a proper order using proper tools.
Keep disassembled parts in order. Apply oil when neces-
sary. Take special care to keep the fuel system parts from
intrusion of dust and dirt.
6. Parts must be restored to their respective components from
which they were removed at disassembly. This means that all
parts must be set aside separately in groups, each marked for
its component, so that the same combination or set can be
reproduced at assembly.
7. Pay attention to marks on assemblies, components and
parts for their positions or directions. Put on marks, if
necessary, to aid assembly ..
8.
Carefully check each part or component fore any sign of
faulty condition during removal or cleaning. The part will
tell you how it acted or what was abnormal about it more
accurately during removal or cleaning.
ALTERNATOR INSPECTION
When rebuilding the engine, the alternator should be cleaned
and inspected. The housing can be wiped off with a solvent
and the alternator tenninal studs should be cleaned with a
wire brush. Make certain the studs are tight and clean the
wiring connections that connect to the wiring harness.
Turn the rotor pulley by hand. It should tum smoothly.
Depending on when the alternator was last serviced, the
brushes may need replacing. If the alternator is at all suspect,
send it to a service shop for testing and overhaul.
For additional information on alternators refer to the
ALTERNATOR TROUBLESHOOTING
and
MANDO
SERVICE
in this manual.
Engines & Generators
9