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 determlned by various conditions such as lowered engine
power outpu~ decreased compression pressure, and increased
fuel and oil consumption. The lowered engine power output
is not necessarily due to trouble with the engine iiself, 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 determlne 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 wom cylinders or piston rings, the following
symptoms will occur:
1 Low engine power ontput
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 mjection, improper injec-
tion timing, and wear of plugs and nozzles. 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 warn cylinders and pistons
plus increased oil consumption. Satisfactory combustion is
obtained ouly under sufficient compression pressure. If an
eugine lacks· compression pressure, incomplete combustion
of fuel will take place even if other parts of the engine are
operating properly. To determlne the period of engine over-
haul, it is important to measure the engine compression
pressure regularly. At the same time, the engine speed at
which the measurement 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
1. 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 nnderstand how to use them before perfonning 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
a-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 evideut, and compression values are at minimum or
below. Engine compression should be 30 kglcm', 427 psi at
290 rpm. Tlje maximum difference between cylinders must
not exceed IO%.
Minimum compression of 384 psi (27 kglcm') is an indication
for overhaul.
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
necessary. Take special care to keep the fuel system parts
from intrasion 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 abnonnal about it more
accurately during removal or cleaning.
OVERHAUL CONDITIONS
When rebuilding the engine, the alternator should be cleaned
and inspected. The housing can be wiped off with a solvent
and the altemator termlnal 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 in this manual.
-.,.y:
WESTERBEKE
Engines & Generators
9
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