ENGINE
a brand-new engine should be capable
of
devel-
oping)
is
based on a specific speed
of
engine
cranking.
Nozzle tester
Compression pressure test -
how
to
measure
compression pressure
(1)
Remove the preheater plug
of
the cylinder
to
be checked.
(2)
Run
the pressure-gauge
adaptor
into
the
threaded hole
just
vacated by
the
plug, and
tighten the adaptor good and hard. Tie the
gauge line, complete with the compression
pressure gauge, into
the
adaptor. The gauge
is
now rigged up.
(3) Start cranking the engine with the speed
control lever fully pushed in so
that
no fuel
oil will be injected and read the engine
speed just when
the
cranking speed has
reached a steady level. Read the pressure
gauge indication: this reading
is
the "com-
pression" pressure
of
that
cylinder.
(4) Carry
out
the foregoing steps
on
the next
cylinder to read its "compression" pressure.
[NOTE]
Taking a reading only on
one
cylinder
and assuming the
other
cylinders
to
produce the same pressure reading - this
is
a practice likely
to
result in an unwise
decision. In the present engine, take
three readings, one
on
each cylinder
.•
2-52
Engine diagnosis
on
the
basis
of
compression
pressure readings
(a) Compression pressure
of
a brand-new
engine could be slightly increased
as
the
piston rings, valve seats, etc. wear in.
As
the engine parts wear down after
"run-in"
period, compression pressure lowers gradu-
ally.
(b)
If
the readings are down
to
the limit (repair
limit), the engine should be overhauled.
Measuring "compression" pressure
Engine diagnosis
on
the basis
of
oil
consumption
Another
yardstick
is
oil consumption:
if
the current oil consumption
is
higher by more
than 50% than the normal consumption, the
engine
is
probably in need
of
overhauling.
General working rules
on
disassembling and
reassembling steps
(a) Cleanliness
is
absolutely essential for suc-
cessful work, with respect to
the
place
of
work, shop facilities such
as
benches and
fixtures, the engine parts handled, the
tools and materials.
(b) Use
of
right kinds
of
tools
is
another
essential.
(c) Before disassembling the engine, drain
water, lube oil and fuel completely. Check
oil for contamination. Also check the
qualities.of the oil and fuel.
f
£
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