The Aberdeen weekly., 1919-03-28

prepared by the United States Depart
ment Of Agriculture.)
With all engines using spark plugs
ii is comparatively easy to ascertain
whether the ignition system is work
ing properly. Simply remove plug
and ascertain that the porcelain or
other insulating material on the inside
of the plug is not coated with carbon
and that the points are properly
spaced. One thirty-second of an inch
IS about the right space for most sys-
TENS where dry battery is used. This
is about equal TO the thickness of
worn dime. A wider gap will often
make starting difficult, especially when
the spark is rather weak or where a
high tension magnetic is used. In the
latter case the best results will often
be obtained when the gap is not more
.han one-fortieth- or even one-fiftieth
of an inch. Then re;attach the wire
and lay the plug so that the metal
base touches the engine casting, while
the end of the wire and the metal
tip of the plug are at least half an
inch from any metal part connected
with the engine and in such Il posi-
tion that the points are visible while
cranking the engine. Then turn the
engine over few times Cat least as
many times as there are cylinders)
and note whether spark jumps across
the space between the points. 1t is
Eot sufficient, however, merely to as
certain if there is Spark-it must
be hot enough to fire the compressed
charge in the cylinder. 1t is, of course,
difficult 70 tell by merely looking at
1t whether the spark is hot enough
or not, but If it is heavy blue, OF
bluiSh-white, or a fiat" yellow one
looking like a small flame, it is prob
ably all right. If very thin and green
ish or showing red. the chances are
II is TOO weak to fire the charge. One
may familiarize himself with the as
pect of Il good spark as follows:
Finding Good Spark.
While the motor is in satisfactory
running condition loosen the nut on
the top of the plug while the engine is
stopped so it Will be easy to remove
the wire from the plug after the en-
gine is started. Then start the en-
gine and, by taking hold of the wire
where il is covered with insulation,
move the end of the wire very slowly
away from the center of the plug and
watch the spark jump. closely observ-
ing its color and thickness.
1t is also well to note the distance
the spark will jump. yet not advisable
70 force it to jump too great Il gap
nor should the end of the wire be al
lowed to rest in a position where the
spark cannot jump TO the plug or the
engine while the engine is running, as
this tends to break down the inSula-
ton of the coil. In the case Of high
tension magnetos there is no danger
In this respect, as they are fitted with
a safety spark gap which the spark
will jump, if for any reason the circuit
Is broken elsewhere.
knowledge of just how much of a
spark one should obtain with each |
kind of ignition system is frequently |
of great value in locating trouble, and |
everyone who operates gas engine |
should make the abOve-described tests
while the engine is in good order. IF |
the looks of a good spark to tell by |
mere observation whether it is hot |
enough, rough test may be made /
as follows: Place thin piece of |
dry cardboard, such as an ordinary Wis
iting card, or three or four tliicknesses i
of dry newspaper, between the points
of the plug while it is lying on the |
engine in the position first mentioned. |
then crank the engine. A good spark
will jump through these, leaving
tiny hole. A spark which Will not do
this is too weak to jump the spark
gap in the cylinder under compress
sion.
If the engine is equipped with a !
which an igniter block is used instead
Of a spark plug, ii can be ascertaned
easily whether the entire system, with
the exception of the igniter block, is
In good shape by disconnecting the
wire from the igniter block and snap
ping it across the corner of the en-
yine casting or the end of the other
wire leading from the coil. But even
though this gives good spark II
does not necessarily mean that the
spark is given in the cylinder when
the engine is turned over. II may
be that the points of the electrodes
inside the cylinder do not touch each
)ther when they should or are not
making a good contact, because car
bon. OIL dirt, etc. have accumulated
between these points. Therefore, If
1 good spark occurs when the wire IS
snapped across part of the engine,
rank the engine until the movable
,lectrode is released and allowed to
1y back.