Great Falls tribune. [volume] (Great Falls, Mont.) 1921-current, 1922-12-31
Barney 0ldfeld sags:
SPARK PLUG TROUBLES.

tween the ends Of two wires. The
spark jumps this gap, as it does SO
imparting it's heat to the gas mixture,
thus exploding it. Simply stated, this
1s the function of the plug-to explode
the mixture by means of the heat of a
spark, but at the same time the plug
itself must be able to Withstand the
tremendous heat and pressure inside
the cylinder; it must not allow escape
Of the gas mixture, it must u%nfaiingly
transmit current so the gap will be
jumped and it must do this many thou
sands Of times q mile of running.
When one considers the work a. spark
plug has to do, it is surprising how
well and how long this little part re-
mains in service. Plug trouble today
Is not SO common as it was years ago,
and we have heard of plugs function
ing without any attention for as many
as 10000 miles.
There are hundreds of designs OF
plugs made of a variety of materials
and made in numerous shapes n
STYLES. It is easy to see how difficult
it is to design a plug to meet all the
conditions demanded Of it, yet the
modern spark plug does its work ad-
mirably well. / wish to describe in
this article the construction of plugs,
the way to install them properly, the
type to get and not to get, plug
troubles and how they may be
remedied.
Perfect Insulation Important
Since the end of the plug must in
troduce q gap into the combustion
chamber there must be two wires or
electrodes with their ends separated to
form the gap. One of these electrodes
which takes the current from the cable
or wire from the ignition device must
be perfectly insulated so no current
will leak out, while the other electrode
must be grounded in some way. ms
latter always is attached to the spark
nlug shell or the metal part which
screws into the cylinder, while the
other one, called the center electrode,
always is imbedded in an lnsuiator
made of porcelain, stone. mica, etc.
The insulator and the shell then muse
be Joined together to make a unit OF
the plug. and this is done either py
.cementing them together, forcing .neaf f
to compression tightness by means OF
n mt. etc. Of course, the two parts
must SO fit together that no mixture
escanes. and the usual way OF OBTAIN
inc This tightness is by introducing u
rasket or two between the parts: :,
Pings are made with open or closen
.nds hut certain engines only VIII
cnerate successfully with one type.
often a closed end plug gives trounie
With an engine which, operating Waen
open end plug, gives entlre sa's
ton. ar If +he
crorE Ming are the insulator and eiec..
trodes The former is usually mace Q,
m;ca ar porcelain so as to "lthslanu
+ha tremendous heat and also changes
- +emnerature without cracking. Por-
ceIain and various stone omposleIo -
ora nsed, but of course this type Is
more easily cracked han mica Doln
Nv the heat and BY a wrench WI
installing. These materials may pc usp
Ia combination in the same plug, Is
best form consisting OF an outer s, NJ
;ns1lator and an inner mica one 1ne
rnlv trouble with mica is that 1t is
1;ahle 10 absorb oil, but 1t the con-
struction is right this may be pre-
vented altogether. The one advantage
~ the combination types is That there
1s double protection, so that II one ID,
s.,,ator becomes broken the other Will
nrevent current leakage. In buying a
hing you cannot tell by looking at the
fnsulator whether it is good or nor,
because some cheap stone LOOKS JUST
like good material. The reliaolllty o.
the maker is the thing to consider.
Watch CfdCkeu tHSuidtotS
Electrodes must be Of such material
as not to be quickly affected by heat,
spreading and changing the gap SIZE;
or burning away altogether. Nickel
wire. or similar high heat resisting
wire usually is used, but the car owner
should take note of the thickness OF
the electrodes. Thick ones last longer
than those Of small diameter.
The commonest trouble with spark
plugs is caused by cracked insulators,
which then allow of current leakage.
causing a poor spark or none at all
ut the gap. Otter one cannot tell by
examining the outside whether the IN
~sulator is cracked, because the trouble
NAV be in the hidden portion. The only
safe way is either to dismantle the
Mug if it is not of the one-piece type
or test it by laying it on the cylinder
head with the plug cable attached. Then
by cranking the engine the gap may be
WATCHED for a good spark. Cracks,
except hidden ones, may at once be
noticed if the engine is operating In a
dark area; sparks will be seen on the
outside of the insulator.
Fouling is another plug trouble. Ihis
term refers to the carboniZation of the
electrode ends and bottom of the in
%sulator, resulting in a short circuit
6IUCe Tile CutICnt "a pass haoaSA
the carbon instead of jumping the gap
which offers greater resistance. The
carbon deposits in troublesome quantity
because oil is splashed On the plug. and
Il the plug is of the sort which retains
the oil carbon forms there. It is usual
to hook shape the ground e%lectrode SO
that oil will tend to flow away from
the al
When plugs become carbonized they
should be cleaned by immersing in
kerosene and then removing and scrap
ing off the carbon. The scraping may
be done with a knife, but care should
be taken not to roughen the parts as
this makes a good footing for more
carbon. When plug fouling persits the
cause should be gone into-probably
leaky piston rings, too much oil, too
thin an oil, worn OR pitted cylinders,
etc.
Don't Remove Plugs CareIessIy
The gap at the plug end must be
DrODerfy set. The uSlIa1 gan is Lao