New-York tribune., 1921-12-11
Widening of Spark Cap Will
Help to Overcome Skipping
Dirty lnterrupting Points and Breaking Down
of the Condenser Are Two of the Causes for
That Irritating Engine Knock or Sputter

ciate this often results In a man think
ing his ignition ia all right, when
there may be a brack in the insula-
t'on 80 small that it scarcely can be
seen with the naked eye when cleaning
the plug, or there may be a porous spot
in the porcelain, either of which would
leak current under compression. Many
manufacturers test the porcelain to
see If they leak, using n spark gap of
three-quarters of an inch under a high
voltage.
Short -Circuiting the Plug
II there is carbon on the porcelain,
the current very often will travel
through this under high compression,
because there is less resistance offered
by the carbon than by the spark gap.
1t short-circuits the plug and there
Is no Ignition. Yet when this same
plug is removed and tested in the open
air, there will be a good spark; the
resistance of the gap in the open air
would be less than the resistance of
coating. If, on testing plug in this
way there seems to be q good spark,
yet the, cylinder will not fire, clean
the plug thoroughly and try it out in
the cylinder. If it still does not fire,
try plug which you know is all right
and see if it fires. If it does, you may
know that the old plug leaks current
somehow and probably needs q new
porcelain.
1t Is common error with motorists
when cleaning spark plug to polish
up the points and call it q Job.
What really is required is to remove
all of the carbon, which IS fair con-
ductor of electricity, from the porce-
nd
the insulator again.
When battery ignition is used, skip
ylng at low engine speed may often be
overcome by changing the gap in the
lnterrupter points the same as in the
magnetic. The points ae usually set
Tor normal running speed, and when
trouble is experienced at either ex-
treme high Or low speed adjustment is
necessary.
The gap at the spark plug points
must be greater usually than when
magnetic Ignition is used, because the
spark given by battery systems is
naturally of less volume than thai
given by the magnetic. Therefore the
gap must be greater to intensity the
current as befoe described.
Keep Interrupter Points Clean
The interrupter points some times
become coated with an Insulating glaze
composed OF oxides and dirt hammered
by the action of the movable inter
rupter point, or hammer. The points
wlli have the appearance of being all
right; there will be no pits or points
nevertheless there may be enough in
sulating material there to keep the cur
rent from flowing and no spark will
occu in consequence. The points NAV
be cleaned by inserting very thin
file between the points when they are
open and then allowing them to close
on the file, being held together with
no more pressue than the spring exerts.
and working the file back and forth
until the glaze is removed 1t is nee
essary to have a fat suface that make
contact across the entie face, so that
care in using the file is needed and as
little metal as possible should be re-
moved.
The condenser is another point of
possible trouble. The condenser in
creases the volume of the spark about
twenty-five times. We often find that
a vey weak spark may be caused by
apartial breaking down of the con
deser, or occasionally to the fact that
1t is disconnected at the terminal
Condensers are usually hidden away SO
that the novice cannot lccate troubles
OF TINS nature, but an extensive spark
ing at the interrupter or vibrator
points, when they are clean, with a
very weak spark at the plug point
indicates that the condenser is not
working properly. When this sparkling
occurs have an expert examine the con
denser for trouble.