| |
Today's
glow plugs, whether it be brand x or y they are
all well made products, and they should give you
good service. Although the life of a glow plug is
unpredictable, you should reasonably expect a dozen
or more runs out of one. If you have a motor which
seems to eat glow plugs, the probability is that
it is suffering from one of the following three
causes.
Overheating
A glow plug coil will melt if it gets too hot. Reasons
why this happens vary. Sometimes the combination
of running a motor wide open with a lean setting
before you take the glow plug heater off is too
much for the element. When a glow plug fails due
to overheating, the end of the element wire has
a tear drop shape. Unless you have very unusual
eyes, you cannot detect this without the aid of
a microscope or magnifying glass.
Vibration
If the engine is not rigidly mounted and can move
around very much, the element is shaken from side
to side with tremendous "G" forces. This
literally fatigues the metal until it breaks. The
only solution is to increase the rigidity of your
engine mount.
Shock Wave
Most model engines use a steel or brass liner mounted
on top of a cast aluminum case. As the engine gets
older, the liner flange works its way down into
the case and lowers the head with it. When the piston
clearance gets down to about .010, air is forced
out of the squish band area with supersonic velocity
and the action on the glow plug element is like
when a jet plane zooms over your house and knocks
out the windows. The cure here is to raise the head
with another head gasket.
Less often, reasons why glow plugs sometimes fail
are:
Cranking the engine when it is flooded. This sprays
raw fuel onto the plug and the droplets beat the
element over to the side of the housing where it
shorts out.
Another problem that occasionally occurs is that
motors sometime take to wearing abnormally, such
as a cracked crankshaft chewing metal out of the
bearing, or a connecting rod that is chewing metal.
Of course, when this metal goes up and deposits
on the plug element, the plug burns out.
|
|
