Choosing the Right Glow Plug
from O.S. Engines - Model Aviation
Several factors influence
the use of the correct glow plug for your engine. Here are some guidelines:
• Cold plugs produce more power and may improve performance if your
engine runs hot. The downside is rougher idling and more difficulty in
• Fuel-air mix not only affects how your engine performs; it can also
have an impact on how long your plug lasts. If you run rich, it means that
you’re using more fuel than necessary for top performance. Modelers are
often advised to run rich during engine break-in, because it helps cool the
engine. However, running too rich can also cause an engine to bog down or
quit entirely. In addition, it also means that the glow element is being
exposed to more contaminants than necessary, which shortens plug life.
Running lean means that you’re using less fuel. “Leaning in” an engine has a
positive effect on performance. However, care is needed here, because
over-leaning an engine can harm it, by raising operating temperatures, and
burn up a plug [Tech Editor’s Note: More than the plug might be lost,
excessive leaning can ruin an engine!] before it’s time. Do not over lean!
Use the right glow plug. Follow the guidelines above.
Follow the proper break-in procedures.
Tune your engine carefully. Running too lean will make your engine “blow”
plugs more often. Proper tuning helps extend plug life.
Never touch the filament of a glow plug. Doing so can break the filament
and ruin a plug.
Don’t over tighten your plug. Tighten it until it’s just snug.
Be sure to shim your engine correctly. A plug that’s too close to the
piston can cause pre-detonation, which will quickly damage a glow plug.
Use only a glow starter or 1.5V battery to heat your plug. Otherwise, your
plug may burn out ahead of it’s time. Don’t be afraid to ask for help.
Experienced modelers have already “been there, done that.” Their experience
can save you time and money; and most are glad to help.
Glow plugs get very hot, enough to glow the filament red or white hot, and
removing a glow plug while power is applied can cause burning if appropriate
care is not taken. [Tech Editor’s Note: Removing the plug while it’s still
being “heated” strikes me as nearly impossible, since any attachment to the
plug, that would be doing the heating, must be removed so that you can have
access to remove the plug. The only other way to heat the plug is from the
combustion in the engine, so if you are handling the engine, it’s generally
a good thing to have stopped it running while you “fool” with it.] Special
caution must be taken while near fuel sources.
Some connectors for glow plugs can short circuit and damage batteries, or
cause them to explode. Batteries may get hot during the use of a glow plug.
This especially applies to homemade or nonstandard connectors.