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Question concerning glow plugs

Old 10-03-2002, 01:46 PM
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Blackie
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Default Question concerning glow plugs

I would like to know that even if I am glowing red on the plug by way of indicator and or by way of checking with a none metered igniter with a visual. Does that necessarily mean that the plug is good?

And if not please explain the reasons.

Thanks
Randy
Old 10-03-2002, 04:49 PM
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Flyboy Dave
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Default Does that necessarily mean that the plug is good?

Not always....the indicator light or the little meter on
the glow starter will show you that you still have
continuity ( the little coil wire is not broken ), and
current flow through the wire. It might appear to be
glowing red at a glance, but the engine may still not
run right.

Sometimes during a lean run....the little coil inside
the plug will overheat, and will "warp" out of shape.
That part of the warped ( or bent ) coil will be touching
the inside of the plug, and will not be glowing red.
That means your only getting about half the heat out
of the plug that's needed to run the engine properly.

If your motor isn't running properly....kinda spitting
and sputtering....won't idle for more that a few seconds,
dies out in flight for no reason.....have a real close look at
that plug and see if the coil is still nice and round. If
it looks like it's bent, hook the glow to it and see if
it's glowing red from top to bottom.

Hope this helps....Dave.
Old 10-03-2002, 05:09 PM
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Default Question concerning glow plugs

Dave, thanks for the help.

Here's what I have.

I have an OS FS 120 pump in which starts and idles just fine but every time I throttle up it sputters then dies no matter what the needle adjustment is set at.

I have hooked up a glow started to the plug outside of the engine and I did get a red glow but as you stated that does not mean its a good plug. The plug is the type F but it seems that all the tails are telling me that the plug is bad.

Now on its first startup last night it ran great in the pits got 9k RPM with a 15X8 Prop but once I reached the runway and started a throttle up thats when it all started, I could not keep it running to save my life.

Engine is inverted.

Thanks
Randy
Old 10-03-2002, 05:38 PM
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Flyboy Dave
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Default Blackie....I've been there too.

I had an O.S. .90 4-Stroke ( inverted ) that started acting
up like that. Stick with those plugs, nothing works better.

I set the idle screw, and it would sit there and idle great,
all darn day....but try to give throttle....that sucker would
die right out, and was drivin' me nuts. Tried different
plugs, fuel, ect....nothing helped.

Here's what I found....the screws on the carb, and intake
manifold had begun to loosen ( new motor ), and it had
developed a small air leak. I had opened (and richened)
the low-end screw to compensate, and had great idle.
But it was TOO RICH to transition up off idle, and the
engine would die.

The 4-strokes are fussier about needle settings. The
2-stroke will usually run sloppy rich, no matter what.
When the motor kept "bogging out" and dieing out
coming off idle...I figured it was too lean....( like a
2-stroke ) and kept richening it up. It made it worse.

So the bottom line was....If it idles ok, but wont take
throttle...you might have to lean out the idle screw.

Hope this helps. If you have a long distance from the
pits to the flight-line...most guys use an on-board
glow system to avoid the dreaded "flame-out".
Old 10-04-2002, 05:47 PM
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HITNDIRT
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Default Question concerning glow plugs

something else on the plug.
if you look at the coils, they are in a coil and not smashed, but looking at the wire it should look clean.
some plugs that last a while in an engine and then the engine starts acting-up the plug went bad, but the coils are still in the correct shape. but looking at the wire you wouldsee the wire is "rough" like it was sanded, if you know what i mean,
the wire lost its coating and not holding the heat correctly. if usually only seen the hight quality(os, etc) last this long. but replacing with a new plug, even temporarly , diaganois this problem quikly.

just a thought?
Old 10-04-2002, 06:18 PM
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Blackie
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Default Question concerning glow plugs

As far as the on board glow starter, I had one on it set at a 1/3 throttle. I just removed it last night, going to try and run with out the onboard. I had purchased one from a co-member which supplyed its own battery. I found that I was only getting one flight before I had to charge the 1.2 volt battery so I said the heck with this.

Others have told me that I should be fine without it.

Thanks for all the help

Randy

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