millertym2000

My Feedback: (4)

while flying yesterday my OS 46 FX. dead sticked. I brought it in and tried to restart it. It started but when I started to give throttle to take off it died. Did this twice. Today I tried to retune the engine thinking that was my problem, after about a hour and lots of curse words[:@] My dad said " try a new glow plug" with the old plug the engine will start and run fine till I pull the glow warmer. If the plane is at a slow idle it would die as soon as I pulled the plug. but I could idle up and it would run a while, then die. I put the new plug in it and the thing runs like new. Sure wish I would of thought of that an hour before all the madness took place. Is this normal for a glow plug that is going bad? Is this something I can expect the next time I have one that is going bad?

ErikElvis

My Feedback: (2)

Yeah that sounds typical for a failing glow plug. A drop in rpm and difficulty running when pulling the ignitor is a pretty good sign.

opjose

A drop in RPM when pulling the ignitor can be due to many different things...

- Too rich of a needle setting
- Too much prime to the engine initially
- Too cold of a plug
- Too low percentage of Nitro content
- Fuel plumbing

etc.

Check your old plug. If you see a white-ish residue on the coil itself, this "debris" is what caused the problem causing the plug to need to be replaced.

Also try putting the plug on the ignitor and watch the coil.

The very last bit of wire will not glow because it is attached to the much cooler metal, but you'll find that on a new plug the last loop may glow, while on a old plug it may not. This also affects engine performance.

da Rock

Normal for a bad glowplug? Yes and no.

There are a couple of ways a glowplug can go bad. Some of those ways stop the plug from getting hot at all and won't let the engine start at all. But you've proven that plug was bad, and it would start the engine, so you've seen that kind of bad plug.

BTW, what you need to consider seriously, is why it went bad. A lot of times it because the element went soft from excess heat and being soft was pushed or mashed to the side. When the coils touch the side, they lose their heat just like has been explained already. Excess heat comes from too lean a mixture. Look closely at whether or not you're flying with too lean a needle setting. With our non-racing engines and our mild fuels, we really should never blow plugs. If you blow another soon, no matter if you think you're a magic man setting a needle, you probably are running that engine too lean. Or with a prop that really doesn't suit the engine/plane.

CGRetired

My Feedback: (1)

A glow plug has a coating of platinum that acts as a catalyst to the reaction between the heat (glow) and the fuel element. Often, the platinum coating wears away, or gets burned away caused by a hot mix, usually to lean a setting on the high-speed needle. And they can often just plain open up due to many causes... vibration, excessive heat, rough handling, just about anything. But, normally, if you keep the mixture set right, the plug will last a long time. However, they will go slowly, as yours probably did, and begin to show up as yours did.

That's why they are removable and easy to replace. Good ones are not relatively cheap, but neither is a gallon of gasoline now. I keep several OS3, OS8, and OSF plugs in my box, but they don't often get changed out. I think I changed one glow plug so far this year, and that's out of several glow powered planes. That's not a bad average at all.

Now, with that said, I seem to recall reading here on RCU about someone that changed the glow plug after each flight.. but he was flying pylon racing aircraft, with engines that generate very high RPM's.

CGr.

RCKen

My Feedback: (9)

To add to what CGRetired, Da Rock, and OPJose have said. Once an engine is broken in it's easy to have glow plugs last for literally years if you don't run lean and get them too hot. But when an engine is new it's common for plugs to go out. This is normal and is caused by the metal that gets worn away when an engine is breaking-in. So if the engine is still relatively new it's normal for the plug to go out.

Ken

Deadeye

It pays to run a tad rich. I have replaced only one glow plug in my entire RC airplane career (6 years). I average 4 cases of glow a year, with everything from 40 two strokes to 120 four strokes.