I have a GP dazzler that i put a tt pro 46 on. I have about 15 flights on it now. Since new it has leaned out in the air. I set it with a tach on the ground 400 shy of peak and take it up for a 6-7 min flight and all is well. But when i land it and refuel the plane it will not restart. So i take out the glow plug (os #8) and it will not glow. I have used 3 glow plugs in 15 flights. I am using a 10-6 prop and wildcat 10% nitro 18% oil. I think that the fuel might be foaming causing it to lean out in the air. There are small bubbles in the carb line while running it on the ground. I have put some looser foam around the tank and changed all the tank plumbing. Should i put a sintered clunk on it. It says that sintered clunks should not be used as a fill line?? I dont want to run a 3rd line. The os a3 that i tryed when i ran out of #8's did not burn out after several flights.

Any suggestions?

Glow Plugs fail for a number of reasons;
- too much current (from a power panel),
- old age,
- factory defect (poor production run),
- external contamination.

If you are getting a flight out of them, you didn't cook them with the power panel.
Old age is out.
Bad batch - is possible (but unlikely) - try again...

Contamination, can be from the way that you handle them on installation, to the way that you transport them in your flight box to (worst case) metal fragments in the engine...[X(] [:@]

You can solve the first two contamination problems by being vigilant.
Metal fragments in a new engine - can be disasterous! [:'(]

I would start by flushing the engine out with fresh fuel and examining the piston head through the glow plug hole, you can look at the piston side from the exhaust port. If there is any scraping you will see some evidence.

Depending on what you see, ... either take the engine to a dealer for a second opinion or go flying! - (The flushing could have removed all of the debris.)

Good Luck!

G'day Mate,
My advise is use an 11x6 prop, & balance it properly, tune your motor rich enough so that when you raise the nose of the plane at full throttle, it increases revs slightly, then it is rich enough to fly, without cooking plugs, & overheating.
Forget tacho tuning, use your ears, conditions change, tach readings don't, sometimes you can run a motor leaner, other times you need it richer, depending on the weather conditions at the time.
Use an OS #8 plug, & see the difference, when tuned correctly.
Also you must have an air leak in your tank, or you would not get bubbles in your fuel line, this makes it even more important to get your tuning right.

Still may too lean. Gotta go by the sound in the air, not a tach.

Try the H9 performance plug instead of the OS 8. Also, go with a APC 10-6.

While there are mechanical reasons for the glow plug to fail, the most common is running the engine too lean. What's the plug look like at the end of a flight?

It would be good to get to the bottom of the bubbles you said you saw. In addition, the tuning method you use might be resulting in lean flights. Following is the way I prefer to tun my engines.

Tuning – High speed needle
The following method is designed for sport flying where one wants reliable engine performance (minimum deadsticks) and long engine life (part of which comes from avoiding lean runs).

I’ll start off with a reminder that all needle adjustments should be done from behind the engine and that the plane should be firmly anchored or held. Never attempt to adjust the needle while holding the plane in the air. A small engine blip or wind gust could result in fingers in the prop.

Begin by gradually leaning the engine until you find the peak RPM. Once you find this, turn it several clicks rich. Once you’ve found this slightly rich setting, with a firm two handed grip on the plane, point the nose straight up. While you are doing this, remember to keep the propeller arc out of anyone’s face. When you raise the plane’s nose, one of three things will happen to the engine RPMs.

If the engine speeds up slightly and holds that speed for 10 to 15 seconds, pat yourself on the back (after you put the plane down), you’ve got the needle set pretty well.

If the engine slows down, or does not speed up a bit, it’s too lean. Lower it immediately, turn it a few clicks richer and try again.

If the engine speeds up significantly, it could probably be a bit leaner. Put it back down, set it a bit richer and try again.

That’s it, no magic…

Good advice for a tuning technique.

Glowplugs burn out when the needle is too lean. It's also very touchy to set the needle properly when the chosen prop is too small for the engine. It was good advice to try a larger one. A 10-6 is an excellent prop for a .35, but is a bit on the small side for a .46. All my 46s run best with 11" or 12" props on them. And none eat glowplugs. What happens is the too small prop unloads way more than a proper sized one.

Actually, if you keep using the tach it will be a good and useful tool. It just takes some experience, enough to realize that a lot of advice isn't really good advice.

sounds way too lean to me... you should see exhaust while airborne

One other thing that I didn't see mentioned above. An engine with excessive wear can cause glow plugs to go bad too. Basically metal flakes in the oil will cause them to burn out. Examine the exhaust residue left on the plane after a run. If you see light grey or black in the residue there's a good chance you have metal wear going on.

Just something else to look for.

Ken

First, fix the air bubbles. You probably have a pin hole in a fuel line or some other air leak. The thing about bubbles is that they make the engine run lean. You can "tune them out" on the ground and the engine will seem to run ok even with the bubbles. But in the air things change, and the engine will lean out a more than normal. And a lean engine run can kill a plug.

I also agree that using a bigger prop might help you out a bit. While a 10x6 isn't going to hurt your engine, you will be running at a pretty high RPM, and with a new engine (you said 15 flights on the plane, that's for the engine too, right?), you'll usually have some prety high compression. If you want to run at that RPM, you might need a colder, heavy duty plug meant for high RPM operation. The OS #8 is a good general purpose sport plug, but there are better choices for high RPM running.

piper chuck's engine setting instructions are right on, but I want to add a couple of things.

First, all engines are a little differnet when it comes to the needle valve sensitivity. On some, backing off of peak rpm "2-3 clicks" is plenty. On some, you need more like a half-turn. On others, just 1 click is enough. It depends on the design of the carb, your fuel, the weather, and other factors. I have a TT .46, and it has a very broad needle range (a good thing) (at least the way I'm running it). So you might need more than a few clicks when backing off of peak rpm.

Second, if you can't pick the plane up to do a "lift test", you can also pinch the fuel line (if you can reach it). Give the fuel line a good hard pinch-and-release and listen. The pinch will block the fuel flow for a moment, causing the engine to lean out. You should hear the engine pick up RPM. If it sags or the RPM doesn't change, it's too lean already.

Remember that in the air, the engine will run at a higher RPM than on the ground. How much higher depends on the prop, airframe drag, and other factors. This increase in RPM will require more fuel. Since the mixture is set on the ground, the effect is that the engine runs leaner in the air than on the ground. Sometimes much leaner.

First, ya need an 11 inch prop. You also sound too lean still. The lean condition may also be doing the damage at idle. Nobody seems to be mentioning that because it's USUALLY the high speed that causes the problem but not always.

I go along with piper on the lean thing here. Check the routing of your lines. Any type of 90 degree bend can yield a pinched line. May not look enough to cause problems but will lean out in the air. Been through it

Wow a lot of good info guys. So far so good. The bubbles in the fuel line are just about gone. I dont get them until im almost out of fuel. But i set the engine rich on the ground by the pinch test and holding the plane vertical but it still seems to lean out in the air slightly. But today i did not burn up one plug with 4 flights. In the dazzler the 6oz fuel tank is pretty tight to all the sides. But enough space for some small foam on all sides. I think im getting a small amount of foaming. I may try a sintered fuel pick up. The golw plug looks like new when i take it out after the flights today, but the ones that quit glowing also look good to the eye, not melted or deformed?

Thanks again guys.

Hi!
Install a second clunk in the tank ...called Uniflow set up ...where you connect pressure from the silencer...if this doesn't help ...get aTettra "bubble less" tank.

Perhaps I am missing something here. So your plug burns out after you land and taxi back to the pits and you cut off the engine? Is this correct? As soon as this is done, pull the plug and see it is burned out. What are you using to ignite your glow plug on the re-start?Sometimes new engines will burn out plugs until broken in. If the A3 is working for you stay with it and fly.

A plug can "burn out" (break the coil) right after you've started the engine but you'd never know until the next time you tried to start it. A broken coil means no electrical circuit but once the engine is running it doesn't care about electrical continuity, so long as the coil is still there it'll keep right on glowing all through a flight. Back in the *ahem* earlier days we used to take a pin with us so if the coil broke we could dig around inside and get the broken ends back into contact for the next flight .