Glow plug problems
 

I have a new os 46 max engine which is burning out or causing the glow plug to fail. Tried resetting the carb, but still the glow plug only lasts one or two flight. I have used the #59 mc coy plugs, the #8 os plugs, the A3 os plugs. Hope someone can help. Thanks

what type of fuel and what size prop? has this engine been broken in ok meaning rich?
I never had any problems with os8 they are usually a very good and recomend plug

Plugs
 

Do the plugs not light up at all after you remove them? Sound like metal is tight somewhere as per last post and throwing debris into the plug shorting it out. Check all screws and try adding a bit of castor oil to the fuel.

the fuel Xtra performance 15% sport SYN: 75% GAS:25% OIL content 20% and the prop size is 11 x 6

won't contribute to the problem but 15% is at least 5% too much (basically, a waste IMHO).

Burning a plug out like this seems that the engine is running too lean at top end.

To set up: on ground, get the rpms as high as you can before they slow down--basically too rich (slower rpms) moves to max rpms (around 11,600) then goes too lean (slows down again)-->all this happens while you are turning the needle in (clockwise) from a too rich to a too lean needle setting.

When you hit that "middle" spot, stop and richen it (counter clockwise) till the rpms drop off about 600 (ie, if it peaked at 11,600, richen it up so it slows down to around 11,000). That should be suffiecient cuz when its in the air, it will lean out to give you the 11,600 peak.

What might be happening is you've got it set for that peak on the ground and so when it unloads in the air, you're leaning out too much.

Ok I checked all the screws, all appear to be tight. Some of the glow plugs don't light up. The other glow plugs still light up, but the engine doesn't run the way it should. The engine will stall at half of the rpms and also when the glow starter is removed the rpms drop off. As soon as I replace the plug with a new one the engine runs great.

Remote engine troubleshooting .... difficult at the best of times.

Wether or not a plug lights up is one indication, the second is, is the coil shiny. If it looks dull, even though it "lights up", it's no good as it's lost the catalyst coating.

This is the behaviour of the above described "dull" plug

Sounds like the plug. If you're going through them quickly, I think you're running too lean. Heed the good information above and richen your high end slightly. Also, be aware that you can burn plugs by not allowing for sufficient cooling. What does the installation look like, is the engine cowled in? If yes, is there sufficient cooling?

HTH, Jim.

ps. I run the same engine in my mustang. I did burn a couple plugs this summer on those really hot days but generally a plug will last me a full season.

I have only heard of this before so am basically just asking if this could be possible and perhaps someone else could comment on the likelyhood of this happening or not, but could it be that there is too much compression on the cylinder head causing the plug to prematurely burn out? I have heard of some folks putting a shim under the head to eliviate this problem although its usually with four stroke engines. Just adding something else to think about!

Plug failure
 

Hi,

I have heard that if you are using 1.5 volts (standard drycell) on your glow plug (MiMh and NiCd are 1.25 volts), and leave the glow starter connected while tuning, or leave the glow starter connected on the plug for a long period of time after starting, you can have premature plug failures.

Another cause can be an engine that is not fully broken in or the lining of the cylinder starting to shed, this causes bits of metal get into the plug and this will also cause premature failures.

In both of the above cases, the engine starts, runs well, but when turned off, will not start again.

I don't know where I got the above from, but I hope they will help isolate the problem.

Fly4Fun,

Wayne Miller

Maybe the fuel is contaminated or the engine has an air leak?