Airmicro

My Feedback: (2)

I'm lost here, and heres the funny part, i've been into r/c for 29 years and nitro for 18! Now I said that because I wanted everyone to kinda get a feel for my problem and why I'm stumped! This will be kinda winded to, so bear with me!

I have a revo with a O.S 18tm engine. It has maybe 1.5 gal's since break-in! It runs great! Wheelie's, no hesitation, no bogging etc. It temps about 220-230. It has started eating glow plugs about every tank. I have tried all different kinds too with the exact results! The truck will run great the whole tank, no overheating, great power the whole tank. I'll let it cool about 10 minutes and it won't start back up.

Take out the glow plug and it has a deformed coil in it! The coil will be pushed to the side, or the next coil down will be bent. Install another, run another tank, same thing. This has went on for 2 weeks now. I have adjusted my tune, but I think its about right. Nice trail of smoke through out the throttle, pinch the low-end, slightly rev's, then cuts out within about 3-4 seconds of pinching!

I have tried a little leaner, but truck doesn't perform right and runs a little hott at 260-270. Even if I do this, it still eats the glow plug! I have tried richen it also. It won't hardly shift because its too rich, so therefore, a Traxxas doesn't wanna shift if not tuned right. Even if I run the truck this way, eats the glow plug. Took the engine apart, and everything looks perfect!!

Ok, heres the interesting part! I have another 18tm setting in my showcase that I got from a friend who wanted more power, so I sold him my Picco .26 and took his 18tm in trade and cash! This engine has maybe a gal thru it! I installed it in my other revo thats basically brand new. I tuned it out, and it eats glow plugs like the other! I gave up after that, so I gave the 18tm to my friend who knows nitro decent, but no expert. He called last night and said you must have tried so much stuff trying to get this thing to stop eating glow plugs, that you had it too rich on the low-end.

He said he leaned it 2 complete turns, and it ran great in his revo, no glow plug problem. Ok, I took it tonight and installed it in my revo again tonight, and left it leaned out from what I had it, and it ran a little warm for me at 260, so I richened the hsn just a tad, and it temped about 236. It ran great as usual, and at the end of tank one, the glow plug looked pretty good. I let the truck cool 15 minutes, then ran tank 2. It ran great, wheelie's etc. temped about 230-240. At end of tank, I pulled the glow plug, and wa-la, glow plug coil shot!

Ok engine experts, whats up with all this? I thought I was close to being an expert for years, never having any nitro problems, and friends coming to me for tuning etc. but this has me humbled and stumped! Please if you don't have much nitro experience and just wanna say try this and that, please don't respond. If you truely know engines and think you know this probelm, then by all means, please help!

proptop

My Feedback: (8)

What fuel are you running? Sounds like maybe too much nitro...either that or put a shim in it.
When an engine eats plugs, generally it means it's over compressed, or too much nitro, or it's getting too lean/hot. (or a combination of those factors )

It sounds like you have it tuned o.k. so...about the only variable that might be different from your buddies set-up might be different fuel?

downunder

I'd take a guess it's fuel too and that maybe yours has some water contamination which could explain the difference in tune between what you had and what your friend found he needed. The fact that it's just started eating plugs, presumably on the same can of fuel, also leads me to think the fuel has gone bad. The only other reason an engine will develop an appetite for plugs is if there's some wear going on that's sending aluminium particles onto the plug coil. Aluminium is death to platinum but this doesn't deform the coil.

Airmicro

My Feedback: (2)

Thanks for the replies guys, but that won't be the answer. The fuel is only 20% sidewinder with 12% oil. I've used sidewinder for 3 years now and never a problem, plus when this started, I was on a half gallon that was 1.5 weeks old, and this week I was there when the fuel order came and got the 1st gallon out of the case! New gallon, new batch, same problem, plus my friend is using sidewinder and gets the same fuel at the same place, and usually within a day or two of when I buy mine!

Just can't for the life of me put my finger on this problem! I have went back over everything two or three times. Like I said also, truck runs like a raped banshee! Do you think maybe a little on the lean side causing it more than too rich?

bikeracer

Always worth while to check the rear bearing cage isn't breaking up when you suddenly start eating plugs.

.

j_blaze

how are you shutting down the motor, exhaust plug?

Airmicro

My Feedback: (2)

Just letting it run out on its own like I have for years! If I need to shut it down in the middle, usually squeeze the line.

Argess

With that kind of glowplug damage, it sounds way too lean to me. And I would say high speed is too lean. In other words, your HSN is too lean.

Why arn't the temps up? Why the smoke trail? Because your LSN is set too rich and it takes a while for the residual fuel in the crankcase to get burned off.....but it eventually does, and then your mixtrue becomes limited by the HSN setting, which is too lean.

Bring the vehicle in and measure temps? Well, by the time you get a reading, that rich LSN will have cooled it down again.

Another indication you may have too lean a HSN and a properly adjusted, or even too rich LSN setting, is that when you keep WOT for a little while, then let off, the engine idles high for a little bit and then drops.

Airmicro

My Feedback: (2)

I know for a fact that the HSN is perfect for the fact that as soon as you let off, the throttle immediately returns to idle, no taking its time to return. The engine is also supposed to be in the 2.5 turns out on the HSN, or there abouts, but mine is 3.5 turns!

We think we might have nailed the problem, maybe!! Today I messed with it some more, and it ate 2 more plugs, one after each tank! I thought I'd pull the engine again for the 20th time in 2 weeks, but this time permately, never to return back into this chassis, but I thought, why not get some new 20% Traxxas fuel, and try some of it. So far it has ran two tanks with my tune, and cross fingers, no eating of glow plugs!

I know for a fact after 18 years in Nitro I can tune an engine, and pretty darn well I might add, but this has been crazy! Now the reason I didn't rule out fuel before was because this started on my original gal. which was only 1.5 weeks old, and was supposed to be fresh when I bought it because they had just received their fuel 2 days before! Ok, last week I bought another Gal of same brand, plus they had just gotten it that day! That just seemed too far out there that 2 gal from 2 different fuel orders would do this, plus my friend is using the same brand from the same place, but no glow plug prob's!

In my past experience when glow fuel is bad, it usually won't tune, and the rc runs horrible! These 2 os engines have ran like rapped apes the whole time this has been happening!

Does anyone think maybe the manufacture got the nitro content mixed up when they made or, or maybe labeled it wrong? I don't believe its defective fuel, but maybe labeled wrong or something! I also know its not my handling of the fuel either, because I'm a perfectionist, believe me, ask my friends! I always keep my fuel in my truck and only get it out when I wanna fuel up my r/c, then back in the shade of my truck. My friends will set theirs right on the ground, and usually without puttting the cap back on. I'll tell them, hey that fuel is right in the sun baking, plus the pavement is hott, plus the cap is off, and they usually just laugh, and leave it!

Anyway, what the idea's here on the fuel being labeled wrong etc. Give all thoughts!

Thanks so far guys!

downunder

It's happened before where a manufacturer has made a mistake so it's possible. I don't recall the particular manufacturer but when they were told of problems they sent out a recall notice because they used batch numbers on their cans so it was easy to trace. If this is what's happened with your fuel, and reading back through your first post, then I'd say your fuel has far more nitro in it than it's supposed to have. That would explain both the distorted plug coil and the extra amount the needle was opened to get it tuned.

Airmicro

My Feedback: (2)

Just an update tonight from earlier. I went this evening with the new Traxxas fuel and ran with a friend to see if I could get more than a tank or two without crushing the coil in the plug as usual! I ran the first tank, plug looked new after! Ok, let it cool 10 minutes, fired up for tank 2. Ran great, temps down from 240-250 range like it has been running with the other fuel. Thought I would leave needles set where they were since it was running good, wheelie's, good topend etc.

I temped about half way thru 2nd tank and they were 210, which is what I usually run, but lately with this problem it runs about 250 to perform like it should. Ok, after 2nd tank, plug looked great! Really happy now because for the last few weeks I can't get more than 2 tanks without crushing coil. Let it cool, then fired up for tank 3. Temped about 210, ran perfect! Checked plug after run, looks great! Now I'm really happy!

Now tank 4! Fired it up, ran great, temped 212, great power etc. Checked plug after tank 4, and coil looked kinda like it was leaning over just a very little bit. Not distorted or smashed, but pushed over ever so slightly! Let it cool 10 minutes, and would it fire back up for tank 5! Yep, fired right up and ran great again! temped about 210, no problems!

Checked plug after tank 5, coil moved around inside plug. The coils aren't in a straight pattern down the plug, but pushed around some, but plug still lights, truck still starts! It was too dark for tank 6, soo.........

Well this is where I am now, so I'm kinda stumped! I will say that until now, 2 tanks and the show is over! The new fuel is letting me get more life out of the plug, plus I ran out of the actual correct plug that O.S recommends so I ran a #8 os plug, but I usually run those although its not the long reach, hott plug they call for. The os #8 is medium length, medium heat, but like I say, I usually run that plug and until all this started, I've never had a problem running that plug!

I guess this weekend I'll keep using the Traxxas fuel and try the longer, hotter plug they call for and see!

Any thoughts about this, please chime in!

chookman46

Have you stripped the engine and inspected thie internals yet. As mentioned earlier check the cage of the rear bearing and make sure that isn't falling apart. Also check the play on the big end of the conrod and make sure its not excessive. Clean everything, reseal it and try again.

This may not be the poblem as it is occuring with multiple engines so it is more than likely not a problem inside the engine but I would check just for peice of mind. Also check the tank and all the fuel lines in the car, see if there is anywhere that it could suck air from.

Also maybe try a different brand of plugs. I have had a bad batch of RB plugs before, you could only start them once. No matter how long they ran for 1/2 a tank or 4 tanks once you stopped them they would no longer glow to start. Bought a differnt batch and then had no problems. Try a colder plug to see if that makes any difference.

Airmicro

My Feedback: (2)

Yeah checked the engine inside and out, perfect! Thats the weird thing, (2) 18tm's, and (2) revo's! Both engines have been installed in both revo's! As far as plugs, its all been different ones. Carbon speeds, os #8's, os lc3's, mc59's etc. The only thing that has made one difference at all was yesterday when I went to another fuel and got 5 tanks before the coil started getting distorted, but still lights!

I am gonna try a colder plug and see what that does!

If the coils are getting moved around inside the plug, but not missing, would that be more like too rich, or too lean? The engine isn't giving any signs of either actually with it running so good and temping at 210 and the pinch test taking about 3-4 seconds, but who knows!

hrdcoreglf

What color are the coils? Are they shiny and grey, shiny and silver, dry and grey, coil color can tell you a lot. Does the top of your piston have pitting? My friend had the same problem with his OS .18 I think tz, and it turned out to be a bad carb and needed another head shim.

Airmicro

My Feedback: (2)

They are not as shiney as new, and kinda silverish! I kept a few from last weekend and they are bent up pretty bad. Coil all shoved up in plug!

I did another head shim yesterday and it ate a plug the worst it ever has! Wonder if the 3rd needle could be out of adjustment! Truck runs great, no hesitation, sputtering etc. and needle is in from flush just a little which is what O.S calls for, but....

dkastil

the deformed coil stumps me i was thinking you were running 30 % and getting detonation and you would have to shim but you run 20% if you are not running to lean like you stated ,there could be some fragments in your engine but you say it runs fine have you tryed a cooler plug and mabey a 1 mil shim or it can be as easy as just adding 1 more washer on your glow plug for a verry minute compression change ,also clean the engine better to be safe and after you clean you can seal

103/17

My opinion would be to check for whats changed in your exhaust system. If you are running a tuned pipe and header It sounds to me like your are charging the engine too hard with the pipe. In this case you get deformed elements or elements that are gone all together. We see this all the time in the piped planes when either the coupler sags and acts like a restriction or something in the pipe changes like a disc collapses or the outlet become obstructed in some way. I have also seen guys have an impact and the pipe slides forward then its shorter in length and tunes harder (more pulse into the engine) Can you back up the pipe a little? If it has a connector try making it a 1/4 inch longer. I bet if you remove the pipe as a test and just run a header you dont burn out plugs. This would be a good indication you might have a problem with the expansion chamber being too close or something changing in it. [:'(]

103/17