Go Back  R/C Tech Forums > General Forums > Rookie Zone
Keep destroying glow plugs. Why? >

Keep destroying glow plugs. Why?

Keep destroying glow plugs. Why?

Old 01-25-2011, 07:48 PM
  #1  
Tech Rookie
Thread Starter
 
Join Date: Jan 2010
Location: Yoakum, Texas
Posts: 11
Default Keep destroying glow plugs. Why?

I have a problem with the 24.7 engine in my XTM X Terminator 2 that that just baffles me. Last summer I lost the throttle servo and it stuck wide open. I ran it into a chain link fence and ran up to it as fast as I could then held a hardwood dowel against the flywheel to stop it. Not much damage was done and after a few minor repairs (and a new servo) it was ready to roll once again. Ever since then, it did not perform quite as well as it did before. Once it's warmed up if I nail the throttle wide open, I can hear the engine change pitch but theres a lull before it takes off. It sounds kind of like its bogging down. Before it used to just rocket off.

It still has that same symptom but now the glow plug lasts through only one tank of fuel then it wont light up. . Whats going on here? I thought the first time it did that it was just a fluke but I've tried two other brand new glow plugs and they both failed after one tank of fuel. I mean I can remove the glow plug after it's run out of fuel, place it in the starter, and it doesnt glow in the least. This car has only had a little over two gallons of fuel run through it. I monitor the temp while running it and try to keep it around 230 -245 deg.

Any ideas?

Thanks to all.
Dusty

Last edited by dusty trail; 01-25-2011 at 08:49 PM.
dusty trail is offline  
Old 01-26-2011, 07:42 AM
  #2  
Tech Master
iTrader: (15)
 
jbright33's Avatar
 
Join Date: Dec 2008
Location: shamokin pa
Posts: 1,352
Trader Rating: 15 (100%+)
Default

could be the rod has become ovalized. also if you run it out of fuel wide open it will kill the plug
Originally Posted by dusty trail
I have a problem with the 24.7 engine in my XTM X Terminator 2 that that just baffles me. Last summer I lost the throttle servo and it stuck wide open. I ran it into a chain link fence and ran up to it as fast as I could then held a hardwood dowel against the flywheel to stop it. Not much damage was done and after a few minor repairs (and a new servo) it was ready to roll once again. Ever since then, it did not perform quite as well as it did before. Once it's warmed up if I nail the throttle wide open, I can hear the engine change pitch but theres a lull before it takes off. It sounds kind of like its bogging down. Before it used to just rocket off.

It still has that same symptom but now the glow plug lasts through only one tank of fuel then it wont light up. . Whats going on here? I thought the first time it did that it was just a fluke but I've tried two other brand new glow plugs and they both failed after one tank of fuel. I mean I can remove the glow plug after it's run out of fuel, place it in the starter, and it doesnt glow in the least. This car has only had a little over two gallons of fuel run through it. I monitor the temp while running it and try to keep it around 230 -245 deg.

Any ideas?

Thanks to all.
Dusty
jbright33 is offline  
Old 01-26-2011, 07:13 PM
  #3  
Tech Rookie
Thread Starter
 
Join Date: Jan 2010
Location: Yoakum, Texas
Posts: 11
Default

How does the rod become "ovalized"? I never ran it out of fuel wide open. It ran, but not as well as it did before the throttle stuck wide open for a while when that servo went out. Its so strange. It will start (though not with just one or two pulls on the starter like it used to) and run ok as long as theres fuel in the tank. I can even re-fuel it on the fly without turning it off and keep running it with no problem. When I do shut it down, thats it. The glow plug is history. Crap. The only other clue is I can see through the hole where the glow pug screws into the head that the top of the piston is now black. It used to not be like that. Also, until this problem started, I was still using the original glow plug.

What should I do? replace all the moving parts in the engine? Replace the engine?

Please advise,
Dusty

Last edited by dusty trail; 01-26-2011 at 07:46 PM.
dusty trail is offline  
Old 01-27-2011, 06:14 AM
  #4  
Tech Lord
iTrader: (21)
 
Join Date: Jul 2008
Location: Houston, TX
Posts: 11,530
Trader Rating: 21 (100%+)
Default

Sometimes when nitro engines go wide open like in a runaway, the unrestricted rpm can cause the end of the rod where it rides the crankpin to elongate or oval.

It sounds like the glow plug coil is getting broken - as long as engine is running, a broken coil will stay hot and continue to run the engine. Once you shut it off, the gap in the coil prevents it from lighting again.

These are usually not worth rebuilding when the costs are considered against cost of new.
Duster_360 is offline  
Old 01-27-2011, 06:45 AM
  #5  
Tech Addict
iTrader: (9)
 
ALF420's Avatar
 
Join Date: Sep 2009
Location: Funkstown / Hagerstown MD.
Posts: 722
Trader Rating: 9 (85%+)
Default

Originally Posted by Duster_360
Sometimes when nitro engines go wide open like in a runaway, the unrestricted rpm can cause the end of the rod where it rides the crankpin to elongate or oval.

It sounds like the glow plug coil is getting broken - as long as engine is running, a broken coil will stay hot and continue to run the engine. Once you shut it off, the gap in the coil prevents it from lighting again.

These are usually not worth rebuilding when the costs are considered against cost of new.
+1
ALF420 is offline  
Old 01-27-2011, 02:05 PM
  #6  
Tech Adept
 
Pop35eye's Avatar
 
Join Date: Aug 2010
Location: Scottsdale, Az
Posts: 230
Default

Get a new motor.

The WOT probably burned out any pinch you had.
Is it possible the head is hitting the plug?
You can try adding a spacer or two to the plug
Pop35eye is offline  
Old 01-30-2011, 07:23 PM
  #7  
Tech Rookie
Thread Starter
 
Join Date: Jan 2010
Location: Yoakum, Texas
Posts: 11
Default

Today I decided to pull the head and have a look. With the shape of the combustion chamber the way it is, it would be impossible for the top of the piston to be hitting the plug unless that rod "ovalized" about an eigth of an inch or so. What I did find was what appears to be the after effect of the enging ingesting something, presumably metallic, hard enough to ding up the surface of the head and the piston in a few spots.


Upon close inspection, I could also see that the glow plugs were not working due to a break in the coils.

I assume whatever was bouncing around the combustion chamber was destroying the coil in the glow plug. I did remove one very fine granule of metal. The walls of the cylinder itself are still smooth as can be.

I dunno. I cleaned the burrs off the head and will try another glow plug to see what happens before I invest in another motor.

Has anyone seen this before?

Thanks to all,
Dusty

Sorry guys, I was going to post a picture of this but apparently I havent posted enough here to earn the privlege to do so. Just imagine the cylinder head with a couple of nicks in it.
dusty trail is offline  
Old 01-31-2011, 02:04 PM
  #8  
Tech Regular
iTrader: (16)
 
sm1nts2escape's Avatar
 
Join Date: Jul 2006
Location: MD
Posts: 444
Trader Rating: 16 (100%+)
Default

Was the piece of metal you found the glow plug coil? If your compression is too high. Say from a stretched rod,Say from over reving it. It will put little dimples all over the top of the piston (Like the texture of a golfball). That will cause a glow plug to not last long. And the broken glow plug coil will scratch the hell out of a piston and sleeve. Thats my guess to what happend. If you put a new plug in it and it's still hard to turn over by hand then I would try a new conrod. If you decide on a new conrod then flush the motor out with alcohol before putting it back together. I would prolly just buy a new motor though.
sm1nts2escape is offline  
Old 01-31-2011, 02:24 PM
  #9  
Tech Lord
iTrader: (21)
 
Join Date: Jul 2008
Location: Houston, TX
Posts: 11,530
Trader Rating: 21 (100%+)
Default

The are 2 common reasons glow plug coils break - overly lean running conditions and debris inside the motor. Your WOT episode turned something loose inside and it might not be just a single piece. High RPM can generate metallic particles coming off the bearings when they hit very high rpm.

Time will tell if what you removed will be the end of the prob on not. It's usually not....


You need 10 posts for linking pics....you can post one as an attachment though.
Duster_360 is offline  
Old 02-01-2011, 10:01 AM
  #10  
Tech Addict
iTrader: (11)
 
Dadic 78's Avatar
 
Join Date: Nov 2010
Location: Edmonton, AB
Posts: 732
Trader Rating: 11 (100%+)
Default

Just a thought, but it might be a piece of your conrod bushing that broke off in there, and is wreaking havoc. Had that happen to me once, same syptoms as you're describing. Going through plugs like mad! Very frustrating.

I just replaced the engine, and kept the old engine for parts. Saved the headaches.
Dadic 78 is offline  
Old 02-07-2011, 05:22 PM
  #11  
Tech Rookie
 
chase03's Avatar
 
Join Date: Jan 2010
Posts: 8
Default engine

i had the same thing happen to a hyper .21 but it had ingested something also but it put dings all in the top of the piston. i never over reved it or nothing it just happened never really knew what happened. it ran ok but started gettin rough idle then was hard as heck to tune . so i just replaced it.
chase03 is offline  
Old 04-02-2011, 08:48 AM
  #12  
Tech Adept
iTrader: (4)
 
Join Date: Dec 2009
Posts: 111
Trader Rating: 4 (100%+)
Default

you probably dont have the engine tuned properly
revo3 is offline  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.