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Glowing Spark Plug

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RunningW View Drop Down
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    Posted: 03 Dec. 2017 at 7:21pm
Has anyone ever melted down a spark plug?  Somehow I managed to cook a spark plug and plug wire on #4 cylinder.

So there I was, stalled out on TX 73 in the dark of night.  I had just finished running Crystal Beach along the gulf coast to Port Arthur.  For anyone considering it, I'll tell you, you can't make it at high tide.  Everything was running smooth until I got to Winnie, TX and Lil' Red started sputtering intermittently.  I knew I had fuel and the volt meter didnt give any indication of main power issues. 

I pulled into a nice brightly lit truck stop and inspected everything.  Everything appeared tight and it idled just fine.  Five miles out of town, she started sputtering and died on me.  I popped the hood and was startled to find the base of the #4 spark plug glowing a dull red in the dark of the highway and the plug wire and rubber boot melted away.  I replaced the fried AC Delco with a spare Auto-lite, clipped and soldered the plug wire back together, and I was back on the road without further incident.  Looking at the base of the plug in the light it appears to be melted.  I just put the new plugs in three weeks ago and gapped them at .020" instead of my usual .030".  I'm not sure that had something to do with it, but the other three were fine.

Fast forward a few days and the sputtering returned along with reluctant starts.  After rechecking everything and regapping the plugs to .030", I finally dropped in a spare igniton coil I had with me and she's back to running like a dream.  I don't know what happened, but my spare parts supply took a hit these last couple weeks.  Any ideas?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote wadoyado Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec. 2017 at 8:04pm
From my experiences, first thing comes to mind to get it that hot is a leaking (usually) exhaust gasket, or manifold. something allowing out side air into the combustion area, even loose sparkplugs could do it. The coil things got me a little baffled. It could also be no. 4 is way out of time, but usually not just one cyl. Just suggestions Joe I know the feeling of looking under the hood at night and seeing glowing red engine parts.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec. 2017 at 8:05pm
 Off the top of my head, it sounds like the coil was being over powered. Were you running a 6 Volt coil on 12 Volts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RunningW Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec. 2017 at 8:44pm
Everything, including the coil, is 12v. Power output from the alternator looks normal.  Every time I think I got this vehicle figured out she throws me a curve.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec. 2017 at 8:48pm
A lean mixture can burn VERY hot. Melt pistons, etc. Is your windshield wiper hose attached?  BW
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shadow Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec. 2017 at 11:25pm
I think Bruce is on to something there, with the vacuum wiper hose or port open the # 4 cylinder could be running very lean causing the melt down , be carful you don't want to burn a valve or piston
lets go for a rip eh bud

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stev Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec. 2017 at 8:38am
I like Wayodado's idea of air getting in around the plug.  Spark plugs usually come with a crush washer to seal the plug.  If oxygen is getting in from around the plug it is going to burn what oxygen same as with a bad exhaust gasket leading to a burned valve.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RICKG Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec. 2017 at 12:52pm
Originally posted by Stev Stev wrote:

Spark plugs usually come with a crush washer to seal the plug.   
 
Got a source for the crush washers only? After checking the plugs for condition 2-3 times the washer is no longer effective..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 12:39am
With the engine running, I am not sure how oxygen is getting into the cylinder past the spark plug. Since the cylinder is almost always at a higher pressure than the outside air, a bad spark plug gasket will leak the compression out into the outside air.

Like Bruce, I am more likely to expect to find a vacuum leak in the wiper system, causing a lean mixture. Since the port for the wipers is closest to #4 cylinder, it would be the one to get the hottest. IIRC, #4 runs the hottest anyway. So yes, check the hoses, etc, for a vacuum leak in the wiper system.

I am concerned about possible damage to #4 cylinder, its piston, & its rings. When a spark plug glows red, that is very hot! Are the rings annealed? Is there a hole blown through the top of the piston? Is the cylinder cracked? Maybe the valves are warped. Do a compression test to see how #4 compares to the other three. Please & Thanks.

Another concern is the coil failing just after the spark plug failed. I never liked that kind of coincidence.  My thoughts always go to: Is it coincidence, or cause & effect? Hence my first reply. 

I will wait for the results of the compression test.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wadoyado Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 9:32am
When the piston moves down to draw in the fuel air mixture, if the plug is not sealed it will draw in outside air. Right? A leak in the system can cause it to run lean. IMHO
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpet Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 10:27am
This may not be the same thing, but one time, my timing was off enough that my exhaust manifold started glowing dull red right at the head and burned up a plug wire. I didn't notice it till it was dark out and I popped the hood. Just a thought and easy to check.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeeper50 Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 11:10am
Originally posted by jpet jpet wrote:

This may not be the same thing, but one time, my timing was off enough that my exhaust manifold started glowing dull red right at the head and burned up a plug wire. I didn't notice it till it was dark out and I popped the hood. Just a thought and easy to check.
 
Hmmm had the same thing happen to me last year with my 3B, but didn't realize it had happened until weeks later. Bought another plug wire and drove on. All good now
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 1:17pm
Originally posted by wadoyado wadoyado wrote:

When the piston moves down to draw in the fuel air mixture, if the plug is not sealed it will draw in outside air. Right? A leak in the system can cause it to run lean. IMHO


Perhaps, but IMHO, It will pull the spark plug down with the first rush of air & this will seal off the leak. Remember that the exhaust stroke just happened & air is at that time moving out of the cylinder. The exhaust air has to stop & reverse direction before any air can be pulled in. When & if any air is pulled in the air will mostly be exhaust gases, not oxygen. Due to these factors, I doubt that enough oxygen will come in in that short time to effect the mixture enough to cause the overheating problem.

IME, (In MY Experience), Admittedly on air cooled engines, when a plug is loose, the engine will lose power. Holding my hand over a loose park plug I feel pulses of air moving out of the cylinder. The symptoms that led me to go looking for a problem was lack of power & low MPG. Never was it an overheating issue. As I am sure you know, air cooled engines are very susceptible to overheating. Thus, IME, loose spark plugs do not cause overheating issues.

I am not trying to be an ass. I am trying to find the overheating issue. If any other mechanics out there have ever had a serious overheating issue caused by a loose spark plug, I would like to hear about it.

Heck, lets ask the OP if that plug was finger tight when he changed it. If it was not, then a loose plug was not his issue.   

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 1:59pm
Originally posted by wadoyado wadoyado wrote:

When the piston moves down to draw in the fuel air mixture, if the plug is not sealed it will draw in outside air. Right? A leak in the system can cause it to run lean. IMHO

You may be right, but at that point, the inlet valve is open, and a lot of air/fuel mix is rushing in to fill the void. The air that could enter past the loose plug gasket and threads would be very small.
  One thing, tho - the spark plug is cooled by its contact with the cylinder head. Heat is drawn off through the gasket/mating surface and the threads. If the plug was loose, it would certainly overheat. To this extent? I don't know. I have seen plugs that were loose that also had the electrodes burned off. 
 " Heck, lets ask the OP if that plug was finger tight when he changed it. If it was not, then a loose plug was not his issue."  I was thinking the same thing.   BW


Edited by Bruce W - 05 Dec. 2017 at 2:03pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wadoyado Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 3:07pm
Originally posted by Bruce W Bruce W wrote:



You may be right, Heck  </span>BW

      Thanks Bruce One thing about you Colo. guys you sure get the rusted gears in this old noggin moving again!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec. 2017 at 9:34pm
Originally posted by wadoyado wadoyado wrote:

Originally posted by Bruce W Bruce W wrote:



You may be right, Heck  </span>BW

      Thanks Bruce One thing about you Colo. guys you sure get the rusted gears in this old noggin moving again!

Didn't mean to gang up on ya, it just happened that way.Wink I'm sure the roles have been reversed at one time or another. I don't know all, nobody does, and I try not to come off like I think I do, unlike some we've heard from from time to time. I just like to try to get them ol' rusty gears a-movin', mine and yours alike.Smile  BW
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 06 Dec. 2017 at 1:55am

Originally posted by Bruce W Bruce W wrote:

Originally posted by wadoyado wadoyado wrote:

Originally posted by Bruce W Bruce W wrote:



You may be right, Heck  </span>BW

      Thanks Bruce One thing about you Colo. guys you sure get the rusted gears in this old noggin moving again!

Didn't mean to gang up on ya, it just happened that way.Wink I'm sure the roles have been reversed at one time or another. I don't know all, nobody does, and I try not to come off like I think I do, unlike some we've heard from from time to time. I just like to try to get them ol' rusty gears a-movin', mine and yours alike.Smile  BW


Me three! Smile Especially the "I don't know all" part. As long as our rusty gears are moving, then we have a chance to keep our rigs moving. Big smile Cpt Logger, AKA Matt W.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote athawk11 Quote  Post ReplyReply Direct Link To This Post Posted: 06 Dec. 2017 at 11:27am
Someone here...or somewhere, described an engine as a big 'ole air pump.  I don't know why, but this helped me develop a better understanding what is happening in an internal combustion engine.
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