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Author Topic: ingnicion coil overheating  (Read 9519 times)
 
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davidk
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« on: November 06, 2010, 02:56:24 PM »
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Help! I recently bought a beautifully restored 66 Bug.  There is only one problem.  After 30 minutes of so of driving, the engine starts to stumble.  I discovered that the coil is way too hot.  I have been to four electrical mechanics here (I live in Mexico, a few kilometer north of Puerto Vallarta).  None can find the problem.  I have installed four different coils.  Same problem. The original 6 volt system has been replaced and a 12 volt system and a 1500 cc engine installed.  I don't think it is the coil.  Something else is making it hot.  Gracias for any suggestions.

David King
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« on: November 06, 2010, 02:56:24 PM »

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Rick G
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« Reply #1 on: November 06, 2010, 06:04:50 PM »
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My coil gets hot too. Check your coil, instructions here

http://www.vw-resource.com/tune-up.html#coil

If it looks good, go with it.
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« Reply #2 on: November 06, 2010, 08:06:10 PM »
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All coils get hot... 30k plus voltage will do that.   Grin
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buggyman
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« Reply #3 on: November 06, 2010, 10:23:30 PM »
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 Grin
Dayo dk Smiley ,
"I have installed four different coils.  Same problem"
Then the coil isn't the problem Wink .
"After 30 minutes or so of driving, the engine starts to stumble....The original 6 volt system has been replaced and a 12 volt system"
What condition are all your wires & wire connectors in?
If it was converted to 12v using ~44yr old wires they themselves may be compromised as in too high a resistance value which creates heat Wink .
If the actual wire connectors(terminals) are too loose that increases resistance which also creates heat,this can happen on both the +power side & -ground side,so ya gotta double check that all spade connectors are actually a little difficult to initially install & not easy to move & that all ground paths are rock solid Wink .
 Grin
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davidk
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« Reply #4 on: November 07, 2010, 08:39:22 AM »
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Thanks for the comments on vapor lock and old wiring.  I'll retune the carb today.  The Bug doesn't start as easily as it should but the plugs are a good color so nothing can be seriously out of sinc.  Regarding wiring, one mechanic told me that I should renew the ignicion-to-coil wire.  Two others told me that is had already been renewed.  Is there a particular wire or wires that I can check other than those easily visible in the engine compartment?

David
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« Reply #5 on: November 07, 2010, 05:49:41 PM »
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Thanks for the comments on vapor lock and old wiring.  I'll retune the carb today.  The Bug doesn't start as easily as it should but the plugs are a good color so nothing can be seriously out of sinc.  Regarding wiring, one mechanic told me that I should renew the ignicion-to-coil wire.  Two others told me that is had already been renewed.  Is there a particular wire or wires that I can check other than those easily visible in the engine compartment?

David
Not sure what is wrong with your car, but don't just focus on electrics... could be carb, timing, etc.  Check all areas... I have learned this the hard way.  Banghead
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« Reply #6 on: November 08, 2010, 08:12:53 AM »
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Thanks for all comments.  I've got new points, condenser, a new fuel pump and I'm familiar with the carb tuning process.  The mechanics here have checked the timing.  Bugs are common down here ane there are a lot of good mechanics who know them well.  So far, after checking everything else, the just put in new coils. It runs great until the stumbling starts. I want this car to run as good as it looks.  David
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« Reply #6 on: November 08, 2010, 08:12:53 AM »

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davidk
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« Reply #7 on: November 12, 2010, 12:33:56 PM »
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I had an electronic ignicion system installed.  No more rough running.  The Bug runs great.  But the coil is still too hot to hold after the 10 minutes of driving.  This bothers me.  People I've talked to here tell me that the coil should be warm but not hot.  Does anyone have experience with this? 
David
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« Reply #8 on: November 14, 2010, 02:43:06 PM »
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 Grin
I had an electronic ignition system installed.  No more rough running.  The Bug runs great.

 headbang

But the coil is still too hot to hold after the 10 minutes of driving,this bothers me,does anyone have experience with this?

dk Smiley ,exactly Wink where & how is your coil mounted?:
1)In the stock position?
like

2)In an alternate spot?
like

3)Wrapped with a cover(like an empty Beer can Roll Eyes ) or facing up?
like


1)The stock position is best with all engine compartment seals installed,that ensures that only fresh,unrecirculated air passes by the coil Wink .
2)Depends on where you put it Wink .
3)Wrapping it with a cover just retains heat or installing it upside down exposes the terminals to an air gap in the oil inside it which is supposed to collect & dissipate that generated heat Wink .
Something about your overall setup is either generating or retaining heat within the electrical system because IIRC I had mine running on the very same Bosch blue coil I acquired in the early 1980's Shocked ,so the actual coil itself should not be the real problem.
Click & post up some pics of your setup,lessee what we can see Wink .
 Grin
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« Reply #9 on: November 15, 2010, 10:43:43 AM »
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My coil gets too hot to touch after about 1/2 hour.  with no problems - High ambient temprature going on under the lid.  I had a computronix coil go out after about a year and a half, funny thing was the primary side would go open when it was cold and no spark, once the outside temp. warmed up, she fired right up and ran great as long as the coil was warm to hot.
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davidk
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« Reply #10 on: November 15, 2010, 02:49:04 PM »
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To reply #8.  I'm not that familiar with posting photos, but my car has the coil in the exact postion of your photo #1.  The only difference in the engine setup is I have an oil bath airfilter. I don't know what you mean about "engine seals."  My 66 doesn't have anything that I would call a seal.  To reply #9.  I know an American guy down here who had a Bug garage in the U.S.  He says the coil should be warm, but not too hot to hold.  A couple of Mexican mechanics said the same thing.  Mine is too hot to hold after 15 minutes. The car runs great, but I'm concerned that the coil will just fry itself some day.  Winter days down here are 85º Farenheit.  Summers are 95º, so there is no assistance from outside air temperature. The engine temp, fully warmed up, is a little less than 200º according to my wife's cooking thermometer which has a probe that goes to the bottom of the oil sump, so engine overheating is not an issue. Thanks for your answers.  David
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VolksDragen
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« Reply #11 on: November 15, 2010, 03:43:49 PM »
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David,
Your coil mounted same as photo #1 - thats good, it's VW original installation. Smiley
"Engine seals" as Buggyman refering to is the rubber that seals between the engine tin and the body, If those seals are shot, HOT air from the exhaust and heated air from the engine is drawn upwards into the engine comparment and EVERYTHING will be too hot to touch.
Hope all of our 2-cents helps  Cool
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davidk
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« Reply #12 on: November 15, 2010, 05:43:13 PM »
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I'll check tomorrow, but please help me out by identifying exactly where the, "engine tin," is. The only seal I found was a rubber weatherstripping type strip that rims the body where the "hood" meets the body when the hood is closed. The motor and it's components do not seem hot. This car has been carefully restored and everything is perfect except for the hot, hot, coil. I grew up with Brithsh sports cars but this is my first Bug. It is a lot different. David
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buggyman
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« Reply #13 on: November 15, 2010, 10:46:27 PM »
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 Grin
Dayo dk Smiley ,
"The only seal I found was a rubber weatherstripping type strip that rims the body where the "hood" meets the body when the hood is closed."
That'd be the decklid seal,#46 here:

"but please help me out by identifying exactly where the, "engine tin," is."
#'s 1,23,& 30 here:

Those are the primary pieces of engine-bound metal shroud which contact the 2 main engine compartment seals,#20 which runs across the firewall(#5),& #19 which actually is attached to both the rear apron(#17) & 1/4 panel shelves(#14) shown here:

If those aren't there in an enclosed engine compartment then you are recirculating at least some of that almost 200º engine generated heat right back through the cooling fan.

"Winter days down here are 85º Farenheit.  Summers are 95º, so there is no assistance from outside air temperature." Huh
95º & 85º are over 100º less than your measured oil temp,I ran easily all day every weekend for ~20yrs in ambient temps ranging from a little below freezing to ~115-120ºF,so given that you're running within a reasonable engine temp range & only the coil seems Wink to be an issue,it's either the quality of the coils or an isolated electrical resistance problem in the wiring associated with it which is repeatedly making them fail so often.
 Grin
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« Reply #14 on: November 16, 2010, 07:00:08 AM »
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Thanks for the diagrams and comments.  I'll check the engine seals today, but the restoration on this car is so good that I expect to find them properly installed.  I'm thinking that there is an electrical problem associated with some of the wiring being original from 1966.  I've bought this up with the mechanics who have worked on the car, but no one has been able to identify a wiring problem. Thanks again. David
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davidk
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« Reply #15 on: December 07, 2010, 02:38:55 PM »
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Karma and/or Buggyman.  If you're still out there, a little more direction please. I read your posts about the importance of seals around the engne tin to keep hot air out of the engine compartment. I also read on Rob and Dave's website on cooling and engine tin that "air management" is very important in Bug cooling. My engine seems to be missing the seal between the tin numbered #1 on your latest post, and the fan shroud.  In fact, if I shine a flashlight in back of the oil fill cap and down, I can see a gap of at least 1/2".  I can see the cooling vanes of one of the right hand cylinders. Question.  How can I fill this gap?  None of the auto parts stores here seem to know anything about it.  One mechanic told me I would have to have the engine dropped.  Is there any kind of material I can stuff in the gap that would seal off most or all or the air coming into the engine compartment? Thanks for continuing on with this.  Davidk
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« Reply #16 on: December 08, 2010, 05:28:54 AM »
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I have a similliar problem and did find a problem I have yet to attend to.  The coil says none internal resistor, I have compufire in dist. and it requires a coil with an internal resistor OR I believe I can put in a ballast resistor with starting done with full 12 volts. ED I believe that will cause a hot coil. ED
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buggyman
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« Reply #17 on: December 08, 2010, 11:03:26 PM »
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 Grin
Dayo dk Smiley ,

"Karma and/or Buggyman.  If you're still out there, a little more direction please."
I don't know who Karma is Dontknow ,so I'll answer it Wink Tongue Cheesy .

"My engine seems to be missing the seal between the tin numbered #1 on your latest post, and the fan shroud.  In fact, if I shine a flashlight in back of the oil fill cap and down, I can see a gap of at least 1/2".  I can see the cooling vanes of one of the right hand cylinders. Question.  How can I fill this gap?"
Sounds like you're talking about a 1/2" Huh Shocked gap between #1(cylinder shrouds) in this? pic

& the fan housing,#1 in this? pic

If so,there's no way "the auto parts stores here" could know anything about it because there is no seal intended to go there because that's intended to be a tight interference fit between the upper & lower pieces where the upper edges of the lower pieces bow in toward each other(/ \) & the lower edges of the upper piece bow away from each other(/ \) to create a situation that looks like this:
[Front of cylinder shroud // fan shroud \\ back of cylinder shroud as seen in profile from either side of the car]
so they lap together tightly metal to metal.

Odds are pretty good since there's suchShocked a large gap in that one spot that your gen/alt belt is not set perfectly verticle(gen/alt pulley set farther toward the front of the car than the crankshaft pulley below it is) as seen in profile from either side of the car so:
"One mechanic told me I would have to have the engine dropped."
would probably be the best/easiest way to to be able to pull the fanshroud off & spread apart it's lower edges & pinch in the upper edges of the cylinder shrouds toward each other cleanly for a tight final fit between them using a wide-jawed vicegrip in order to maintain consistant smooth surfaces,that shoud correct any misalignment between the pulleys & increase belt life.
If there is no misalignment of the pulleys now then it should just be a matter of just loosening all the screws that hold tins #'s1-23-30-&33 in pic 12 above together,raising the fanshroud up after removing the end screws(#3 in pic 10),pinching the inboard engine block ends of the #1's together so it makes it hard to set the fanshroud back into place & then retighten all the other screws that were loosened.This can be done with the engine still installed but it's way easier with the engine out,the difference of a 2-3 man job as opposed to a 1 man job Wink .
 Beer Grin
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« Reply #18 on: December 09, 2010, 01:23:36 PM »
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Thanks Buggyman.  I will take my Bug to a shop and have this corrected.  I'm too old to mess with this myself.  Besides, mechanical work is very inexpensive here in Mexico and if you know where to go (I do) it is also very high quality work.  I don't know if this will affect my coil problem, but the engine compartment is too hot after a long drive and eveything in it is hot too. Davidk
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davidk
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« Reply #19 on: January 17, 2011, 07:19:35 AM »
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I appreciate all the information I've gotten on this forum.  I've followed all the advice.  But the problem remains - an overheated coil.  I had an electronic ignicion system installed and the Bug runs great - but the coil is still too hot to touch.  The coil put in by the shop that installed the ignicion system is, "sin resistencía," (without resistance).  Would it be okay to try a coil "with resistance?"  I read on an Internet website that resistance will lower coil temp.  I'd like to try it, but I don't want to experiment around and mess something up more than it is now.  davidk
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« Reply #20 on: January 17, 2011, 08:55:32 AM »
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I appreciate all the information I've gotten on this forum.  I've followed all the advice.  But the problem remains - an overheated coil.  I had an electronic ignicion system installed and the Bug runs great - but the coil is still too hot to touch.  The coil put in by the shop that installed the ignicion system is, "sin resistencía," (without resistance).  Would it be okay to try a coil "with resistance?"  I read on an Internet website that resistance will lower coil temp.  I'd like to try it, but I don't want to experiment around and mess something up more than it is now.  davidk

my compufire requires a resister coil or it will run hot. you many want to check with the people who make the module, mine calls for a resister coil in the parts book ED
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« Reply #21 on: January 17, 2011, 01:21:30 PM »
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Er. I was under the impression you needed a resistor coil as well...
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« Reply #22 on: January 22, 2011, 12:22:53 AM »
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The electrical circuit for the coil and points should have a 3-4ohm resistance to reduce the current.  Too much current through this circuit will cause:
  • hot coil
  • burnt point contacts
  • burnt out electronic ignition module

Most round canister coils seem to be either low resistance (<1ohm) or "with resistance" (1.5ohm and up).
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davidk
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« Reply #23 on: January 22, 2011, 07:58:03 AM »
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Ashman40, thanks for your reply. Before reading it, I bought an extra coil yesterday, thinking that if the other one blew up, I would replace it, on the road if necesssary.  The new one registers 2.0 ohms across the positive and negative terminals.  I'm assuming that the one in the car is the same.  The one I bought yesterday is #SP5-10WC. The mechanic who installed the electronic ignicion system told me that I needed a "without resistance" coil for this type of ignicion system. Your description of the problems associated with a coil with low resistance are consistant with what I have encountered. Where do I go from here?  Do I need another type of coil?  Bugs are common down here in Mexico and parts are easily available.  Davidk
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« Reply #24 on: January 22, 2011, 08:20:33 AM »
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Ashman40.  I measured the coil in the car, it is 1.5 ohms.  My Bug looks and runs great.  I thought that carring a spare coil would be good insurance against a coil failure but now I'm afraid to drive it for fear of burning out the ignicion system. Davidk
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