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Overheating coil?
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local2Ed
Posted 2018-09-24 8:36 PM (#570723)
Subject: Overheating coil?


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1958 Dodge Coronet, 6cyl., automatic.

I was having a intermittent no-start problem that I believe I traced to the coil. It was an AutoLite coil that may or may not been original but it was the old style.
One of the other problems I was having was when warn, there was an irregular miss at idle That I could see in the engine movement and hear in the exhaust.
The car does not have a ballast resistor on the coil I replaced and don't believe one is called for.
Anyway, I put a new Intermotor, part # E40 ( supposed to be a BWD) coil that says "external resistor not needed"

The car starts fine and when I took it for a drive the miss at idle seemed to be gone. I drove it for a while and got home and left it idling in the driveway, the miss had returned and the coil was very hot to the touch just like the coil I had replaced. The coil is mounted on the side of the cylinder head on the 6 cyl. so I don't know if the coil is overheating from heat transfer from the engine or from over-voltage.

I am measuring full battery voltage to the coil, 12v to 14v depending on rpm's.
I've had this car for 5~6 years and don't remember if the original coil always was hot but it was in the car when I bought it and it never gave me a problem before and when removed there was no markings about using an external resistor with it and one doesn't show up in the wiring diagrams.

Would putting a ballast resistor on the new coil help if it is over-voltage causing it to become hot?
With the new parts today being what they are I don't know if I should trust the "external resistor not needed" on the coil.
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56D500boy
Posted 2018-09-24 8:45 PM (#570724 - in reply to #570723)
Subject: RE: Overheating coil?



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Location: Lower Mainland BC
Not sure if these diagrams help or not but they do show that the 6 cylinder didn't call for a ballast resistor. That said, it sounds like your coil *IS* getting too much voltage.

1956 Dodge:



1957 Dodge (I don't have one for a 58):





(57Dodge6CylinderIgnitionWiringDiagram.jpg)



Attachments
----------------
Attachments 57Dodge6CylinderIgnitionWiringDiagram.jpg (114KB - 26 downloads)
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Shep
Posted 2018-09-24 8:56 PM (#570728 - in reply to #570723)
Subject: Re: Overheating coil?



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Location: Chestertown, NY ( near Lake George)
Ive never seen a 12 v point ignition without some sort of resistor to drop the coil input voltage to maybe 7v in the run position, this will save the points. Coils normally get fairly warm. Some resistors are in the wiring, inline or internally resisted in the coil. Don't think this is your root problem. You could find out what the primary resistance is listed as for that coil and check it with a ohmmeter.
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local2Ed
Posted 2018-09-25 12:31 PM (#570750 - in reply to #570723)
Subject: RE: Overheating coil?


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Coil is working properly, battery voltage in, about 5.9v out to distributor so it is stepping down the volts correctly.
The temperature of the coil was 180* while the head it is mounted to was running 200*

I forgot that with this carburetor that is on there I could not get the pedal to go as far as the carb linkage toward idle. I have my idle set to spec when you let off the gas peddle but if you're under the hood and you push the linkage toward idle it will idle lower than spec and stumble.

I know the original coil was giving me trouble because when stopped at a light it would stumble/miss and more recently sometimes die out.
That is no longer the case.

Thanks for the reply's.
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Powerflite
Posted 2018-09-25 6:17 PM (#570770 - in reply to #570723)
Subject: RE: Overheating coil?



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Yes, the original coil you had, should have been about 0.5 ohm primary resistance and would require an external ballast to work. I am amazed that it worked as long as it did though. When I ran an original coil on my V8 without an external ballast, it shut off the motor within 5-10 minutes of driving. Dead, nothing until it cooled down enough to work again. So you probably had a higher primary resistance version than that.

Your "no external ballast required" coil has some resistance built into it. Here's the rub. 4cyl motors require 3 ohms primary resistance, 8 cylinders require 1.5 ohms, and 6 cylinders require.....you guessed it, 2.2 ohms. So my guess is that you have a coil made for an 8 cylinder with no ballast, and it is working on your 6 cylinder, but is *marginal*. You could add an extra .5 to .7 ohm external resistor to it to make it work better, mount the coil on your fender or firewall to allow it to heat sink better, or get a coil made for a 6 cylinder motor with the proper external ballast. An E-core coil is not subject to heating issues like the canister type coil is, so a higher (1.5 ohm or more) primary resistance version that won't burn up your points is another option. A coil made for a 4 cylinder will work too, but won't provide as much power. In fact, it may be true that there isn't a 6 cylinder version with internal resistance available because the factory just adjusted the external ballast to make it work well. Aftermarket companies came up with these internal ballast coils, and they may not have expected to sell any to 6 cylinder motors with points. So I suspect that if you ask at the counter what you should use, they will likely sell you one made for a 4 cylinder motor with 3 ohms resistance.

I hope this helps.
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local2Ed
Posted 2018-09-26 8:22 AM (#570780 - in reply to #570723)
Subject: RE: Overheating coil?


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There are different numbers for 6cyl. coil and 8cyl. coil. I have the 6cyl. number. This application uses a internal resistor coil I suppose because there is full battery voltage from the original wire leading to the coil and about 1/2 that voltage going to the distributor when hot. I haven't checked the voltage to distributor when cold but I am interested to see what it is. I may do that this morning.

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Stroller
Posted 2018-10-20 12:16 PM (#572043 - in reply to #570723)
Subject: Re: Overheating coil?


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Just wondering if you still have the famous chrysler coil resistor in place? I converted the famous lean burn system in an '85 Lebaron and forgot the resitor. The engine ran fine at first then started not running fine untill I put one in.
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local2Ed
Posted 2018-11-09 5:39 PM (#573242 - in reply to #572043)
Subject: Re: Overheating coil?


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Stroller - 2018-10-20 12:16 PM

Just wondering if you still have the famous chrysler coil resistor in place? I converted the famous lean burn system in an '85 Lebaron and forgot the resitor. The engine ran fine at first then started not running fine untill I put one in.


On my vehicle no external resistor is called for, there is nothing in the wiring diagrams and there are no loose or unidentified wires anywhere. The car is an original rescue/survivor.

I just want to follow up on some things I discovered.
Apparently I had two problems:
I was definitely loosing spark so I replaced points,condenser and coil.
Went out of town about 160 miles from home for a car show weekend and car would start to run hot after getting off the expressway or running 55mph. on two lanes roads when coming to a stop light. The car cooled down moving but would creep up but not boil over at a prolonged stop. The car never did this before. If I stopped long enough the car would eventually die out.

The morning we were set to leave the motel the car would not start, had good spark but was hard to start but eventually did. Only other times it would not start I was not getting spark but this time I had spark so this was a new problem.
I nursed it home avoiding the expressway and parked it a few days feeling it was a fuel/carburetor problem.

Couple days later I take it, car starts right up like normal, and within two blocks I can barely keep it running at any speed.
I get home and pull off the carb and I first notice the mounting nuts are very loose, So I think that very well could be a problem. I cleaned the carb and found nothing obvious but at least that is ruled out.

When I pulled my glass bowl fuel filter off the carb I put a plastic container under it to catch the fuel. I then dumped the fuel from the filter into the same container, probably just a couple ounces worth. It was several days before I got back to putting it together and when I took the filter out of the plastic container, which was left uncovered, I noticed about an ounce of liquid in the container. Upon smelling it, it had a very faint smell of gas to it, it did not smell of straight gas at all.

I put everything back together but before I hooked up the gas line to the carb I pumped some fuel into a large glass pickle jar. I was surprised to see the gas and water separating right before my eyes in less than a minute. I filled another jar and had the same results. I surmised since the car was parked for a few days any water would be at the lowest point in the tank so not wanting to shake the tank I hooked up a electric fuel pump an pumped out the remaining 8 gallons in a couple of 5 gallon closed buckets.

I then put some fresh gas in there and 1 bottle of ISO-HEET, the red bottle and the car is running just as sweet as she always has.

So to get to my point/observation, I don't know if I got a bad load of gas somewhere or if the condensation built up over the last five years since I last had the tank out but I had a lot of water in it.

I never really bought into the gloom and doom of ethanol laced fuel attracting water but the water came from somewhere and I just thought I'd post what happened to me and suggest it might not be a bad Idea to toss a bottle of the ISO-HEAT (red bottle) in the gas tank once or twice a year.



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