No good coil
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- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: No good coil
How about measuring the resistance of the primary and secondary coils? The primary coils contact to the posts with nuts and should not have a lot of resistance. The secondary would be where the wire to the distributor plugs in and where the coil is grounded. This circuit should have a lot of resistance but not be open.
Lowell Brown
1966 Gold 330 2+2 Series II
1966 Gold 330 2+2 Series II
Re: No good coil
John: in most coil failures, the car will intially run fine. However as heat develops in the coil, the engine will lose power until it dies by the side of the road. After a "cool off" period, the engine will start and run well again, then the cycle will repeat itself.
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- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: No good coil
Hi Dyke, that sounds like what I am experiencing. The car runs, but when I step on the throttle the power isn't there. The other thing is that when I compare resistance readings between the coils the readings are different.
Has anyone tried fitting a modern coil inside the original can? I am asking about this not because I'm cheap, but because I like the faded look of the Bakelite and want to keep it.
john
Has anyone tried fitting a modern coil inside the original can? I am asking about this not because I'm cheap, but because I like the faded look of the Bakelite and want to keep it.
john
PF Coupe
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- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: No good coil
Hi Dyke, how would the engine run if one of the distributor resistors was bad?
I am going thru things and noticed that with the ignition key on only one of the resistors gets hot. The other is quite cold. So, looking at your average ignition diagram on the internet, the resistor and the primary winding of the coil are in series, so if the resistor does get juice thru it neither does the primary coil, right?
john
I am going thru things and noticed that with the ignition key on only one of the resistors gets hot. The other is quite cold. So, looking at your average ignition diagram on the internet, the resistor and the primary winding of the coil are in series, so if the resistor does get juice thru it neither does the primary coil, right?
john
PF Coupe
Re: No good coil
Hi John, I once cured a spotty running condition on my car by cleaning and securing all the connections on the resistors. Also a good idea to clean the coil towers themselves as arcing can occur there. Good luck ,Mike
72,365gtc4,14681,2007 599 GTB
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- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: No good coil
Thanks Mike, will do. The resistor for these coils is the "tootsie roll" style and they are hardwired internally.
john
john
PF Coupe
Re: No good coil
Greetings... If points are open, no current flow and no heat. It is entirely possible for the engine to have one disributor open and one closed and the closed one will heat up the resistor and the coil whilst the open one will remain cool.John Vardanian wrote:Hi Dyke, how would the engine run if one of the distributor resistors was bad?
I am going thru things and noticed that with the ignition key on only one of the resistors gets hot. The other is quite cold. So, looking at your average ignition diagram on the internet, the resistor and the primary winding of the coil are in series, so if the resistor does get juice thru it neither does the primary coil, right?
john
Tim
1964 330GT 5769 -the big yellow taxi 61&66 Morgan +4's Daimler SP250 Turner 950S and some other dull stuff plus a brand Mercedes C300 4matic
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- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: No good coil
Hi Tim, you're absolutely right. Pardon my oversight.
Another question... with the points closed, shouldn't the voltage reading across the system be 6 volts, considering the effect of the ballast resistor, why do I get 12 volts?
john
Another question... with the points closed, shouldn't the voltage reading across the system be 6 volts, considering the effect of the ballast resistor, why do I get 12 volts?
john
PF Coupe
Re: No good coil
Greetings.. Where are you measuring. With points open and resistor and coil in the circut, I think you should get about 9V from the hot side of the points to ground. Remember, voltage is potential so you don't need current flow-except for the little bit through the meter.
Tim
Tim
1964 330GT 5769 -the big yellow taxi 61&66 Morgan +4's Daimler SP250 Turner 950S and some other dull stuff plus a brand Mercedes C300 4matic
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- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: No good coil
So, the problem wasn't the coils after all, it was one of the points in the right distributor. The edge of the leaf spring was touching the movable plate's lock-down screw and intermittently shorting the entire distributor. This, in spite of the electrical tape I had wrapped around the springs a couple of years ago when I serviced the distributors. Does anyone have a better idea? Thanks.
john
john
PF Coupe
Re: No good coil
Hi John, without seeing it I'm not sure about this suggestion. Sometimes the arm will ride up or down on the post.A small O ring stretched over the post or a plastic or fiber washer split and placed under the point arm should keep it above the screw. Could you use a screw that has a head that protrudes less? Good luck ,Mike
72,365gtc4,14681,2007 599 GTB
Re: No good coil
John: Afwrench is correct. You should have fiber washers both above and below the movable point arm. This should raise the arm away from the screw head.
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- Posts: 1908
- Joined: Wed Sep 04, 2002 12:13 am
- Location: San Francisco Area
Re: No good coil
Thanks Dyke and Mike. Yes, no doubt the fiber washers are in place. This last set of points I got, after putting them together I noticed one point doesn't center the complimenting point, so I added another layer of shimming to get them centered.
Mike, to your question, the problem came about during adjustment, from my screwdriver blade scraping against the electrical tape. The screws are the "panhead" style. If I shaved from the top or even from the diameter of the head the problem may well go away.
john
Mike, to your question, the problem came about during adjustment, from my screwdriver blade scraping against the electrical tape. The screws are the "panhead" style. If I shaved from the top or even from the diameter of the head the problem may well go away.
john
PF Coupe