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Discussion Topic:
Proper ignition coil wiring
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Junglejim |
06-12-2020 @ 11:17 PM
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Member
Posts: 17
Joined: Jun 2020
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Hey y'all, I'm new here and am trying to trouble shoot my '37 flathead. It will turn over but wint fire. Carburetor gets fuel. I have installed a 6v fuel pump and a fella that rebuilt the engine back in 2003 put an aftermarket distributor and ignition coil in. I have removed a spark plug and get very poor arc, I suspect it's my ignition coil, which I noticed had the wire that came from the firewall hooked to the positive pole of the coil and the other wire connected to the negative. Is this wrong? 6v positive ground, the wiring should be flipped. Could some one inform me properly on how to hook up my ignition coil? Jim
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40 Coupe |
06-13-2020 @ 7:36 AM
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Senior
Posts: 1679
Joined: Oct 2009
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If your battery is connected + to ground then the coil + should go to ground, that is the wire going to the distributor points. Another source of poor spark could be the resistance of the primary of the coil you have. Ford has a 0.5 ohm resistor under the dash for their original coil which had a primary resistance of about 0.5 ohm. If your coil has the same approximate primary resistance then use the ford resistor if it is 1.0 ohm primary resistance there is no need for the Ford resistor and it should be bypassed.
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Junglejim |
06-13-2020 @ 9:16 AM
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Member
Posts: 17
Joined: Jun 2020
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Thanks for the info. I cannot see where a resistor is on I'm my car, but I will continue to look. What is the life expectancy of an ignition coil? Jim
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carcrazy |
06-13-2020 @ 11:03 AM
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Senior
Posts: 1674
Joined: Oct 2009
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The ignition resistor should be mounted up under the instrument panel inside the passenger compartment. The wire from the ignition switch mounts to one side of the resistor when using a stock original 1937 Ford coil and the wire that goes to the ignition coil mounts to the other side of the resistor. When using an aftermarket cylindrical 6V coil you should bypass this resistor by either mounting both wires to the same terminal of the resistor or using one new wire to go directly from the switch to the coil. Buy a quality coil and it should last a long time. Always carry a spare coil with you in case the one on the engine fails. I have had new coils fail in as little as 10 minutes.
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Junglejim |
06-13-2020 @ 11:56 AM
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Member
Posts: 17
Joined: Jun 2020
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Thanks senior, Where do you purchase your coils? Jim
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carcrazy |
06-13-2020 @ 9:25 PM
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Senior
Posts: 1674
Joined: Oct 2009
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I have bought coils from many sources and found that cheap coils do not last very long. One source that I trust to sell a quality coil is Fifthavenuegarage.com. Randy Rundle who prepares cars to run in the Great Race sells a 6V Coil, P.N. 954156C for $80. You can buy coils for as little as $20 elsewhere but I find that you get what you pay for.
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Big Red 51 |
06-14-2020 @ 2:48 AM
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New Member
Posts: 192
Joined: Oct 2009
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Car Crazy, Is it possible to check electrically an ignition coil with built-in resistor for working? I use the NAPA Echlin IC 7 coil on my 8BA engine with stock distributor. About every three years, in hot weather driving, the engine stumbles and dies. At first I thought it was a fuel problem or just bad ethenol gas. Fuel system is clean and tight. I finally installed a new Echlin coil and I am good for another 3 years at about 2 or 3 thousand miles on average with plenty of hot weather driving. Never a problem otherwise. Thus, I would like to test the coil for functioning under load with high heat to see if it really is the coil. Thanks, Big Red
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1931 Flamingo |
06-14-2020 @ 5:34 AM
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Member
Posts: 388
Joined: Nov 2019
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Interesting: Coil failure vs. condenser............... Paul in CT
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TomO |
06-14-2020 @ 9:30 AM
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Senior
Posts: 7256
Joined: Oct 2009
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Big Red, you can test the coil for heat break down by removing the coil wire from the distributor cap and holding it near a good ground while turning over the engine to check the spark. If the spark jumps about 1/2" and is blue in color, continue with the heat test. If you do not get a good spark, try checking or replacing the condenser. Heat test: Tap the starter until the points are closed and turn on the ignition for 4-5 minutes. Recheck the spark, it should be the same as the first test. If it is significantly weaker, get rid of the coil before it strands you. I have seen new coils fail this test, but when they pass it they last a long time. Jim, the best test for an external resister is to tap the starter until the points are closed, turn on the ignition switch and measure the voltage at the input to the coil. It should be near battery voltage, if it is less, you have resistance in the primary circuit. Check your spark like I described for Big Red.
Tom
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JayChicago |
06-14-2020 @ 10:03 AM
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Member
Posts: 486
Joined: Jan 2016
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"Interesting: Coil failure vs. condenser............... Paul in CT" Yes, this can be confusing. From what I understand, they both give similar symptoms: weak spark, more likely to show itself when warm, may work again after cool-down. TomO, do you have a thought on this? Am I correct about the symptoms being about the same? Or does a bad condenser give weak spark hot or cold. When we are faced with a weak spark condition, is there something to indicate the coil vs. the condenser?
This message was edited by JayChicago on 6-14-20 @ 10:06 AM
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