| Junglejim | -- 06-12-2020 @ 11:17 PM |
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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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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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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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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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Thanks senior, Where do you purchase your coils? Jim
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| carcrazy | -- 06-13-2020 @ 9:25 PM |
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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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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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Interesting: Coil failure vs. condenser............... Paul in CT
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| TomO | -- 06-14-2020 @ 9:30 AM |
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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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"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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| carcrazy | -- 06-14-2020 @ 4:53 PM |
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In my experience when the coil is about to fail, the engine will fire up from cold and run alright for about 10 minutes until the engine warms up. The car will then have no spark until the engine has cooled down for 1/2 hour or more, then it will start and run again until it heats up and the same thing will happen again. When the condenser goes bad the engine will stall and will never run again until the condenser is replaced with a good one.
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| Junglejim | -- 06-15-2020 @ 11:00 AM |
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So, I tested the resistance on the current coil I have, it seems to be fine. So in regards to the condenser, where is that located? On the distributor? Are condensers all created equal? Thanks Jim
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| JayChicago | -- 06-15-2020 @ 1:37 PM |
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Yes, on the distributor. You can see the condenser in the first picture you posted. Is the drum-shaped piece about two inches long. It has small bolt holding to distributor case, which also provides the condenser's ground path. The condenser's input wire attaches to the same terminal as your purple wire from coil. I understand most condensers are pretty much the same, and the little differences in capacitance won't matter to your car. And same condenser will work on 6 volt or 12 volt cars. However, I also understand many new condensers bought from the usual sources are defective right out of the box! I have read many V8 guys saying you can rely on NAPA #FA 54 to work properly.
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| 37RAGTOPMAN | -- 06-16-2020 @ 4:35 PM |
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HI carcrazy I have seen the same problem, with no spark when hot, or missing., what you can do to see if it is a coil or condenser, try a ice pack on the coil, and see if you have spark, this got me home a few times, this works, also you can spray something cold on the condenser, trying to isolate the problem, to see what exactly it is, also by passing the ignition switch with a jumper lead, is also a way you can check if the switch is working, maybe dirty or worn, this does happen more times then you think, my 2 cents 37Ragtopman
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| Big Red 51 | -- 06-17-2020 @ 2:39 AM |
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Tom O Thanks for the test procedure on the coil. Seems as though another Echlin 7 coil has failed after only 18 month. The online NAPA parts site doesn't even list Echlin Ignition parts anymore in New Jersey plus no Napa Gold oil filter 1006 nor does my NAPA store stock them any more. Not sure what has happened to Echlin, moved to Asia???
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| TomO | -- 06-17-2020 @ 8:16 AM |
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Jim, did you try the coil test procedure in my previous post? It works well with point distributors, but is unreliable with the electronic distributors. If you have an electronic distributor, the original wiring that you posted may be correct. I don't have a good procedure to check out the electronic distributors. Tom
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| therunwaybehind | -- 06-17-2020 @ 9:12 AM |
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These rather unsure views are not unexpected when dealing with alternating current where a condenser is an "AC short." The primary side of the coil can be probed by DC voltmeters and resistance checked. The secondary side where the spark plug wire is stuck in the coil center and the other connection is inside the engine combustion chamber at the spark plug ground terminal is only connected to the primary by laminated steel in a magnetic core and depends on the variations of magnetic flux in the primary loops coupling with the induced (like that word?) magnetic flux in the secondary loops to not just complete the circuit but by relative loop count raise the voltage from 6 to in the ten thousands. Now that was all fine until solid state electronics was discovered where you could make gates by geometric deposition of thin films and not have to go through tedious field understanding. The kinds of first devices, diodes and transistors quickly produced circuits that could amplify audio at 9-12 volts. Their problem was called "thermal runaway." Once the circuit got above about 100 degrees Fahrenheit the behavior became highly unpredictable. As these devices ceased to be made from germanium for radios and stereos and became silicon power transistors they began to be looked for for control of automotive spark. This was about where I graduated from the University with one class in Electronics and where my more sophisticated roommate who was going to be a University Automotive Engineering professor began to experiment with transistor electronics on his 1955 car. Even with a highly modified engine in 1965, he tried to show the benefit of transistor circuits. He only got into trouble later with an AC alternator on a motorcycle wired up as an AC magneto. Remember the phrase "Energy Transfer" associated with factory attempts at that? The condenser's only purpose is to prevent the distributor points from arcing when they open and close and creating erosion and pitting. The appearance of the points is the clue to the lack of or improper value for the condenser. No need to go through a Kirchhoff's law analysis of the associated RC circuit. This message was edited by therunwaybehind on 6-17-20 @ 1:48 PM
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| Junglejim | -- 06-22-2020 @ 7:02 AM |
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Update, So i disconnected and cleaned all the connections for the ignition system, as well as the test procedure TomO suggested, and when I got it all back together with the positive pole of the ignition coil to the distributor(positive ground) she fired right up. Fires right up without hesitation since, so far short drives have been successful and am working my way up to longer ones as the opportunity presents itself. Now onto the generator...
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