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On 20 Dec 2004 16:52:07 -0800, "wtbuck12"
wrote: Dave Hall wrote: On 19 Dec 2004 19:24:09 -0800, wrote: I have an early 1980's modle 318 Chrysler engine installed in a mudboat. About 2 years ago I developed a problem with the Ignition coil burning up. The engine has the original electronic ignition system installed, but has been completely rewired by a Dodge dealership, the control module, ballast resistor, and the distributor pick-up assy. have been replaced. However, I continue to have the problem. The engine runs perfectly for about 3 months and then without any warning, will backfire and die. There will be no ignition fire until the coil is replace, then the engine will start up and run fine for another few months. Any help or suggestions with this problem would be GREATLY appreciated. Sounds to me like your coil is being "fried" because there is too much voltage being run through it. Most coils are designed to run at the full 12V when starting, but then switch in a dropping resistor which drops the voltage down to about 8V when running. If this dropping resistor is absent, the coil will get the full charge at all times. Another thing to check is your charging voltage. If your alternator regulator is acting up, and the charge voltage runs up to 16 or 17 V the same thing could happen. Although, you'd probably notice your batteries boiling over and very bright lights as well. Dave I appreciate all the responses very much. The resistor resistance is app. 1.2 ohms and running voltage is 8.2 volts. Alternator output is 14.4 volts. The coil is mounted directly to the block and the bracket seems to be tight and clean, no signs of corrision. I tried install a higher resistance resistor and dropped the running voltage to 7 volts, but that made the ign. fire too weak. I have tried using Mopar coils as well as aftermarket coils with no noticeable differance. Someone suggested using a HEAVY DUTY coil, where can I buy one and what do I ask for? This problem certainly has myself, the Dodge dealership and several local independent mechanics scratching our heads. Well, Sherlock Holmes once said something along the lines that when you eliminate the obvious, what's left, no matter how improbable, must be the answer. If your operating voltage is correct, and the coil is mounted properly and not exposed to the corrosive effects of water then I have to think that perhaps the shape of the ignition pulse is too sharp. If there is a sharp spike, which exceeds the operating voltage, over a period of time, it could cause the insulation in the coil to break down. The only way to see this is with an oscilloscope. The cure is simple though, a capacitor from the "cold" side of the coil to ground, somewhere around .1uF should do it. Dave |
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