Burning up coils
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Burning up coils
I have a 1984 F250 with a 2v 351w and a EEC-IV ignition system.
I am frying coils over and over. My last one lasted 15 minutes.
I have replaced the distributor, ignition module, voltage regulator, and main computer. I continue to burn up coils. From smoking to just getting hot where the ohms are out of tolerance afterward.
I think the coil is getting a coninuous 12v even whie it is running. i believe that the voltage is supposed to drop while it is running. What could this be?
Please help!
I am frying coils over and over. My last one lasted 15 minutes.
I have replaced the distributor, ignition module, voltage regulator, and main computer. I continue to burn up coils. From smoking to just getting hot where the ohms are out of tolerance afterward.
I think the coil is getting a coninuous 12v even whie it is running. i believe that the voltage is supposed to drop while it is running. What could this be?
Please help!
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From: Virginia
Well, the TFI is supposed to get a full 12 volts, as well as the coil, with no resistor. I would get it running and check the voltage at the coil and also at the battery. See if the alternator may be going crazy.
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The voltage is getting about 12v. I determined that before I fired the last coil. The primary voltage wires got hot. Forgot to mention that. But I think the voltage is correct, unles it is supposed to be less than 12v like some people have thoguht.
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From: Virginia
The duraspark II units and the old points systems did have a resistor to drop the voltage. But the TFI system regulates the current electronically, so it doesn't have a resistor.
I can't think of anything that would cause this except maybe a grounding problem. Does the engine actually run?
I can't think of anything that would cause this except maybe a grounding problem. Does the engine actually run?
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Runs great... Until the coil fries... Runs like normal and then we've got a hot primary voltage wire, possible a smoking coil, and a coil that no longer works.
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Im no expert, but maybe you have too much resistance in the grounds and/or your TFI regulator is going bad.
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Originally Posted by moxy123
Possible the wires are hooked to the wrong terminals?
I'm happy everyone is having a tough time with this. I mean... where's the fun in asking easy questions...
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From: Virginia
I discovered something. The hot wire to the coil is white/lightblue. The negative to the coil is darkgreen/yellow. If you follow this darkgreen/yellow wire back, it hits a splice and goes 3 different directions.
Direction 1 goes to the TFI module. This is what grounds the coil and makes it fire. This must be working.
Direction 2 goes to the computer with a resistor. I am not sure what this is for.
Direction 3 goes to the tach in the dash. Does your tach work? This is what I would suspect first, that there is something wrong with the tach or the wiring to the tach, and it's drawing too much current through the circuit.
I would check all these darkgreen/yellow wires and possibly try to disconnect the tach to see if that makes the problem go away.
Also, if you just had a stereo installed, or some other aftermarket component, make sure this darkgreen/yellow wire has not been tapped into by mistake.
Direction 1 goes to the TFI module. This is what grounds the coil and makes it fire. This must be working.
Direction 2 goes to the computer with a resistor. I am not sure what this is for.
Direction 3 goes to the tach in the dash. Does your tach work? This is what I would suspect first, that there is something wrong with the tach or the wiring to the tach, and it's drawing too much current through the circuit.
I would check all these darkgreen/yellow wires and possibly try to disconnect the tach to see if that makes the problem go away.
Also, if you just had a stereo installed, or some other aftermarket component, make sure this darkgreen/yellow wire has not been tapped into by mistake.
Last edited by Franklin2; Dec 28, 2007 at 10:33 AM.
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How quick do they burn up after they are used.
The coils primary is designed to run at 12 volts or so with the negative terminal pulsed to ground by the ignition module to exite the secondary and generate a spark.
Some systems use 10 volt coils and use a large resistor to drop the voltage down from 12 volts while running and bypass it while starting to make up for the lower voltage while cranking.
This is general info and I do not know the specifics of that system. If this applies then even with the slightly incorrect voltage the coil should run hundreds of hours while being somewhat hotter.
Are you sure the case is not being damaged when installing the coil somehow, is it plastic or metal?
What is the voltage at the plus terminal and negative terminal with the key on but the engine not running?
What is the voltage on the plus terminal while the engine is running?
How large is the resistor that you speak of that goes to the ECU?
Are you buying them at the same place every time, maybe a batch of bad ones?
How did it fail in the first place?
The coils primary is designed to run at 12 volts or so with the negative terminal pulsed to ground by the ignition module to exite the secondary and generate a spark.
Some systems use 10 volt coils and use a large resistor to drop the voltage down from 12 volts while running and bypass it while starting to make up for the lower voltage while cranking.
This is general info and I do not know the specifics of that system. If this applies then even with the slightly incorrect voltage the coil should run hundreds of hours while being somewhat hotter.
Are you sure the case is not being damaged when installing the coil somehow, is it plastic or metal?
What is the voltage at the plus terminal and negative terminal with the key on but the engine not running?
What is the voltage on the plus terminal while the engine is running?
How large is the resistor that you speak of that goes to the ECU?
Are you buying them at the same place every time, maybe a batch of bad ones?
How did it fail in the first place?