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burning out coils

3K views 11 replies 6 participants last post by  cobalt327 
#1 ·
I have 1984 chevy p/u and have shorted out 2 coils in three wks.
dont know why.
 
#2 ·
You should have a resistor mounted on the firewall or near the coil. It is a ceramic type a couple inches long. These are used to lower the voltage to the coil after startup to about 8 volts which allows the coil to last longer. If for some reason your coil has been jumpered around the resistor, that could be why.
 
#3 ·
S10 Racer said:
You should have a resistor mounted on the firewall or near the coil. It is a ceramic type a couple inches long. These are used to lower the voltage to the coil after startup to about 8 volts which allows the coil to last longer. If for some reason your coil has been jumpered around the resistor, that could be why.
Not on a stock '84 truck with an HEI, ballast resistor is pre-'75 vehicles with points distributors.

To the OP - is this the stock HEI distributor in this truck??
 
#7 ·
kfence said:
replaced module. only resistor inside next to module
That's probably the capacitor for reducing radio interference, shouldn't affect the coil, you can disconnect it to see- possibly a prob. if it was internally shorted to ground, maybe- but doubtful.

Coils aren't known for failing, if there's been any electrical work done under the hood, I'd suggest you go back over everything.
 
#8 · (Edited)
Check the engine ground, if it is not clean and tight it can cause more current to be drawn through the coil to compensate for the bad connection.
Also what is the feed voltage at the HEI batt terminal. If it is over 15V you can burn coils.
Are you using quality replacements like an AC Delco or the Autozone house brand.
 
#12 ·
The spring that makes the contact between the coil and the carbon electrode to the rotor and the electrode itself can be burned out and/or damaged. This is located under the distributor cap, where the large rubber washer is located. There should be dielectric grease on the washer side that faces the cap.

The metal strap is used in some HEI's under the coil, others have a wire. This must be in place.
 
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