Ignition Coil Overheat

I have an old jeep with an 302 ford engine in it & I keep burning up the 12 volt accel ignition coil that is mounted on the firewall. I have checked the wire connections & the vehicle ground & they appear to be good. Does anyone have any suggestions? This is my third coil I have put on....

Reply to
robert.prosser
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I was told by Accel that I still needed the ballast wire in the Jeep ignition wiring when running my Accel Supercoil which cuts the running voltage down. The coil will run on either alternator voltage or the lowered ballast wire voltage. I wanted as 'hot' a spark as I could get so asked about it. They mentioned I would have ignition module issues with overheating though.

Are you sure the ground is good? Jeeps are bad for losing the body ground and having ground theft through other paths happen. The 6's have a mesh ground strap from the engine head to the firewall as well as a mesh strap across one engine mount to ground the frame. The mesh one to the firewall gets rotten easy. I also have seen the main ignition ground via the distributor go bad. Basically the hold down foot for the distributor is one main ground path and it gets rusty. I have my coil right on the block by the dipstick but I have a 258 six. It is over 6 years old now and runs strong still.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Hmmm... you should probably read up on coils and ballast resistors a little. If your coil is designed use with an external resistor, you need to use one for sure. (BTW, coils for use without ballast resistors usually have one built within the coil itself) Running without a ballast is usually tough on points too.

Also, on the block is a terrible place to mount the coil. All those heavy copper windings don't do well with the extra engine vibration. Try to avoid areas close to exhaust manifolds and other hostile areas as best you can too.

Good Luck,

Erik

Reply to
Erik

I actually asked Accel about their SuperCoil. It can run with 'either' voltage.

If the OP has one that is only set up for a ballast line voltage and he doesn't have it, it will burn out.

Mike

Reply to
Mike Romain

Maybe your dwell time is set too high, oversaturating the coil..

Reply to
corning_d3

Not necessarily, it depends on the rest of the ignition systems. CD ignitions don't use ballast resistors, either inside the coil or outside. Neither does GM HEI.

Reply to
Steve

Normally if the dwell is really far off, you see other indications.

Reply to
<HLS

Don't know what you mean by 'either' voltage. Having a ballast resister or resister wire doesn't change the voltage to the coil in any measurable way. It does reduce the current (and temperature). You would need 2 resisters one to the coil and one to ground to reduce the voltage input.

-jim

Reply to
jim

Reducing the ignition primary voltage is exactly what a ballast resistor accomplishes. Battery/coil ignition systems didn't change appreciably when most manufacturers switched to 12 volts from the previous 6, back in the '50s. They just added a resistance, and continued using the same coils. Most systems used a bypass circuit to supply full battery voltage to the ignition during cranking. Provided a little more energy to fire plugs when the engine was cold and the mixture was more difficult to light. When the start motor was disengaged, the resistor came back into play, stepping the voltage down to about 8 volts.

Reply to
the fly

Not on any I have seen.

When I turn my Jeep ignition to 'start', I have a 12.6 (battery) volt feed from my starter solenoid directly to the coil.

When I then turn my ignition to 'run', a second circuit cuts in with a ballast wire or resistor wire. In the CJ7's case, it is a 1.35 ohm resistance wire. This drops the battery voltage down to 9 or 10 volts from the 12.6 is should be. With the engine running, it drops the alternator voltage down the same percent.

The Accel Supercoil can run on either the volts the alternator puts out or the lowered ballast voltage according to Accel.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

On old GM's that had points, there were two terminals on the starter - one that fed the ballast, and one that bypassed it for starting the car with full battery voltage.

Reply to
ray

Got a radio?

Reply to
Ibn Fadlan

| I keep burning up the 12 volt accel ignition coil

Is this an induction coil or transformer ?

Reply to
TE Chea

The starter also draws huge amounts of current, dropping system voltage while in use. The bypass circuit compensates.

Without a ballast resistor bypass, starts would especially difficult with a partially discharged battery.

Erik

Reply to
Erik

Yes I guess when the points are closed you do see the voltage drop. But not when the points are open. Then the measured voltage should still be the same as battery voltage. When the engine is running the peak voltage can't really be accurately measured with a DC meter. Anyway, the resister is limiting the current which which is what causes the coil to heat, which I believe was the topic of discussion.

-jim

Reply to
jim

They say a picture is worth a thousand words;

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Where would we see the ballast resistor drop voltage?

Before transistor turn on/points close? Nope, voltage is clearly system voltage.

After transistor turn on/points close? Nope, voltage is already being pulled to ground by the transistor/closed points.

Reply to
aarcuda69062

You have absolutely no idea what a resistor does or how a coil works do you?

The coil gets a stable positive voltage that can be measured with any multimeter or even a VOM when referenced to the battery ground.

We even hook the coil up 'directly' to the battery positive with a jumper cable to test for a bad solenoid or resistor wire.

The points or in my case ignition module only affects the coil's negative feed. They pulse the negative in time to the engine to give you spark. You would need a fast meter to measure this pulsing of the 'negative', but any meter or even a light bulb will tell you if the coil has power...

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
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(More Off Road album links at bottom of the view page)
Reply to
Mike Romain

With the points closed, the voltage measured at the coil positive will be lowered. It's measurable because the resistor's decreasing of the current though it will cause a voltage drop. The resistance of the coil prevents a full drop to ground potential. You will NOT find zero voltage at the coil positive with points closed; that would represent a short circuit through the coil and heating would be a huge problem, to say nothing of the fact that no work would be getting done. You'd burn out wiring instantly. Zero potential will be found only at the coil's negative terminal with points closed (unless they're burned and need replacement). I went through all this recently while restoring my '51 International. I had to install a 12-volt system but stayed with points and condenser ignition, and used a nichrome heater motor resistor to get the 5-volt drop. I don't like resistor wires (or fusible links, either) because they fail due to vibration and can be hard to find. And I teach it in college aircraft systems courses. You might want to review Ohm's law. Dan

Reply to
Dan_Thomas_nospam

Correct.

But the purpose is not to get a voltage drop. If you discuss voltage drop you at least need to be clear about when in the ignition cycle that happens. The purpose is to reduce current. The voltage doesn't matter. In fact while the car is running the effect of having a resister in the circuit to the positive terminal of the coil actually increases the voltage to a higher level than the battery voltage *some of the time*, but it would be just as incorrect to claim the purpose of the resister is to increase voltage just because it happens during part of the ignition cycle.

-jim

Reply to
jim

First check the ground connection thoroughly. If the jeep is used offroad there's a good chance you have a poor or even intermittent ground. Next, try replacing the Accel Super-Duper coil with the standard Ford ignition coil and I'll bet the burned coil problem goes away.

Reply to
John S.

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