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Voltage at coil but no fire?

Voltage at coil but no fire?

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Old 10-06-2018, 03:31 PM
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Voltage at coil but no fire?

I have a 1971 Challenger, electronic ignition, which I put the orange ignition box on a couple of years ago. It ran fine, but won't start now. I have voltage at the coil, but no fire from the coil.

I replaced it with a black box with the "Electronic Ignition" sticker on the top (5 terminals). I have fire now, but it seems it might be weak. Not sure. But, the engine still will not start. The Ballast resitor seems fine, and is the single resistor type. Gas isn't an issue (unless it's flooded).

The voltage at the coil with the black box is about 7.5 volts (switch at run position, more when in the start position). With the orange box it's about 10.6 volts.

I haven't scrutinized how the system works. But why would the orange box have it showing voltage at the coil but still not fire? And why might the engine not start with the black box? I wonder if the 7.5 volts is not enough. I think it should be around 9 to 10, if I understand correctly.

Thanks very much.
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Old 10-06-2018, 04:59 PM
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By the way, my ballast resistor was for the black box. Resistance measures 1.5 Ohms. I understand that the proper resistor for the Orange and Chrome boxes should be between about 0.5 and 0.7 Ohms. Maybe I fried my orange box by having the wrong resistor?
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Old 10-06-2018, 05:50 PM
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Do you have good spark from the coil wire to ground? When you try that?
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Old 10-06-2018, 06:40 PM
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Meh. It seems weak to me. But it's there.
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Old 10-07-2018, 09:06 AM
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Sounds like it needs a new coil...
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