Electrical Help With 67 Fastback 390 Coil

Discussion in 'Classic Mustang Specific Tech' started by Scode67, Jul 30, 2013.


  1. Scode67

    Scode67 New Member

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    I have a 67 fastback with a 390. I am only reading 6.75 volts at the coil. Is this correct or do I have something faulty? I took a plug out to check the spark and it was not very strong or consistent. It was only firing every 2-3 seconds. Battery is charged, and it seems to be turning over ok. Could the battery be faulty and not cranking fast enough? 750cca battery
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  2. 2+2GT

    2+2GT Well-Known Member

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    About 7V while running is normal. The coil only gets 12V during start.
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  3. woodsnake

    woodsnake Active Member

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    Are you trying to diagnose a specific problem, or just learning in general?
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  4. Scode67

    Scode67 New Member

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    Hey, I am trying to get it to fire up, but it just don't seem to be firing properly. It has a new coil, new cap, new points, rotor button, new plugs and wires. The spark is not very strong when I pull a plug out and check it to ground. It ran a couple of years ago, and now it acts like it don't want to attempt to fire over even with fuel put into the carb. Seems like it should at least fire up for a couple of seconds. Any suggestions???
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  5. Scode67

    Scode67 New Member

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    Thanks, this was very helpful!!!!
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  6. woodsnake

    woodsnake Active Member

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    Well, back to basics....How old, and well charged is the battery? How old or worn out is the starter? Any chance the timing gear has slipped? Good clean battery connections? Tight, clean connections on the starter? On the coil itself? Fresh fuel? Does it try and sputter on like either, or brake cleaner?
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