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Old 05-04-2011, 08:16 PM
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no spark

I've got a problem that I can't figure out and it is driving me crazy. I'm getting no spark at the plugs. Coil (Mallory promaster coil) has been tested and is good, 12.4 volts on + lead, 12.2 volts on the coil wire, grounds are good and a new Mallory Unilite distributor ran when the motor was built and mounted on a dyno. Voltage at the plug drops to 9 when the motor is cranking. There is no spark at the plug and its driving us crazy.

Out of beer, time to ask the experts. Any help would be appreciated.

Thanks,

67 Camaro RS, SBC 350

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Old 05-04-2011, 09:24 PM
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Is this a breaker-points style distributor or electronic ignition?

Assuming a points / condensor ...
Does the coil say "external" or "internal" resistor?

If "external", I believe that you should be seeing around 6 or 7 Volts at the + coil (primary ignition) terminal in the run position, and ~12V while cranking.

Check to see that the points are actually opening and closing. Gap at around 0.017" to make it run, then adjust using a dwell tach.

9 volts at the spark plug?

If you were to hook a test light up to the "-" side of the coil, you should see the bulb cycling from bright to dim while cranking, indicating the opening and closing of the contact points.

If you hold the coil wire just off the top of the center distributor cap tower, you should be seeing a bright blue spark and hearing an audible "snap".
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Old 05-04-2011, 09:43 PM
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Electric ignition, no points. Just don't understand how the coil is good but hooked up and I'm not getting spark?
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Old 05-04-2011, 10:09 PM
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I'm not sure if this is what you're working with, but there is a ballast resistor pictured with this coil. Running without it at 12V continuously would not be a good thing ...

Most big-city parts stores should be able to test that coil and perhaps ignition module also.

Installation / wiring instructions
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Old 05-05-2011, 01:37 PM
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Right now I don't have the inline resistor...getting one today. Even without shouldn't I still get spark? My only guess is if the resistor doesn't remedy the issue then I will have to pull the distributor and see if something is wrong inside.

Thanks for the help GMC!
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Old 05-05-2011, 10:45 PM
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This is purely speculative ... but as I said earlier, the entire ignition system (coil AND distributor) are designed to run on less than 12 volts, with the possible exception of cranking.

A distributor's primary function (related to the coil) is to provide an "on/off" pulse that charges/fires the ignition coil, and there are at least 3 methods of doing so that I am aware of.
Contact Points (mechanical switch), Armature/Reluctor (magnetic), and hall-effect switch (light).

Points:
A consistant 12V will begin to generate too much heat. Back in the old days, that 12V would turn a set of points blue and cause metal to be transferred from one contact to the other. It could be "fixed" using a point file and re-adjustment of the point gap.

Amature/Reluctor:
Electronic components, (i.e.modules) on the other hand are far less forgiving.
The reluctor (or "pole peice") if equipped, is not a lot more than an electromagnet that uses fine strands of insulated magnet wire. Too much heat there melts the insulation and ... pffft.

Hall-Effect:
A hall-effect switch uses light to provide the "on/off" pulse that loads and fires the coil. I would expect that this version would be the most forgiving as the "lamp" (LED or Laser? Not sure) would likely be more tolerant than those windings ... but there is still a module in play with that system.

In any case ... my somewhat educated guess is that you may have to replace some relatively expensive electronic components.
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Old 05-06-2011, 07:17 AM
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no spark

a friend of mine had a big problem similar to yours... he used the intake manf bolt for ground.. it appears it was a bad one and moved to the engine block.. no more problems...
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