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Old 04-04-2012, 08:53 PM
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HEI Ignition issues.

I've always used HEI's and never had any issue with them. However, dealing with one now that is in a restored 85 Corvette. The TPI and computer are still in use. It started out as it would run about 3 minutes then go dead and not start back. Spark test showed a really weak yellow spark.
Yanked it out, replaced the pickup coil, module, distributor cap and coil in cap. Reinstalled it, got it in time the car fired right up, ran about 3 seconds and went dead. Recheck spark, same thing, except this time it would spark every other revolution, again spark yellow and weak. Next was start swapping parts until one fixes it. Swapped modules, nothing. Swapped coils, nothing. Checked Voltage at hot wire, solid 12 volts. Checked the ground, looks good. The only thing left in the system is the spark control module, but I don't see why that would make it produce a really weak spark. It's been my experience in the past a weak spark was either the module or the coil. Checked the ohms on the pickup coil, they were in spec. Pickup coil has a strong magnitism to it. Stumped here, I dunno what else to check, any pointers would be appreciated.

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Old 04-04-2012, 09:11 PM
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Ground strap for the coil in place? Being a plastic car, might want to double check the ground is good at the connector and coil side of the distributor, and that the distributor body is grounded (check that the dist. is grounded from the neg. battery post or w/a 12VDC test light- clip to 12V, probe to dist. body)

If you want to try bypassing the electronic spark controller, if it has a four wire connector on the distributor unplug it and connect the green and black wires on the distributor side.

One other thing that comes to mind is to check the pigtail from where the module plugs in, to the connector at the other end to see there's continuity. The radio suppressor (looks like a condenser) isn't supposed to cause trouble, but you might want to check it to be sure it's not internally shorted.

Good luck, I know you'll figger it out.
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Old 04-05-2012, 04:24 PM
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Just a thought. Can you probe the wire feeding the distributor for 12V before you start it, leave it connected, and monitor it as its started by someone else. It may be a good 12v on initial firing, and the computer may turn on a relay for something else that is shorted/bad and pull the voltage down, but after the engine shuts off/key turned off, the relay de-energizes and the volts look good again?
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Old 04-05-2012, 07:05 PM
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Is there an anti-theft device on the car u don't no about. You no., like you have to flash the hi beams or turn the heater on or something like that. Just asking.
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