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Old 12-02-2006, 04:38 AM
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Testing HEI Coil/Module

350 Chevy won't start!!!! Is there a way to test the coil and module to see which one needs replaced? I have 12-Volt at the Battery wire going to the distributor but she won't start!!!! I put one of those cross-fire caps/coils (puts 4-wires on each side) that makes a neat wire job on a show car about 3 years ago. Anyone had any experience with these caps as to failure verses the original cap with coil?

All input greatly appreciated. Thanks...........Ron

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Old 12-02-2006, 05:57 AM
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your auto store can test module
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Old 12-02-2006, 05:58 AM
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Doc here,

First be sure the 12 volts doesn't drop out when cranking..If it does you may need a secondary Ignition wire or a better source of power for the HEI.

The Module can be tested for free, at any Auto Zombie, and if it is bad...HAVE the new one checked..huge OBF's on those..and once you leave the store..It's your problem..Either way, re~installing or installing new, DO NOT forget the heat sink compound..or you will be doing it again real soon!

On the coil, Remove and invert the cap, Measure between the tach and BATT terminals , using a DVOM, Set to OHMS scale, RX1 and calibrated to 000. It should read less than an ohm, but more than 000, If not it's bad.

Next measure the secondary, set your DVOM scale to RX10k or higher..put the probes between the BATT and the carbon pickup for the COIL..it should read between 6000 and 30,000 OHMS..Outside of that range toss the coil and get a new one.



Check the Carbon pickup and spring follower, it may not be reaching the rotor pickup..or be worn or snapped past runout.

If that won't bring it to life, check the Magnetic pickup, by measuring the resistance across it. (you'll have to lookup the spec's for that year HEI..GM made a year divider on the pickups, and from a certain year Down were one resistance and a different resistance for that year and up..) If it is bad, you'll have to pull the distributer, and disassemble it to replace it.



Doc
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Old 12-02-2006, 04:22 PM
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It Works....

Bad coil!!!!!! Buddy brought over new coil and I put it in and it fired right up.....Thanks to all for your input and diagrams to test coil. Great site!!!!!!

Sweet-34.....Ron
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Old 12-02-2006, 04:29 PM
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Doc here,

KEWL!!

Glad to hear you got it fixed , and letting us know..

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Old 01-10-2011, 03:49 PM
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Is there any way an hei coil can be bad/weak but still run the motor?
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Old 04-10-2011, 12:59 PM
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with pictures

This post is equally good. I like it because there are pictures.(It helps me LOL)
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Old 04-10-2011, 04:21 PM
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Quote:
Originally Posted by norcal200486
Is there any way an hei coil can be bad/weak but still run the motor?
It is possible but pretty rare. A coil could go open or short when it gets hot.
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