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Old 03-28-2011, 12:19 AM
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Weak spark w/hei dist when hot!

Hey having a weird problem w/ my HEI Dist,when the engine gets hot I have weak spark and no start. I have 12v @ dist,new ignition module,cap,rotor,coil and didnt fix problem.So the only thing left was the pick up coil,new p/c installed and ran great for 2 days then same problem came back.12v @ dist. Thinking of putting in CDI to help w spark! Running out of ideas! Need help Thanks!
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Old 03-28-2011, 03:51 AM
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Mine kept burning out the Module, someone recommended that I swap out the old external reg to a newer internal reg in the alt...... been working good so far
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Old 03-28-2011, 04:50 AM
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This is kind of a long shot but maybe a ground issue. You might try a voltage drop test between the coil pos and the body of the distributor.
Or get it on an oscilloscope and see what's going on.
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Old 03-28-2011, 10:03 AM
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Quote:
Originally Posted by TheChvyGuy
Hey having a weird problem w/ my HEI Dist,when the engine gets hot I have weak spark and no start. I have 12v @ dist,new ignition module,cap,rotor,coil and didnt fix problem.So the only thing left was the pick up coil,new p/c installed and ran great for 2 days then same problem came back.12v @ dist. Thinking of putting in CDI to help w spark! Running out of ideas! Need help Thanks!
I'm wondering if your battery might be marginal. You could try cranking it w/a jumper to a good hot battery to see if it improves.
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Old 04-03-2011, 06:51 PM
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Seems like all new parts. A bad battery would/shouldnt be a problem when running beause the alternator is outputting

Possible its just a simple lose connection somewhere getting hot? Checked every wire, even plug wire, every stake-on connection etc?
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Old 04-03-2011, 07:30 PM
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Originally Posted by TheChvyGuy
...when the engine gets hot I have weak spark and no start.
Nada to do w/the alternator supplying current- the engine will not start in the first place.
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Old 04-03-2011, 07:46 PM
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I probably will fail to word this correctly so I hope you can get what I am trying to say. Although you are getting 12 volts at the dist., you may have a low amperage potential because of the wire having broken strands at the terminal. Just for a test run a wire from the battery to the dist + terminal using at least 12 gauge wire and see if it starts. JMO ........... Allan
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Old 04-03-2011, 08:13 PM
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AKA "hotwire" it.
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Old 04-04-2011, 03:53 AM
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New module.... runs good for a few days then starts funny stuff....hmmmmm, I'd try a 2nd new module, if that works then I'd think about the voltage reg
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Old 04-04-2011, 08:11 AM
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module

did you use a good brand of module and use the supplied grease under it when you screwed it down? I have had trouble with that before and finally went to a gm dealer for the module. when you replaced the coil, was the little ground strap or ground wire installed for the coil (goes from one of the coil mounting screws over to the main plug in on the distributor cap,and does it have a corresponding wire in the plug in from the car that goes to a good ground?). is the pink wire that supplies power to the dist. in good shape? a test light or multimeter only shows 12v, not the amperage that the wire will conduct. to test without fancy equipment, use a jumper wire from that pink wire and try plugging in something like the heater fan directly to that wire. does the fan run on high as fast as it should? you could bypass all that and just run a 12ga wire from the battery to the dist. and see what kind of spark you get then. how about body and engine grounds? connections at fuse panels, ignition switch and battery terminals? are the plug wires breaking down under heat-maybe try a known good wire to check for spark when you try it next time. is the coil overheating (telltale blue spots on the sides of the coil) that can cause heat soaking and diminished output? are you using the right spark plugs and gap (resistor plugs and big gap equals more spark output to jump the gap)? how is the fuel mixture (lean mixture is harder to ignite that a rich mixture)
after that, I dunno
keep us posted on what you find
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