396 big block no spark at plug../electrical issue? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-07-2011, 10:20 PM
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396 big block no spark at plug../electrical issue?

New to site, hope you all can help... here goes.
Just inherited a 1968 camaro with a big block 396 (from a 66 impala) with t400 tranny..no spark at plug. It is points distributor, but i dont see a resistor wire or ballast resistor. (new battery, starter, plugs, plug wires, coil, points, rotor, condenser). Now the problem,... car turns over fine, but no spark at plugs. There is thick gauge wire from battery to starter, one green wire from starter crimped to a purple wire that dives into firewall that im assuming goes to ignition, then white insulated wire that comes out of firewall to the pos of the coil. on neg side of coil there is a small black wire that goes to underside of distributor. i am getting 12v reading at the pos and neg of coil when key is in the on position. No spark from the high tension high voltage upper insulted wire that goes from coil to the distributor (when i take this wire off the distributor and hold it close to ground and turn key to crank, no spark fro it). points open and close when i crank engine, distributor seems to spin well (also i bypassed the ignition by placing a wire from pos side of battery to the pos side of coil, no spark), also i checked to see that the small black wire that goes from neg side of coil to the underneath side of the distributor was good and i think it is because i am getting 12v at the post inside the distributor. none of the 3 new coils that ive bought remedy the problem. I am not sure if it might be a fuse issue(doubt) or a resistor issue(doubt), or an electrical/grounding issue (i bet!!). UGH, must be an electrical wiring issue and something relatively simple since ive already replaced most of the electrical stuff. Thanks for your patience with me, obviously im sort of a newbie, but i am working on it with my 11 year old son and 8 year old son. we are ALL learning a lot!!! (especially me).. ...john

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Old 06-07-2011, 10:38 PM
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Check condensor.
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Old 06-08-2011, 07:38 AM
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Hard to read your post without any line breaks.

I would replace the points and condenser (cheap parts to change).

gap the points at 0.020" with the points open maximum position. (points on the peak of the distributor bump). Use a dwell meter to set the gap once you get the engine going.

measure the ohms on the coil. should be 1 to 2 ohms between the + and - posts.

make sure you have voltage at the coil when the engine is being cranked.

once the engine is running, the coil should have around 9V. A coil resistor should be used for this. Points get burnt up quickly if the voltage to the coil is too big (battery voltage).
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Old 06-08-2011, 09:41 PM
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Thanks for info..the points and condenser are new (i have tried several diff. condensers...and several diff. points). I will try to reset the gap (but i am confused how the gap being off would prevent power at the spark plug?) I can see misfires...rough idle, etc..but no power at all at spark plug? hhmm??
The coil is hot on both sides when cranking. I will check the ohms at the coil and write back, thanks so much!! I still think that it must be some type of ground problem or bad wire. Maybe i will try to buy some white insulated resistor wire and replace that white wire that goes from pos to the firewall/ignition. Maybe i am reading power at the coil with the test light but there is too much reistance in the wire? who knows? Thanks again...this journey will just make that first crank sooooo much sweeter!! Plus it will be a good opportunity to learn lots of things...like how to use a multimeter!! lol
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Old 06-09-2011, 09:21 AM
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if the points open too far or not at all then it will get no spark at the plugs.

take off the cap and rotor and bump the engine until the points are on one of the distributor bumps and set the gap with a feeler gage. This will get it close enough to start.

FYI, ignition wires typically have 1K ohms every foot. so a 3 foot wire will have 3K ohms.
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Old 06-09-2011, 10:00 AM
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hhmm good info, I will check the ohms on that white insulated reisistor wire that is taking power to the pos post on the coil. The points open and close just fine when i try to crank the engine...but maybe they are opening too much?? I will take your suggestion and try to regap the points and replace that white resistor wire and keep you posted. I will laugh my head off it was just poorly gapped points!! Thanks again all. Unfortunately, i have to go fishing to the keys for a couple of weeks and i wont get to work on her till i get back, but i will update on my return!! john
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