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post #1 of (permalink) Old 10-22-2002, 09:02 PM Thread Starter
 
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quick question about wires from the coil

OK, I just posted about some electrical problems and Jaffer helped me clear up some stuff. but I've still got one unanswered question. I did a search but couldn't find what I was looking for. See the attached PIC for a very simple version of the wiring according to the haynes manual. The part in question is the Capacitor Jumper. It's supposed to be connected to the Red with tracer wire. But, what does it do? where does it go from there (if anywhere) and the ultimate question, DO WE NEED IT??? The wire is just haning there without the capacitor on it....will the jeep still start and run ok? here's the specs real quick Cj-5 with 304 V8 engine....76 or 77 as far as we can tell...has Motorcraft alt. and Prestolite ignition system. Please let me know.....sooo close to getting this thing going

Thanks,
--Jason
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post #2 of (permalink) Old 10-22-2002, 09:55 PM
 
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Re: quick question about wires from the coil

Not sure what will happen if its not there.I'm sure there is a reason for it.It is not part of the red/white wire it looks like a condenser and bolts on the coil bracket if you have the specs for it Napa should beable to look one up if you can get them to open up the book rather then just look at the computer.
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post #3 of (permalink) Old 10-23-2002, 01:38 AM
 
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Re: quick question about wires from the coil

howdy,
I've come to the same snag with my team rush up grade. none of the schematics I've found show the cap. My 89YJ has the cap connected to the old coil bracket.

Any how, I read once that the cap is there to absorb some of the energy released during the field collapse in the primary of the coil (when the coil is triggered to fire). What I have found is in reference to reducing the likely hood of arching the points ( when is the last time that you changed points?). So If you have points, then yes. If you have Dura spark or other breaker less ignition, then it might have little affect. I've also read I few comments about forming a resonance circuit with the primary, but I don't know why.

seems like I should know this [img]images/graemlins/confused.gif[/img] but, I post if I figure it out.
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post #4 of (permalink) Old 10-23-2002, 06:04 AM
 
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Re: quick question about wires from the coil

speedbuggy, you may very well be correct about the importance of the condensor with a points ignition. When TR explained it to me, he told me that it was there to help filter out radio noise caused by the coil. Mine is not connected, and the Jeep runs.
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post #5 of (permalink) Old 10-23-2002, 03:30 PM Thread Starter
 
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Re: quick question about wires from the coil

I've also heard similar claims that it's only for reducing radio noise. Although I've also heard that it HAS to be hitched up to make the Jeep run right.....so I'm confused....although it sounds like we don't really need it.
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post #6 of (permalink) Old 10-23-2002, 06:58 PM Thread Starter
 
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Re: quick question about wires from the coil

ALLLOCKEDUP is your system a prestolite system?? From what I understand from the info I got a few hours ago...it is need to smoothen out the flow of electricity......It works in the same way as any other cap would work...taking in extra voltage and letting out voltage when the voltage from the coil is to low. So I THINK we need to hitch this up for it to run smooth and charge correctly. Any more input would be appreciated...THANX
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post #7 of (permalink) Old 10-23-2002, 07:36 PM
 
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Re: quick question about wires from the coil

I hadn't heard about the importance of using the condensor with the Presolite ignition until someone (you?) brought it up. I have the Motorcraft system, and I can tell you that it runs fine without the condensor hooks up. The person to ask arond here would be TeamRush, but he's on hiatus. RRich knows his stuff, you may want to shoot him a PM and ask.
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post #8 of (permalink) Old 10-23-2002, 07:46 PM
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Re: quick question about wires from the coil

An ignition coil is an auto transformer. This means it has only one winding and the primary system charges only a tiny portion of it. When the primary cuts off the power, the characteristics of a coil try to keep the current flowing at the original rate. It flows through the larger, secondary portion of the coil looking for a path to keep the current flowing and creates a high voltage. This is when you get the spark, when the voltage is removed from the primary.

As to the capacitor, I've seen very few points systems that would not run without the capacitor. Usually it just reduces radio noise but it appeared that some coils had too quick a discharge period without it and never provided proper spark. With electronic ignition, the capacitor can prevent spiking the solid state switching device.

If it were a points system, I'd say try it without, what could it hurt. But since I seem to remember from the other post it's a '76-'77 with electronic ignition I'd say try to find the capacitor. Without it, you could ruin the module though I'd think it would have internal protection but that's beyond my field of expertise. So, I guess it's down to the question of Dirty Harry, "Do you feel lucky, punk?" (No disrespect intended)
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post #9 of (permalink) Old 10-23-2002, 07:50 PM Thread Starter
 
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Re: quick question about wires from the coil

Thanks taz, sounds like that's the answer I was looking for...it certainly is an electronic ignition (not points) so I think we're gonna try to find a Cap somewhere........dunno where yet
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post #10 of (permalink) Old 10-23-2002, 08:43 PM
 
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Re: quick question about wires from the coil

I would definately find one. Those older electronic ignition systems can be kinda sensitive to the gigantic line noise that can come from a coil firing. Personally, I would hook one up. Usually they are called something like a "supression capacitor" or something like that. I have a feeling that in a pinch, you could use a plain 'ole condensor.

If you don't have it, you will most definately hear the engine through your AM radio and your Cb if you have one......

Best regards

John
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