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post #1 of (permalink) Old 12-09-2001, 01:55 PM Thread Starter
 
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TFI voltage

How many volts does the TFI coil require. My cj only gets 8.6 to the coil, I'm guessing the TFI is a 12 volt coil, am I wrong. If it is 12 do I just run a new wire to the coil to get rid of the resistor?

'78 CJ7
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post #2 of (permalink) Old 12-09-2001, 02:26 PM
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Re: TFI voltage

a full 12 volts..just run a new wire

post #3 of (permalink) Old 12-09-2001, 03:21 PM
 
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Re: TFI voltage

I would assume you are getting 8.6 Volts running...?...

You need 1.35 Ohms total resistance in the coil circuit.
The coil it's self is about 0.45, and the factory ignition resistor wire is about 1.35 Ohms.
The extra resistance isn't going to hurt anything.

The coil should be working fine if you have 8.6 Volts at the positive terminal while it's running.

(if you think it's weak, just grab one of the plug wires!)[img]/wwwthreads_images/icons/shocked.gif[/img]

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post #4 of (permalink) Old 12-09-2001, 03:37 PM
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Re: TFI voltage

Tr I thought all the write ups said it was a full 12 volts...so thats how a wired mine...is it going to blow???

post #5 of (permalink) Old 12-09-2001, 09:05 PM Thread Starter
 
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Re: TFI voltage

Yes that was in the run position, but not running at the time. I would assume the voltage would be the same actually running or not, correct? Also when I asked for a coil for an 83 F150 with a 302, like the write up on swb.com lists, the guy came back with a regular old oil filled coil but the p/n from sorenson was correct. Thanks for the info TR and I won't be grabbin any plug wires, I'll take your word for it.


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post #6 of (permalink) Old 12-09-2001, 11:00 PM
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Re: TFI voltage

The fords for several years were made both ways...with "EEC" and without. The EEC coil is the one you want. The guy found one part number and stopped looking is what I suspect.


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post #7 of (permalink) Old 12-10-2001, 01:04 AM
 
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Re: TFI voltage

My parts guys still slip up and say, "...You want fries with that?" [img]/wwwthreads_images/icons/shocked.gif[/img]
----------------

I always said, "Full 12 volts" for the guys that had the factory Motorcraft/ DuraSpark ignition.
The resistor wire was already built into the harness, and it just confused a lot of people if I referred to current reduction via a resistor they couldn't see.

If you Jeep is a '78 through '90, it has the resistor wire.
If it is a '72 or older, it has a resistor in the harness somewhere, but that was a breaker point type ignition.

I haven't done the research on the Prestolite years to tell if they had a resistor or not...
(That was such a piece of crap for an ignition that even points were more reliable, so why waste any more time on it?)

If you haven't had any problems with your upgrade yet, you probably won't.
If you want to add a resistor, use a Chrysler 'brick' type (porcelain type, about 3 inches long) and just plumb it in the coil supply line. You are looking for a total of about 1.35 Ohms, and your (assuming) TFI style coil is about 0.45 Ohm, so you need about 0.90 Ohm up to 1.50 Ohm resistor.
If something gives, it will be the power transistors in the DuraSpark module...
(So carry a spare if you don't already... Or put the resistor in and don't worry about it)
I can tell you right now, if you are feeding that coil a full 12 volts, using 18 Ga. wire or larger, you have one HOT ignition!
---------------

That's a good reason to switch to MSD!!!
Tell your wife I said so!
MSD modules are the PERFECT Christmas gift!
Want me to e-mail her with gift ideas??

MSD A or MSD 6T modules... Always the right size, always the right color, and never returned!
The perfect holiday gift for those hard to buy for guys that don't know a damn thing about designer clothes!
(Think she'll go for it? [img]/wwwthreads_images/icons/wink.gif[/img] )




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