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Discussion Starter · #1 ·
I just picked up a factory CJ tach, and Im trying to test it out on my FORD truck, it has the same duraspark ignition..

there are 2 red wires coming from teh tack with connectors, one male, the other female..

does any one know where this hook up in relation to the coil?

thanks


OzarkJeep
77 CJ5, in a bunch of sanded and primered pieces
 

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Well, I just hooked up an aftermarket one, and one of the wires goes to the negative post of the coil and the other was for lighting. Hope this helped. It might also be a power wire.

Keith

ITS GOOD ENOUGH /wwwthreads_images/icons/wink.gif
 

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/wwwthreads_images/icons/tongue.gif Hmmmm.......the factory diagram that I have shows a three-wire hookup....black is ground....yellow is ign power feeder.....and violet hooks to the duraspark violet wire. That shows clear up thru 1986. Are you sure that is a stock unit? 1974 and 1975 shows a yellow (+) feeder and a red wire to the ignition module. My book doesn't show a 76-'79 for some reason./wwwthreads_images/icons/frown.gif

CJDave
Quadra-Trac modified by the crack moonguy/wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/smile.gif/wwwthreads_images/icons/tongue.gif transfer case team.
 

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This is a 1983 era tach.
The red wires(one has a red stripe) are a loop that goes to the coil and (I believe) through the ingition module.
This is an old question on this board and an adequite answer has never been posted. The wireing diagrams are vague as to where the red wire goes after it leaves the coil and how the ingniton module handles the pulses made by the coil.

The last time this question was posed, Larry Van Every gave it a crack.
Here is his take on it if this will help though this particular application may not corrispond to the two-red-wire syle tach as there are several other wiring schemes both prior and after this one.
Needless to say, you chose a very difficult style to try to convert to your system.
On the bright side, There are plenty of CJ folks that would love to have this two wire unit, probably bad enough that they would pay you the price of a new, universally comptatble AutoMeter.
Just post it in the For Sale section of Off-Road classifieds an you will see what I mean.
=-------------- cut
Posted by LEVE
Posted on Wed Nov 3 22:53:55 1999

Well, if no one else will tackle this problem I will give it a try. I just installed a GM HEI two weeks ago with my Howell EFI System.... and it seems to be working fine. So, let's look at the TAC…

A TAC is driven by current. The current is supplied by the pulse from the ignition module. The ignition module differs in VOLTAGE levels from manufacture to manufacture, however the job the module does is the same. In fact, in a pinch, if you know all the connections of each of the OME modules, GM, FOMOCO, and DODGE, you could make up a set of swap connectors and connect a GM ignition module into a FOMOCO system and vice-versa. Things will work just fine.

Now the rub….if the pulse produced by the module is insufficient in width, duration or amplitude, the TAC may not work…

If you want to make sure the OEM TAC works with the GM HEI distributor, run the two modules in parallel. Here's what I mean….

Leave the OEM FOMOCO ignition module in place, connected to the harness, but with the FOMOCO Coil out of the circuit..

Now run a spade lug/wire connector from the GM HEI TAC connector down to the COIL TAC pigtail and connect the two together. Start the Jeep, the OEM TAC work.

Now turn off the Jeep and then unplug the OEM FOMOCO ignition module…

I'd bet the tack will still work… however unless you did the Nutter Bypass, the OEM Computer will be brain dead!

Let me know how it works.

Larry

Good Jeepin'

Larry

JAF
http://www.monsterslayer.com/jeep
 

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Discussion Starter · #5 ·
great...typical, I buy soemthing I dont really need, just WANT and get into a big mess with it...

Id rather just sell it and get a different one, but is ther ANY way to test it>
I dont want to sell a bad part?

thanks for all of the input!


OzarkJeep
77 CJ5, in a bunch of sanded and primered pieces
 
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????? this cjd post puzzles me......... We have two CJ-era jeeps, one 83, and one 85...... And, neither of them have any black, yellow, or violet wires. They are both of the 'two-red-wire' variety, as mentioned in the other posts. And, neither of our tachs work, still connected to stock systems. One is intermittent, coming on maybe 4 or 5 times per year.

bobH
 

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/wwwthreads_images/icons/tongue.gif Hmmm....we can't Jeep-verify that BBKNS. We have never had a tach for the CJ, and none of our friends do either, so we are strictly slaves to the Haynes manual here/wwwthreads_images/icons/crazy.gif

CJDave
Quadra-Trac modified by the crack moonguy/wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/smile.gif/wwwthreads_images/icons/tongue.gif transfer case team.
 
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I shudda mentioned in the 'other' post..... I was just on the phone with the MSD tech support folks. And, I had a tach question for them. And, the question had nothing to do with using MSD products.... it was just 'how do you trigger a certain tach, to a certain ignition. And, the person that I spoke with was very helpful. You might try MSD tech support at 915-857-5200. Based on the info that was said to me, I believe the CJ (83-86) tach is a 'current-triggered' tach, and if you hook it up 'in-line' (in-series) with the wire that feeds from the ignition switch to the DS module, or DS coil-plus, it should probably 'trigger'. I'm not sure which of these two feeds, but I'd probably try both of them. Having looked at the wiring that feeds the ignition in one of my CJ's (an 83, 6-cyl), I would speculate that there is a wire from the ign switch to the tach, then the other side of the tach seems to feed through the firewall, and then it splits, with one lead taking 12v to the D/S module, and the second lead being a resistor wire that feeds the coil. I am not real sure about any of this - I've never looked real close.

bobH
 

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Discussion Starter · #9 ·
ok, tonight I finally had time to mess with the tach in my FORD truck ( 300 inline 6 cyl, duraspark)

one wire to the red coil wire, and the other wire to the battery produced the correct RPM reading on the tach.

sorry i dont remember which red wire on teh tach was which, its really simple, i just uesed the test leads from a VOM..

thanks for the help earlier guys!, maybe somebody somewhere can benifit from this



OzarkJeep
77 CJ5, in a bunch of sanded and primered pieces
 
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