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  • need a SIMPLE answer for a TFI question

    I've searched here, there, and everywhere. I can't seem to find an answer to what I'm asking. I'm doing the TFI upgrade on my '90 this coming weekend. I plan to use the Echlin ICR22 resistor when I install my coil, because at buildyour4x4.com, they recommend it (so I don't burn up my stock module with 12 volts). That's all well and good (even though the Tech install on the IFSJA homepage says not to use one).
    MY QUESTION IS...
    Why can't I just use the 2 wires that the original canister coil is using to hookup my new TFI coil?
    According to buildyour4x4, I'm supposed to find a keyed power wire, etc.
    Hook up the TFI coil

    "You?ll need to find a power source that has 8-12 Volts when the vehicle is running and zero when the ignition is off. This will be the power source for the coil. In Ford?s original TFI setup, only 8 Volts are provided to the coil. However, there is some general consensus that the coil can safely handle a full (12 V) power supply. Your stock ignition module could very likely fail if you use the full 12 volts, so we recommend using only 8 volts. If you want to run it with the lower voltage like Ford did, then you would simply put a resistor wire (see the part numbers chart above) in between the coil and the (+) power source. We chose to run the full 12 Volts directly to the coil for maximum power output. This resulted in our stock (OEM) coil becoming uncomfortably hot, and we ended up swapping out our ignition module with a prototype for the Mutant ignition module that can run on the full 12 volts. We recommend either upgrading your ignition module, or using the resistor wire to reduce the voltage. You?ll want to study the wiring diagrams posted below until you are comfortable that you have found the correct wires to splice into before you hook up your system. Once you have found the switched power source, splice it into the red wire on the TFI coil plug connector. Splice one of the green wires on the TFI coil plug connector to the green wire that comes out of the ignition module. The other green wire is not required, and can be cut off, or it can be left for future use in wiring up a tachometer."

    PLEASE keep the answer fairly simple, as I don't do so well comprehending what I can't "see". TIA

  • #2
    I have run both and no problem. No power differnece either way that i can feel. Another option is to lose the factory IM and replace it with a GM HEI. Did this on my 91 and will do it to my other trucks. 18 bucks for the module and about twenty minutes to install.
    Jeeps are Jeeps, keep Jeepin
    >It's not about the ten hour drive to get the rust bucket jeep, it's about where your your going when it's done
    87GW 99 Durango 5.2 drivetrain, SOA 35in Falken Wildpeak. MT rims
    1997 Ram 1500 5.2 33in Falken Rocky Mounts for haulin

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    • #3
      You can use the wires from the horseshoe connector with no problem, in fact it's the easiest way to hook up the new coil.

      Using 12V will give you a little boost in the spark, but it's not necessary.
      Jeep Grounds
      RRV Homepage
      Texas Full Size Jeep Association
      1987 Grand Wagoneer
      AMC 360/TF727/NP229
      1999 Wrangler Sport
      4.0L/AX-15/NV231


      ?Freedom is never more than one generation away from extinction? by Ronald Reagan.


      Formerly of DFW/Gun Barrel City, TX - eventually to return...

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      • #4
        Looking at the wiring diagrams, the wire that feeds the coil on the horseshoe connector is a resistor wire. It would appear that if you use the factory wire, the voltage to the coil will not be 12V.

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        • #5
          That's why I said using 12V will give a little boost, but is not necessary.
          Jeep Grounds
          RRV Homepage
          Texas Full Size Jeep Association
          1987 Grand Wagoneer
          AMC 360/TF727/NP229
          1999 Wrangler Sport
          4.0L/AX-15/NV231


          ?Freedom is never more than one generation away from extinction? by Ronald Reagan.


          Formerly of DFW/Gun Barrel City, TX - eventually to return...

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          • #6
            I used the factory coil wire on my TFI and it works just fine.

            Sure, the coil can handle 12v but over the years here, I've read plenty about the ignition module frying with 12v. As I said, I used the factory wiring and now 4 years later, its still working great.
            N4ZYV

            I ain't giving up. I've worked hard, it took me years to work my way to the bottom.


            1998 Cherokee Sport (not maroon! Have history with maroon XJs)
            1937 Chevy pickup (in progress)
            1966 Mustang
            1937 IH D2

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            • #7
              so the general concensus is that it is OK to use the factory 2 coil wires...along with the resistor that I will be putting in there

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              • #8
                Originally posted by bowtieman55
                so the general concensus is that it is OK to use the factory 2 coil wires...along with the resistor that I will be putting in there
                This is why I posted the cmment I did - I didn't think it was clear.

                The factory coil wire IS a resistor - you should not need an additional resistor. If you want to drop the voltge from the full 12V, then just hook it up with the factory wire, no need to add anything else.

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                • #9
                  ugg...where is Jode when I need him

                  I went to NAPA this morning, to pick up the ICC1 coil-plug wire and the ICR22 resistor unit that buildyour4x4.com specified.
                  "Your stock ignition module could very likely fail if you use the full 12 volts, so we recommend using only 8 volts. If you want to run it with the lower voltage like Ford did, then you would simply put a resistor wire (see the part numbers chart above) in between the coil and the (+) power source."
                  The resistor wire is over 4 foot long and has a male terminal on each end. Now I have no idea how to wire it in...or if I even need it. I don't want to take a chance on burning up my stock ignition module.
                  I'M DEFINITELY ABOUT TO PULL THE REST OF MY HAIR OUT.
                  Last edited by bowtieman55; 12-27-2006, 10:55 AM.

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                  • #10
                    I hooked mine up with the factory wire and took that resistor off that was on the old coil and the ICC1 connector and have had no problems
                    89 Waggy
                    Bjs 6" lift. 2" body
                    37" Trxus M/T
                    360/727/sadly a 229 for now

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                    • #11
                      I'm not sure why you'd want less than 12V going to the module. I've never heard of anyone burning up a module that way. I'm thinking "Your stock ignition module could very likely fail if you use the full 12 volts, so we recommend using only 8 volts. If you want to run it with the lower voltage like Ford did, then you would simply put a resistor wire (see the part numbers chart above) in between the coil and the (+) power source." may have a typo in it. Replace the word "module" with the word "coil" and it makes perfect sense. The last part of the sentence says to put the resistor between the coil and power source which would have no effect on voltage to your module.
                      Last edited by aerocorey; 12-27-2006, 11:08 AM.
                      Corey

                      Current
                      87 GW "Big Bear"
                      76 J20 project "Ox"
                      90 GW parts rig "Velma"
                      77 J10 parts rig "NoMo" (as in "no more Jeeps, Corey!")
                      94 YJ "Coop"

                      Past
                      88 GW "Hercules" (had to sell in '08, curious who has it now)
                      83 Wag parts rig "Shaggy" (used to build Herc, then scrapped)
                      73 J4000 (had to sell due to PCS in '07)
                      75 Cherokee "Jerry Lee" (sold in '13 because I'm an idiot)
                      74 Cherokee "Dino" (used to build Jerry Lee, then scrapped)

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                      • #12
                        Yeah, ditto - is it the coil or the module you're worried about? I thought the issue is one of burning up the module by running the COIL at 12V, because the module has to switch the coil current with a transistor inside, and if the coil is running at a higher voltage, it puts more stress on module.
                        Last edited by GWChris; 12-27-2006, 12:04 PM.

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                        • #13
                          Use the factory coil wire, it is a resistor wire, and you will get about 8 to 9 volts at the coil. Using a straight wire with 12 volts WILL make your Duraspark module so hot the the plastic sealant will melt and run all over your fender and the module will fry shortly after that. You don't have to ask me how I know, I've made that mistake. If you want 12 volts to the coil, either do the HEI module thing, there's a write on that, or get an MSD 6a box. I'm running with the factory wire and a Duraspark box and mine is fine. I am using the MSD TFI blaster coil, and I have a very hot spark.
                          GP
                          American Jobs should be for Americans.
                          Some Cheros run at 75, and some do 69,
                          But if I can get mine to start and run at all, I think I'm doing fine.

                          Big Mike
                          "Whoopi" 80 Cherokee Golden Hawk. 360/727/208
                          Horseshoe Bay, Texas

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                          • #14
                            I certainly appreciate EVERYONES input, but GP, you just took alot of stress off my shoulders. It sounds as though we are gonna have the same setup. I'm using the MSD #8227 TFI coil, MSD #8414 Cap-A-Dapt, and MSD #35859 8.5mm plug wires...whew, I've actually gotten a headache from this and I haven't even started the upgrade yet

                            edit-so I guess I can return the ICR22 resistor wire unit to NAPA now?
                            Last edited by bowtieman55; 12-27-2006, 12:59 PM.

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                            • #15
                              Originally posted by GWChris
                              Yeah, ditto - is it the coil or the module you're worried about? I thought the issue is one of burning up the module by running the COIL at 12V, because the module has to switch the coil current with a transistor inside, and if the coil is running at a higher voltage, it puts more stress on module.
                              Chris, I've been concerned with the possibility of burning up the module. APPARENTLY, the factory wiring IS a resistor wire...so there should be no worries...I hope

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