Is anyone running a full 12 volts on there TFI coil?

[JeepFreak]

Just wondering if the TFI coil was designed to run on a full 12 volts or not? If so I will make mine run on 12.

[liliysdad]

acording to the team rush page, the text says full 12 volts, but i think the diagram shows 9.6(?) i am wiring mine right now, and will run a full 12 to it. the coil seems to be the same design as the coil in an hei chevy, and these require a full 12, so i am going to be a guinea pig. i guess that is the benefit of buying a coil with a warranty from autozone. how you doing rick?? hadn't talked to you in a while.

[JeepFreak]

Well dang you are alive! Hows the truck coming. Must be hard packing and working and trying to wrench on the truck. So everything all bolted up and ready to run? I finally got rid of that white Wag and have almost got my garage all cleaned up! Been a little warm to work to hard though. We need to hook up sometime when you get the truck running. Oh and the wife wrecked the Suburban but may have already told you that.

[shadowfax101]

I am runing mine with 9.6. I thought it was suposed to be 12, but after I wired it into the harness I only get 9.6. It is because of the ignition mod. When I unplug it I get 12 to the coil. When it is plug in it drops. It must be a built in resistor

[liliysdad]

does the module supply 12 volts at crank, but 9.6 when running?? seems i heard this somewhere?

[Oracle]

Hiyas Freak smile.gif hey, when you guys decide the answer to the 9.6 vs 12 will you post it? I've got 2 GW's I'm going to TFI upgrade. Thankx

[liliysdad]

when i hei'd my 258, i ran a direct 12 off of the starter solenoid. how does the module "suck"2.4 volts ou of the coil. if you run 12 to it, it should have 12. am i missing something??

[JeepFreak]

I deleted my other post and am looking at the wiring before I answer.

[trssho]

I have the Ford cap upgrade, but am running an Accel coil. I ran battery voltage to the coil...I by passed the built in resistor in the circuit. Been 4 years between my 2 Wagoneers, and have had no problems.

[ June 26, 2002, 04:36 PM: Message edited by: trssho ]

[mtn goat]

This is how I understood it after lots of research (although I was just reading others opinions) The coil can handle the 12 volts just fine, and does so at start up conditions. The problem is the ignition module in our rigs. supposably it can not handle that kind of output all the time so a resister wire is stock running from the module to the dizzy.

[chrism]

The Ford TFI coil is designed for 12 volts. It will run with 9.6 but you are not getting the full spark energy the coil can put out.
I just converted mine, but used the original coil wires. Does anyone know exactly where the resistor wire is? I would like to bypass it.

[Langdon]

Have been running mine at battery voltage with MSD 6A for 2 years with no problems. :cool:

Just follow the + wire from the coil, you will see where the resistor wire ends... smile.gif

[J20fan]

I just went and checked mine, I am feeding it 11.8 volts I have 12.4 at the battery. When I check the voltage at idle it is 9.6-7 at 2000 RPM it is 11.8.
shadowfax101 mine reads 11.8 until I plug the coil in then it drops to 4.5 - 4.9. I am taking the reading with the -12 at the battery, perhaps it should be at the module?

[Joe's 89]

I asked the same questions and wonered the same thing after seeing those same posts.

I just cut the wires, stuck the new coil in, and it's been almost three months with the better idle and faster starts.

I think there is a built in resistor on the later models, although I couldn't tell you WHEN they started doing it.

Joe

[PAJEEPER]

Yes there is a built in resistor wire in all '78 and up FSJ's. All Jeep and Ford Duraspark systems have it. I beleive it evens out the current going to the coil to avoid voltage spikes. When running the alt puts out like 14 volts or so, the TFI coil only needs 12 so this is where the resistor comes in. It is bypassed at startup by a wire off the starter relay for quiker cranking.

So if your FSJ alredy had the motorcraft system dont worry about the resistor. If it had another ignition then add a resistance wire or a ballast resistor. And for it to receive full voltage at startup you need a starter relay with 2 of the small terminals on top. Ones for the relay other is for the resistor bypasss. And I dont remember what they are labeled as but its not tricky at all to wire this up.