wrong voltage at coil TFI

[bigchief79]

Let me try to get all this in for you electrical guys. (79 Chief 360) With the ignition ON you should have between 5.5 and 6.6 volts at the coil. I am getting 4.5v If I pull the two red and blue connected wires from the starting solenoid I have 4.5v on the red wire but If I disconnect both wires from the COIL I have 12v on the red wire. I have always had the correct voltage (5.5) but recently checked and the voltage is low. Did a TFI upgrade a while back. Would the different coil cause this low reading or another problem? Any TFI guys run into this and if so how do I fix it? Thanks

[Cecil14]

You are suppose to run a true 12v lead to the TFI coil if I'm not mistaken. It uses more power than a standard coil becuase it puts out more volts.

Anthony

[ July 19, 2003, 06:47 PM: Message edited by: Cecil14 ]

[AJ Johnson]

yeah.. most previous ignitions had a ballast resistor inline to drop the voltage before the coil.. Not 100% positive on the TFI system, but on the GM HEI system, you have to have 12 volts... i can't think why on the TFI it would be different than the GM HEI.
so.... just run a 12V line in there.

[timmirvin]

If you dare to enter "TFI" in the search engine you might find where we had a huge discussion earlier this year concerning voltage to a TFI coil.

Yes, the TFI will run just fine on 12V and the 4.5V you are getting sounds low.

But if I were you I would read all those long postings from this Spring. Believe me, you will learn more than you ever wanted to about coils and the TFI system!!!! smile.gif smile.gif

[bigchief79]

did a search on tfi but I didn't find the huge discussion. If I run a 12v wire to the coil, what would trigger the coil? doesn't it have to be hooked to the box?

[Cecil14]

There's a how-to around here somewhere but I believe you just find the normal lead to the coil and by-pass the ballast resistor so it always get's 12v.

This is for a 6 but the idea should be the same.

TFI upgrade (http://keith.cj8.tripod.com/tfi_upgrade.htm)

Good luck,
Anthony

[ July 20, 2003, 09:02 PM: Message edited by: Cecil14 ]

[JDJeep98]

So... what's the decision?
Will 12v shorten the life of the TFI? Should I remove/bypass the resistor wire or leave it alone? I'm still confused! :confused:

[AJ Johnson]

no, it won't shorten the life... just remove the resistor, or bypass the wire, and you should be set up properly

[Cecil14]

Originally posted by JDJeep98:
So... what's the decision?
Will 12v shorten the life of the TFI? Should I remove/bypass the resistor wire or leave it alone? I'm still confused! :confused: The TFI ignition is a high energy system, meaning it was designed to push more voltage to obtain a bigger spark. Running anything under 12v to it will only hinder it's performance.

Anthony

[JDJeep98]

OK, that sounds logical... :D
Where do I find the resistor on a '90 GW?
What's the best way to get around it? Bypass wire? Remove it and throw it away?
I'm still getting used to my 360 and don't know where everything is... :confused:
Thanks.

[Cecil14]

Try the link I gave ealier, TFI upgrade (http://keith.cj8.tripod.com/tfi_upgrade.htm), as I said it's based on an upgrade for a 6 but the ignitions should be the same other than the distributor.

Anthony