major wiring, msd involved

[dastang2]

i gotta huge wiring problem. i have no power at the positive side of the coil but the negitive side is hot to the touch and so is the coil. i had the msd box hooked up to the battery for testing the motor. the wire that gives power to the coil when the key is on stopped working when i accidentally grounded it for a second. i could not find a blown fuse or fusable link. what i did was hooked the msd power wires to the battery and it ran. but i was wiring the box inside the car a few days ago and got it running after a while of messing with wires. today i was going to finish the job and i don't know what i did to make it run the other day. i have a switch on the small power wire of the box which is supposed to be on when the key is on. that is wired straight to the battery and so is the main power wire. i got the distributor hooked up just fine. the problem is getting power to the coil. if i hook power from the battery to the positive side of the coil, it melts the wire. but the coil is always hot to the touch now with the neg. wire. i tried another coil and still nothing.does anybody know what is wrong with the original wire that give power to the coil when the key is on. i checked the coil and i believe that i have the wires on correct and not crossed. this is a duraspark distributor and a carbed engine. with the msd do i just hook the coil wires from the box to the coil and leave the stock wires off of the coil.

 

[302RollinHard]

Heat emitted by electric wires usually means a short or severe resistance (read:bad ground, insufficiently sized wire, etc) I would check your grounds (battery to chasis, engine to chasis, etc) and make sure they are good and clean and then look at if you need to make them bigger (4 gauge)

 

[dastang2]

those are good, that was checked too. i am not getting power to the coil through the pos. wire, i think it's going through the neg. i think there is something i did under the dash that is sending power to the wrong end of the coil. i didn't see anything though. i just had it cranked a couple days ago.

 

[302RollinHard]

coil itself might be bad???

 

[dastang2]

i switched coils and still nothing

 

[HISSIN50]

When you ran battery power to the coil, had you disconnected the OEM wiring harness/connector from the coil? Otherwise, if there is a short in the OEM wire, it would have continuity to the battery.

IIRC, the key-on positive power for the coil comes from the EEC relay. Do the solenoids under the hood energize still?

That's a real mess. Good luck.

 

[jrichker]

Check out the ignition switch to coil wiring in the upper LH part of the diagram.

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

 

[dastang2]

do i unhook the stock coil wires from the coil and replace them with the msd wires right. i did unhook the positive wire from the coil and it still arcs.

 

[jrichker]

From MSD's website installation docs...

 

[dastang2]

ok i got it. i must have had a short or too much resistance because i moved the box back out to the battery and the car started