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Agentorange88
04-21-2009, 03:10 AM
What would be the cause for a dead short on the coil pack circuit? I am not able to find a wiring diagram that shows the circuit at all. Any help would be appreciated guys thanks.

KMT
04-21-2009, 11:28 AM
What year?

The coil is wired with direct 12v (batt) when key is on. Fuse #7 (as an example) in the PCB near the battery feeds it.

In some cases, the wiring at the PCB can become corroded and raise heck with things...need to pull it loose and inspect underneath.

I would start by pulling the power connector at the coil and seeing if that stops the blown fuse issue - if it does, you know the coil has shorted internally (to ground) and needs to be replaced. If it doesn't, start inspecting the harness leading off the coil - generally goes over the top of the engine front (check for belt cuts), towards the passenger side, then back center of the block to the harness connectors into the firewall on the pass. side as I recall. Not sure if all years similar, sorry.

Agentorange88
04-21-2009, 12:42 PM
It's a 91 SC. It seems that there is a dead short around the DIS module. I took it off to get it tested and had the battery connected and it was arching as I took it off. But I am not able to find anything that looks like it is grounding directly to the frame or body. As soon as you turn the key on it pops the 30A fuse under the hood. This car is cursed :rolleyes:

KMT
04-21-2009, 01:39 PM
Check the ignition switch. Pull the plastic bezels between the steering wheel and dash, then look down on the right side of the steering column - see if the switch is coming apart.

Agentorange88
04-21-2009, 01:49 PM
I'll give it a shot but I the switch was just changed a year ago so hopefully thats no the problem.

KMT
04-21-2009, 06:00 PM
If the fuse still blows with the connector off the coil and the ign. switch is ok, then my suspect would be a cut/munged/burnt harness.

Start disconnecting some of the related connectors inside the engine compartment until the fuse stops committing suicide. I'd pull the connector at the coil first, then the main harness connector back by the firewall. Then the sensor connectors/components that are part of that same circuit (cam sensor & crank sensor & DIS connectors). Don't forget to inspect underneath the PCB for burnt connections as well.

Dose the car have an aftermarket alarm?

Agentorange88
04-21-2009, 06:16 PM
No aftermarket alarm. I replaced the engine all went well tried to plug it all back in no start. Turns out I blew the coil fuse. I can't figure out where all the spade terminals go because all of the surroundings fell of at once. So I have two bare wire spade terminals. I blue one that comes out of the harness, a yellow one that comes out of the crank sensor, a red/green thats hot with the key on, a black one that comes off the coil and I think thats it. I left all of them disconnected and plugged the coil in blew the fuse in a few seconds. wires going to the coil got nice and hot. This is with the key in the ON position.

KMT
04-21-2009, 09:14 PM
>blew the fuse in a few seconds. wires going to the coil got nice and hot.

If you pull the wire/connector at the coil, and turn the key on, does the fuse blow?

Agentorange88
04-21-2009, 10:10 PM
No but its a brand new coil

KMT
04-21-2009, 10:27 PM
No but its a brand new coil

If you connect the harness to the coil without the coil mounted to/touching the engine/car, does the fuse blow?

If you make the harness connection at the coil and unplug both connectors at the DIS does the fuse blow?

I think you said something about someone grounding the DIS...how was that done?

Agentorange88
04-21-2009, 11:37 PM
Well I was removing the DIS at one point with the battery connected and both connectors disconnected and as I was turning the screws it was arching.

KMT
04-22-2009, 12:15 AM
Well I was removing the DIS at one point with the battery connected and both connectors disconnected and as I was turning the screws it was arching.

No power/connections to the DIS and you're seeing arching? Are you sure there aren't any wires trapped/snagged between the DIS and the mount?

Don't know what to say about a condition like that, sorry. Basically - it isn't possible...but not being able to look over your shoulder, anything's possible :)

What did you do? Did you replace and the sparks stopped? Can you take some photos?

Agentorange88
04-22-2009, 12:27 AM
Yeah I'll take some photos when I get off work tomorrow. I have no clue why the screw was arching and it hasn't done it since. Thinking maybe something was loose and came in contact with the accessory bracket and me moving the DIS made it arc. I'll try what you said about taking the coil off and seeing it its still shorting. Im pretty puzzled. The harness looks fine aside from a few wires I had to repair because they were broken internally. After the repair its still shorting somewhere. If anyone has an EVTM for a 91 I could really use a copy of the wiring diagram :confused:

KMT
04-22-2009, 02:34 AM
Maybe this will help...

Agentorange88
04-22-2009, 03:42 PM
That looks a million times better than my chiltons or haynes thank you!

Agentorange88
04-28-2009, 09:39 PM
So basically to break it down. If I plug the ignition components in one at a time I should find my problem. Well everything goes great untill you plug in the right side (gray connector) of the DIS module. At that point the wires going to the coil get hot and it pops the fuse. Only thing I can think of is the red/green stripe is grounding somewhere right? I've tested for resistance with the key off and its going dead to ground on the incoming side of the fuse. If I check for continuity from red/ lt green to ground from the outgoing side of the fuse its good. Now if I turn the key on I see 12V at the incoming side of the fuse but nothing is smoking so how is that possible? a relay maybe? :confused:
Thanks guys.

KMT
04-28-2009, 10:27 PM
>If I check for continuity from red/ lt green to ground from the outgoing side of the fuse its good.

Good as in nothing, zero zip (open) or good as in got continuity (closed)?

Is there no short when the right side connector is plugged in and the left side connector is unplugged?

Do you have one of those DIS where you can pop the lid off an see all the electronics sitting in gel?

Do you have a spare DIS?

Where is the harness section that connects the two connectors at the DIS? Front of the DIS and clear?

Any photos yet?

Agentorange88
04-28-2009, 11:59 PM
Good as in nothing, zero zip (open) or good as in got continuity (closed)?

-Going from the red/ light green leaving the fuse box it shows no continuity to ground. So that tells me the wire isnt shorted after the fuse box. Unless for some reason that wire is supposed to go to ground with the key off.

Is there no short when the right side connector is plugged in and the left side connector is unplugged?

-Yes I can have one or the other off and it be fine.

Do you have one of those DIS where you can pop the lid off an see all the electronics sitting in gel?

- It's an OE replacement from autozone. I just took it up there to get it retested and it was good.

Do you have a spare DIS?

- only DIS I have is my Motorcraft one which is dead.

Where is the harness section that connects the two connectors at the DIS? Front of the DIS and clear?

-It's almost out of the car to make sure its not grounding against anything. No knicks in the wires nothing bare. I might buy another one just to be absolutely certain.

Any photos yet?
- I have tomorrow off so I will try to snap a few shots tomorrow and post them up

Agentorange88
04-29-2009, 04:24 PM
So if I pull the DIS module off hold it it doesn't blow the fuse.. Any thought on that?

KMT
04-29-2009, 05:36 PM
So if I pull the DIS module off hold it it doesn't blow the fuse.. Any thought on that?

That was my next question. Can only figure it means a DIS internal short bridging to ground via the baseplate.

Ignition ground is pin 7 and internal is the right front connection to the baseplate.

Try to pop out the top cover section.

Agentorange88
04-29-2009, 09:43 PM
Well I finally got her to fire. Most of the problem was my ignorance. Seems like shes having a problem idling, Pretty good misfire throwing a code and ontop of that there is no tach. So going to try replacing the crank sensor and see if that clears it up any. I really appreciate your help.