I did a DS2 swap on my 300-6 Bronc and have had no problems till now. I have zero spark. All ignition components were new then, and have all been tested since it quit. Harness has been completely checked out for continuity, I've rebuilt the harness like 6 times now, checking every wire and plug. If everything is unplugged from the harness (mine) except for the pick up coil plug and the fat red wire that powers the + side of the coil, (the other three are disconnected in that plug) I get ground on the green wire, the black wire and the fat red wire. Basically my problem is that the fat red coil wire causes a ground condition in the key off position. I have fried 3 ICM boxes in 2 days. I cannot figure out how or why that fat red coil supply wire is hot if the key is on and ground if the key is off- that just flat makes zero sense to me. Help Please!

 

You are getting backfeed through the coil. If there is NOTHING else connected to the coil but the red wire that is supposed to be positive, you have a grounding condition at the coil or somewhere in the red wire between the coil and the keyswitch/relay. Make absolutely certain there is no continuity to ground through the coil before you test.

However, if the ground wire is connected to the coil when you test in the key off position, it WILL read ground through the coil in the red positive wire. At least if this is what is happening you can rest assured the coil is good.

 

We are testing everything with nothing hooked up. NO wires to the coil whatsoever. The only reason I brought that up was to show how we found out the ground condition (key off) on the coil hot side wire coming from the truck harness.

We now have the entire dash out of the truck and the wiring harness strung out and unwrapped. The problem is from the plugs back into the main truck harness. EVERYTHING from that point out has been tested. Somehow we have gotten rid of the "ground with key off scenario" for the fat red wire/grn stripe (coil wire). Now we have the same scenario with the red/blue stripe start wire (two wire plug to the icm, a red wire and a white wire) when the key is off, and have fried yet another box. How can a wire be a ground when the key is off and a power wire when the key is on?

Coil- tested out good.
Pick up coil- tested out good.
DS2 harness- tested out good.
ICM tests good, until you plug it in, then it fries itself.

The problem is from the plugs back into the firewall, in the main harness. I believe the ballast resistor to be good as the test light shows dim when touched to the coil + wire in the run position, bright if only on the start side. According to the diagrams I am using, that makes sense. But how am I getting these grounds? I believe the wire we're getting it from now goes to the neutral safety switch. But if that were to ground out, we would have a no crank scenario, as it has not been bypassed. Correct?

 

Assuming you have a dead short, yes. If the problem has been traced to the NSS then disconnect at the switch and see if the grounding issue is still there. If so, you have narrowed it to a point between the neutral safety and the harness connector. I would check beyond the neutral safety anyway just in case the problem goes away once its disconnected but exists in the harness BEYOND the NSS connection. You would have to check this at the NSS connector since the switch merely breaks the line as it passes by.

 

If memory serves me right (It's been a long day) the ground scenario is there on the NSS wire when we push the button, or engage the clutch, an open condition when it is not.

 

That would lead me to believe the condition is further back in the harness than the switch since it merely breaks the connection when the clutch is NOT engaged.

 

Yes sir, that is kinda what we were thinking. We were hoping someone else had been through this, and could tell us where they found the problem. My Bronc looks like a bomb went off inside, wires everywhere. I guess it sounds like we are on the right track, I'll keep tracing wires I guess. Thanks for your help!

 

Electrical issues are always a nightmare. I feel your pain. I replaced two starters and three batteries once before I realized the positive battery cable had corroded so badly from the INSIDE out that when I metered it, it read battery voltage however, it showed several HUNDRED ohm's resistance when I finally did a continuity test on the cable itself. When I got this reading I pulled the cable and split it open length-wise. Nothing but copper oxide down the middle with maybe two or three strands of wire being continuous through the length of the cable. And that's just one story.

Best of luck. If you get stuck, you can try disconnecting the NEG battery cable and doing a continuity test on the wires that are suspect. That way you can concentrate on resistance within the harness which could be part of the problem.

 

I have been doing continuity tests, but never thought to disconnect the neg cable. Hoping to get to work on it some more tomorrow since they are calling for rain here. (I work construction)