What is the black wire running to negative battery terminal?

[cbccadet2002]

So i've been busting my head on my gals son's grand marq. Its an 86 with the 302. He was on his way over to her house and out of nowhere the car dies. When we arrive we attempt to start it and nothing. We get it towed home. After about 20 mins or so, i turn the key and it fires right up. Figured damn, maybe just a nut buster for the time and good to go now. Nope, after a minute or so it dies again. So i'm thinking its a fuel related issue. I go get 2 gallons of fuel, pour it in and try again. It does the same thing. I proceed to check the connections on the 3 relays. I clean them all up. Check the inertia switch, double check and pump is priming. Schrader valve shoots fuel while cranking. Well anyway, now there isn't any spark after the coil freshly installed. I am wondering what the black wire with plug that is directly attached to the negative terminal is exactly. I broke the clip while attempting to take apart and clean it after i freshened up its connection to the terminal. I'm going to pull the tfi off tomorrow and check resistance to hopefully discover thats what needs replacing. Going to go ahead and change out the fuel filter also, since i'm sure it could use it. I've been reading a bunch on the net, but Everything seemed to go downhill after i attached that black wire to the battery again. Also pulled the coil wife from the cap and the nipple came out with the wire. Is that acceptable? I've never witnessed this before. Do you guys have any other suggestions of things i could check? Any and all ideas are greatly appreciated, I wish i woulda went to school for automotive instead of machine shop during times like this lol. Thanks in advance.

[L1011tristar17]

When my car used to randomly die and not want to start up, it ended up being a bad TFI module.

[L1011tristar17]

It also may be worth a shot to check the condition of the ignition switch. You'll find it in the steering column under the plastic shrouds. If you can see that it's splitting apart, it's time for a new one.

[gadget73]

The black wire to the ground terminal is the ECM ground. It needs to be connected or the ECM may not work properly.

[cbccadet2002]

would this ecm ground cut spark to the coil? I do have 12v to coil with the key in the run position. I haven't got to check it while cranking. I'm going to check the voltage at the pip wire on the tfi both in free state (run position) and cranking. I found a video on utube stating it should be 4-5v during cranking. Seem about right? I went ahead and had her get a tfi module. Gonna grind down a 5.5mm socket to remove the mounting screws and toss it in. I'll also check the ignition switch. I've been trying to come across a haynes manual but the local parts store doesnt have one in stock. Sucks when trying to locate where things are. Thanks for the input. Greatly appreciated.

[Piece-it pete]

Howdy cb!

When the module died on my old 85 Town Car the coil was getting power in run but not start.

Pete

[cbccadet2002]

im not getting any spark from the coil. it has 12v and both the connections. The red is the constant i take it, and the white/blue and cant remember the other color is the switched? The white/blue combo drops voltage on cranking so i take it thats the switched circuit. Where is the engine ground located on these blocks? This one is so saturated in oil is horrible, cant see anything under there lol. Guess i gotta fix that next. Its a brand new coil, it should fire. Unless its faulty.

[cbccadet2002]

Im having a hell of a time trying to use the search for this forum's server. Just me?

[cbccadet2002]

nvm found the engine ground. looks legit. guess after battery charges ill throw the new tfi in. Was trying to troubleshoot and confirm it was the tfi that was bad before i put it on.

[cbccadet2002]

tfi problem solved. It has a slip in the idle, i think i might have cracked one of the clips on the fuel pump relay. I tapped em all together to hold everything tight for now. Any idea where one can locate replacement connectors? On a side note ford couldn't have made the tfi replacement anymore of a tight squeeze huh? lol thanks again

[sly]

TFI replacement usually requires lifting the distributor out a bit for clearance.

[Mainemantom]

My 83 GM is doing the same thing. Four "mechanics" and no one can find the problem. I will replace the TFI again.

[cbccadet2002]

ya i was iffy on picking it up outta the intake, wasnt sure what was underneath. still gonna peep out that ignition switch for reference,

[cbccadet2002]

hey maine. have you checked ur pickup coil?

[gadget73]

My 83 GM is doing the same thing. Four "mechanics" and no one can find the problem. I will replace the TFI again.

That would be interesting, considering an 83 doesn't use a TFI module 83 should be EEC3 with a Duraspark box. Its driven off a crankshaft trigger, not a pickup in the distributor. Theres actually not really much of anything in the distributor, just a shaft and a rotor. Make sure the crank trigger is good and the connections are clean or it won't do anything.