quick battery relocation question

[Jh8990]

Ive searched through old threads about relocating the battery and I read that it would be best to ground the ecu directly to the battery by tapping into it and running it directly bad with a dedicated ground wire for it to help with noise? but where do I find this ground at exactly. any pics? I read something about pin # 40 or 60 or something. would that be on the ECU harness behind the glove box?

Thanks for the help in advance.

 

[Jh8990]

anyone? I got off of work early this morning and I was planning on doing it today so it would be nice to be sent in the right direction.

 

[Off Road SHO]

There is no reason to have to go to all that trouble, the current set up is just fine. And you are correct, pins 20,40 and 60 (the last pin in each row) is black and is grounded. They connect to various points around the engine bay and act as collector wires for devices that also need to be grounded. The uni-body skin/frame makes for an excellent bussbar, that is why they do it that way.

For every 4' you add to the length of your battery cable, I would go up one guage size. I think the stock cable is a #4 so if you add 4' feet in length, use #2 cable. This is overkill, but I never liked having too much resistance in 12 volt systems.

I know you probably already know this, but you should run the positive cable in a non-mettalic conduit, from the battery's new residence to starter solenoid or wherever it connects to. You can then run a separate cable from that point (not in conduit) to the main power fuse box. Never put a mechanical connection between your battery and the device that sends the current to your starter, that should be a one-piece cable.

Tom

 

[Jh8990]

thank you for your help. and correct I will be doing that. I already have 1/0 gauge ran from the front to the back and then I will just need an extra cable going to the starter as stated before and then just to be 100% clear that is all it will take to start my car once everything is connected correct?

 

[gmorrell]

If you want to keep the EEC grounding as Ford intended it, and trust me, as an EEC designer, I can attest that Ford did all this for good reason, run 40 and 60 back to the battery negative with separate 12 gauge wires. 40 and 60 are EEC's high current ground dumps, and they want to return to a good, low impedance ground, and it doesn't get any better than the battery - terminal.

Running important grounds through the chassis is asking for trouble. The chassis is highly inductive, the ground paths change as the vehicle moves and flexes, and it all gets worse as the chassis ages, corrosion builds up, spot welds break, etc.

EEC pin 20 is called "case ground" and is a noise dump. Each of the signals on the EEC 60-pin has a resistor-capacitor noise filter which is meant to filter incoming noise and bypass it to ground before it gets to the EEC internals, but Ford did not bypass these noise filters into the power ground (pins 40 and 60), rather, they (smartly...) bypassed the noise filters into pin 20, which is meant to dump noise into the vehicle chassis local to EEC. Keep the wire from pin 20 short and tied to the chassis.

Edit: I'm not saying that what you're doing won't work, plenty have not followed these guidelines and been fine, but if/when EEC starts doing wacky/unpredictable things, grounding it as the designers intended will often fix the problems.

 

[Jh8990]

ok thank you so where exactly do I find these wires at? do I have to reach behind the glove box and tap into them there? and just so I get this straight (because I want to do it right the first time) I run pin 40 and 60 back to the negative terminal with their own dedicated wires, along with grounding pin 20 again to somewhere on the chassis? or should I run that wire back as well?

 

[gmorrell]

If you're not relocating EEC, pin 20 grounds to the chassis right near where EEC penetrates the firewall, no need to change pin 20.

40 and 60 run up to the front passenger fender by the battery, Black with a Green tracer IIRC. They combine together, go through a single pin connector, and lug to the chassis. Also lugged to the chassis on this same screw was a ground wire from battery negative terminal.

Cut off the connector, splice two new wires on the existing grounds and run them back to your relocated battery. With these wires, don't just use crimp splices, pull the metal crimp sleeve out of its insulation tube (you can drive the sleeve out of the tube with a drift punch), crimp it and solder it, then insulate.

 

[Jh8990]

ok sounds good. thanks for your help.

 

[SHOBlu]

^ good info Gary, but is it advisable to run pins 40 and 60 back to a trunk mounted battery? If so, what gauge wire should be used? I'd like to do this with my 95 ATX.

With my 94 ATX the battery is in the trunk already - passenger side, right behind the seat and up against the wheel well. I got the kit from Summit and it included the alum. box, 2g positive and negative wiring, and mounting hardware. I ran the positive to the (+) post on the alternator then a 4g from there to the starter. The negative runs to the strut tower. I've had no problems with any of the electrical in 4 years!

*edit- sorry for my redundent posting.

 

[Jh8990]

yeah I think I am going to do it the way gmorrell suggested since he obviously knows alot about what he is talking about. way I look at it, its worth to take the extra time to run those two separate wires to the back and ground them on the battery. better safe than sorry when it comes to SHO.

 

[SHOBlu]

Agreed.

 

[trainguy1989]

Could you run pins 40 and 60 to negative battey cable in the engine bay?

 

[SHOBlu]

Could you run pins 40 and 60 to negative battey cable in the engine bay?

According to what Gary said, you won't do any harm connecting them directly to the (-) post on the battery. Where the real benefit of connecting them to (-), is when the battery is mounted in the trunk.