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EFI wiring Questions - 3 parts

3T

Full Member
Joined
May 24, 2006
Messages
167
I'm almost done with my engine swap and have a few wiring questions that have me stumped. I have a 93 5.0 Mustang motor and harness.

Part I - Grounds
According to some other threads, I need a ground from the intake manifold to the body (firewall) and another ground from the block to the frame. Is this correct? I am confused about the ground from the battery. Where does the ground go from the battery? There is a big wire and a small wire. It looks like the small wire goes to the body and grounds the computer. Is it necessary to grind away any paint to get to bare metal?

Part II - Relay & Fuses
Ryan's website lists the use of 4 relays: 1. EEC, 2. MA/O2, 3. Ignition, 4. Fuel Pump. First of all, I can't find anything that tells me what amp fuses to use with each relay in the new fuse block. So if someone can tell me what amp fuses they are using for each relay, that would be great. Secondly, according to Ford there are only 3 relays that was used in the Mustang harness: EEC, Fuel Pump, and A/C. Do I really need the MA/O2 and Ignition Relays?

Part III - Starter/Alternator/Relay & Solenoid/Coil Setup
I need help putting all these components together. I have both the Bronco's solenoid and the Mustang's solenoid. I am currently trying to use the Mustang one but if need to use the Bronco's - that's fine. The Mustang has two larger posts on the top and a single smaller one. I understand that the starter goes on one side and the alternator and + cable to battery goes on the other. Does it matter which side? And that is as far as I have gotten. Does the hot wire (light green and red) to the alternator go the ignition relay or straight to the ignition switch? Does it need a fuse? What do I do with the brown and red/green wire going into the Bronco's solenoid?

Hopefully, this is it and I'll be ready to crank her up!
 

ransil

Bronco Guru
Joined
Sep 6, 2003
Messages
8,122
Part 1 - Grounds
Engine ground should go from Battery - Block - Frame - body
Use a braid to the frame & body, the smaller wire can go to a grounding block.
see pic in this thread for the grounding blocks I use.
http://www.classicbroncos.com/forums/showthread.php?t=101731
don't use sheet metal screws to body panels you are only looking for problems.

Part II Relay & fuses
Start with 10 amp and go up if they blow.

Part III Starter/Alternator/Relay & Solenoid/Coil Setup
Only use the Mustang solenoid, does not matter which post.
I think you can leave out the brown it went to the ign box.
The red/green is what starts the engine goes to the s terminal of the solenoid.


disclaimer - this is from memory I looking at any diagrams at the moment.
 

00gyrhed

Bronco Guru
Joined
Aug 3, 2006
Messages
2,428
Add to ransil

Part I

Just ground everything to everything with as big a cable as you can. The systems needs a consitant ground everywhere to avoid false readings.

Part II

You only need the O2 relays if you aree running heater O2 sensors on a SD system but I think you need them on a MAF for burn off of the element.
 
OP
OP
3

3T

Full Member
Joined
May 24, 2006
Messages
167
Part I

OK let's see if I have it straight. You take the big negative wire from the battery and that goes to the engine block? Where?

Part III

What is the s terminal on the Mustand solenoid? Is it the smaller post? Then what do I do with the red/lt green wire from the 2G alternator? Does it go to the solenoid somehow or directly to ignition switch?
 

ransil

Bronco Guru
Joined
Sep 6, 2003
Messages
8,122
Part I

OK let's see if I have it straight. You take the big negative wire from the battery and that goes to the engine block? Where?

Find an empty and put a bolt in it or find a bolt with nothing connect to it. should be one behind the alternator somewhere. Do not use one with a bracket already attached.

Part III

What is the s terminal on the Mustand solenoid? Is it the smaller post? Then what do I do with the red/lt green wire from the 2G alternator? Does it go to the solenoid somehow or directly to ignition switch?

S= start that is what starts the motor.
RED/lt green - Find a run wire coming off the ing switch, it need =12 volts when the vehicle is running to turn on the alternator and make it charge the battery.
 
OP
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3

3T

Full Member
Joined
May 24, 2006
Messages
167
Oops I'm sorry, I didn't mean "what is the s terminal." I meant to type "where is the s terminal?" I'm guessing it is the smaller one????????
 

ransil

Bronco Guru
Joined
Sep 6, 2003
Messages
8,122
Oops I'm sorry, I didn't mean "what is the s terminal." I meant to type "where is the s terminal?" I'm guessing it is the smaller one????????

Yes it is the small one.
 
OP
OP
3

3T

Full Member
Joined
May 24, 2006
Messages
167
OK great thanks!

I just found the amps for each fuse for each relay on fordfuelinjection.com!! I guessed I missed that one.

Are there two different wires coming out of the ignition switch? One for START and one for RUN? Is the ignition wire coming out of the red plug near the throttle cable START or RUN? I think that one is RUN and the one that goes to the solenoid is START. Is that right? I'm curious how does RUN and START become hot?
 

ransil

Bronco Guru
Joined
Sep 6, 2003
Messages
8,122
OK great thanks!

I just found the amps for each fuse for each relay on fordfuelinjection.com!! I guessed I missed that one.

Are there two different wires coming out of the ignition switch? One for START and one for RUN? Is the ignition wire coming out of the red plug near the throttle cable START or RUN? I think that one is RUN and the one that goes to the solenoid is START. Is that right? I'm curious how does RUN and START become hot?

That would be too easy.

There are a few plus wires coming off the switch. You need a wiring diagram for your year of vehicle to identify them. Its online somewhere, search CB.com someone post the links not too long ago.
 
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