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Discussion Starter #1 (Edited)
I need some help with wiring. Yes, I am pathetic o_O I am hoping to get this figured out with some help from y'all. Here's a list of components.

I am running a stroked 302, with starter relay and battery relocated in the trunk. The IGN. Stwitch on starter relay doesn't need to be connected because of internal regulation on ALT??? Is this correct. I really want to finish up the wiring, but I don't want to make mistakes. Here some pics:
742221
742222



My confusion keeps circling back to the starter relay and one wire alternator. Will this diagram I made work? I am pretty sure I've made some mistakes in this diagram. Any help is much appreciated, thank you!
 

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Do not jumper the terminals on a Ford PMGR starter. It can cause starter run on after the key is returned to the run position, and can also back feed current into the electrical system. It doesn't matter if it is a one wire, connect the alt output to the starter solenoid large terminal along with all the other wires that require 12+. If you don't need the "I" terminal on the starter solenoid, use a Ford Motorcraft solenoid for a EFI Mustang. It is supposed to have an internal diode to prevent any back feed. Here's a drawing from MAD Elecrical on how to wire in a remote battery with the solenoid in the rear. You will need a Bosch type relay that can handle about 30amps or more to make this work. Note this scheme requires a hot alternator wire and a seperate dedicated start cable.
 

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Discussion Starter #3
I appreciate the info and Thank you for the diagram. Is there a way to do this without a relay? I am running fresh wire as I don’t believe the old wiring could handle amperage and it’s condition was less than satisfactory.
 

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The relay is there to prevent any back feed of current into the electrical system. You could probably wire it in without the relay but you will run the risk of starter run on. The guy that owns MAD Electrical is an electrical engineer and likes relays. He has developed several diagrams using relays to power various circuits and I trust his judgement. Another plus for the relay is that it removes the high current load from the ignition switch, which will increase its life and help to prevent failure.
 

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Discussion Starter #5
John, Thank you again for the great reply. I ordered a Bosch type 30 amp relay and wiring harness. The question I have is the "splice" is in the diagram. The "START WIRE" from original harness, I assume that is coming from the keyed ignition? Correct?
 

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Yes, you will have 3 wires spliced together, the start wire from the ignition switch, a wire from terminal 86 on the relay and the third wire from the starter solenoid small terminal.
 

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The relay is there to prevent any back feed of current into the electrical system. You could probably wire it in without the relay but you will run the risk of starter run on. The guy that owns MAD Electrical is an electrical engineer and likes relays. He has developed several diagrams using relays to power various circuits and I trust his judgement. Another plus for the relay is that it removes the high current load from the ignition switch, which will increase its life and help to prevent failure.
Is that the case with that type of starter or that the battery is remotely located?

Isn't the solenoid essentially a relay so I can understand the question about two relay in one circuit. It would make more sense to me if there were more components in that diagram.
 

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As you already have an early style starter solenoid with the 4 terminals, you can use the following diagram.
742400
 

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1966pw, you should also alter the wiring you posted.
Starting at the battery with the thick red lead that you have going to the ignition switch power +.
First, use a suitable sized cable to the alternator, no wire going between alternator and starter. The gauge you use will depend on length and amperage output of alternator.
Second you should have a large fuse or breaker mounted in the trunk protecting this cable.
All +12v power connections will connect to this cable via a fuse panel with suitable size fuses which goes to ignition switch power, lights, power hood, brake lights etc etc
For the starter circuit, you either need to follow the wiring diagram I posted (you would need to use the diode) or the one posted by J. Persons.
 

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Discussion Starter #10
Great, thank you BD. I like the figure F diagram and I think I will go this route.

Here's my updated diagram:

742447


Now for a couple follow up questions.

  • Any specific type or size of diode recommended?
  • Does the ignition pink wire and starter relay "I" with the diode need to be spliced together and connected to the ignition?
  • Do I even need the "I" wire with diode running to the coil with Sniper EFI. Couldn't I just connect pink wire "B" and be done?
  • Can I add a fuse to the alternator line before or after the distribution block? The alternator being used is 150amp, so a 150 amp fuse is correct size?
  • Will the distribution block work setup like this?

Thank you for the help :)
 

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"Any specific type or size of diode recommended? "
I am not sure what electrical shops you have near you since RadioShack's demise. You are supplying +12v via the diode to your Sniper ignition wire, this wire does not consume much power, the power for the coil, pump, injectors, etc will come from the constant power +12v lead going to the Sniper. A ~6A diode will give you plenty of reserve. Search on Google with starter solenoid diode and you will see different options depending on where you want to mount it. Putting a ring terminal on one lead and fix it directly on the starter solenoid would work well. Painless Wiring, Summit etc all sell them it does not specifically have to be a diode for this purpose use rated ~6A.

"Does the ignition pink wire and starter relay "I" with the diode need to be spliced together and connected to the ignition? "
If you are using a 1966 Ford Mustang style ignition switch, then you need to follow your diagram. The wire you have marked To Coil / Ignition coming out of the diode, connects to the "B - ignition" wire on the ignition switch.

"Do I even need the "I" wire with diode running to the coil with Sniper EFI. Couldn't I just connect pink wire "B" and be done?"
The existing wiring is designed around a points / coil ignition system. During starting with the starting motor running, powering the ignition coil, the voltage output can drop dramatically and not supply enough voltage to the ignition coil and hence to the spark plugs, for the engine to start. So what car manufacturers did was use an ignition coil designed to run at ~7v not the 12v as you would expect. So even if during a heavy load at startup, even though battery voltage may be as low as 7v at that time, it supplies the correct as designed voltage to the ignition coil. To protect the ignition coil after the engine has started and running, a ballast resistor is wired inline to the ignition so that it drops the voltage to the ignition coil to its designed / rated voltage ~7v. So on the original Mustang ignition switch generally, is not the same as a computer connected ignition switch. In the start position with a points / coil switch, the ignition or B terminal is disconnected with a connection made to the start solenoid. With a "computer controlled" ignition switch, generally in start the ignition or B terminal is not disconnected, the wire goes straight to the mini-style starter with solenoid on the starter motor. This is why you need to run that extra wire / add a diode which will maintain the +12v to your Sniper during start.

"Can I add a fuse to the alternator line before or after the distribution block? The alternator being used is 150amp, so a 150 amp fuse is correct size? "
If you are using a 150A alternator you should be okay with a 150A fuse but you might need to increase its size if added near the alternator. I would add just a fuse just after starter solenoid, mounted in the trunk. See the diagram J Persons posted and replace the 12 GA fuseable link with a fuse. Wired this way, you are protecting the complete wiring system from meltdown, a slightly higher risk when you have the battery in the trunk.

"Will the distribution block work setup like this?"
Yes, but I would add fuses as the wires come off the distribution block with a 150A fuse in the trunk area. In your diagram is drawn, any electrical issue would cause a complete meltdown of your wiring.
 

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You also need to check what size wire you are going to use for your thick red wire, you noted 8GA in your diagram, this might be too small with your amperage alternator. As amperage increases in a cable, heat is also given off. This heat is dissipated into the air but if the wire is installed under carpet, in box sections, this effect is reduced and the cable can get hotter than intended. You need to take into account a discharged battery with pretty much all the alternator charge going over the red wire to the battery.
Check out this guide.. Wire Size Calculator
Also I believe Holley require running the thick red and black wires direct to the battery. This wire should be sized accordingly with a fuse at the battery also.
 

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If that was my car, I'd just run the cable hot from the battery to the solenoid in the original location. It's just too much IMO. More to go wrong. Just run the cable safely and be done with it. The factories do.
 
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