Wiring 302 into 3.0

l0sts0ul · Feb 7, 2015

Hey guys.

So I'm balls deep into this swap and I'm trying to figure out the wiring.

I put a carbed 302 into a 94 3.0. I have the EVTM for my truck but I'm having a heck of a time trying to understand some of it. ( I am an electrician so I can read schematics; but trying to follow the connected/cct/Pinot seems harder than it should be)

So I've built a customer instrument cluster and used the existing left and right signal wires from the original, as wel as the fuel gauge wire from the sender (in the fuel cell I installed), existing power and grounds as needed, and run the other wiribg aftermarket to my other new gauge sensors. This is where I start getting screwed up.

I kept as muh of the harness as I could, just cutting out what I thought was efi based wiring. But now it seems I've cut out my fuel pump relay, which I could rewire but in an effort to keep the inertia switch, I think I caused a problem. I would like to bypass the inertia switch now for ease of install, but not sure what wire on the the c105 (firewall pass through plug) to use to power the relay from the ignition switch

Now, all I want to keep on the cannon plug is the lighting, ignition controls, and whAtever else is required but that's it.

I need some hep here please, this is literally the last step for me before I start this sucker, break t in and do some finishing touches.

Thabks

RonD · Feb 7, 2015

Fuel pump relay did get 12v when key is on from the EEC relay, it would be closed(fuel pump on) by the computer by Grounding the relay.

There would only be 1 wire thru the firewall for the fuel pump, a Dark Green/yellow stripe wire, this would run to the inertia switc, from the fuel pump relay.

Power path for fuel pump power, not relay power
Battery----------30a fuse-------fuel pump relay--------inertia switch----------fuel pump

Engine bay has the battery, fuse and relay part of this circuit.

If you want to make the relay close when key is on, then just ground the relay, Light Blue/orange stripe wire that runs from relay to computer, assuming EEC relay is still being used.

If EEC relay is no longer working then get 12v from the Coil "+" terminal, Red/light green stripe wire

Battery--------60a fuse-------ignition switch--------Coil------fuel pump relay------ground

So relay is always grounded now, adding the 12v with key turns on fuel pump

I would not by pass inertia switch, electric fuel pumps can cause a small fender bender to be a raging fire in a few seconds.

l0sts0ul · Feb 7, 2015

Thanks. When I get home I'll work this outnumber the hood.

Now to run the back up lights and neutral safety from the micro switches on my new shifter, I can run ignition power 12+ to one side of each, then from the NSS to the s terminal on the starter solenoid? Then the other to....which wire on the c105 for the back up lights relay?

I was also considering installing an ignition kill switch for the fuel pump TK reduce the risk of it being stolen, any suggestions? Run to the pump? Or the s terminal?

Thanks for the help

RonD · Feb 7, 2015

Best for the kill switch would be the fuel pump relay ground, since you have to deal with it anyway.
And running ground wire is much safer, no shorts, the switch would connect or disconnect ground for relay, so just one wire from relay into cab and get the ground locally, in the cab.

Yes on the reverse lights, no on the NSS hookup.

The NSS passes the 12v to the "S" on the starter relay, and the 12v does come from ignition switch, but ONLY when it is in the START position, you wouldn't want starter to activate every time you put trans in Neutral

If you are running an older distributor and coil that wire to the "S" post on the relay was often spliced and run to Coil "+".
Older Coils will burn out faster if they are given 12v all the time(13.5v with alternator running).
So a ballast resistor was added to give coil about 8volts when engine is running.
But when starting, especially a cold engine, 12v would be provided for the Hotter spark via the "I" post on older starter relays, or via the "S" wire, with a Diode added, diode prevents the 8volts from running to the "S" post.
This gives Coil about 10.5 volts when starter is cranking, voltage is down because of starter motor draw.

l0sts0ul · Feb 7, 2015

Ok. So off the c105 plug how many wires do I actually need coming into the cab thought the firewall? Not that I want to eliminate them all but in trying to clean this up as best as I can.

What would you suggest

RonD · Feb 7, 2015

Couldn't tell you that.

I don't have that model or the electrical diagram for.

Wiring 302 into 3.0

l0sts0ul

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RonD

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