LS3/6L80e Engine Swap into my 73

[WPS 73 Bronco]

Tires are 33”.

Found a guy to complete the custom install of my exhaust. He’s planning on ditching the SS band clamps that came with the Duff kit, and I agree since it eliminates leak risks. This weekend I will trial fit the drivers side power step so that when he does the exhaust next week, we will know what potential issues we will have with interference.

Other projects for the weekend will be to finish out my fuel vent system with the Vapor Trapper and button up wiring in the engine bay. This could also include cranking the engine for the first time, without fuel.

 

[WPS 73 Bronco]

Got my drivers side power amp step mechanically installed. Needed to get this done since I’m getting the exhaust installed this week.

I decided I’d power up the Holley Terminator X and crank it for the first time. Previously I’d checked out the existing Bronco wiring and all was good.

The Holley system powered up and went through its start up process. I couldn’t crank it because I don’t have the neutral switch wired.

How do I jumper it out?

 

[WPS 73 Bronco]

I’ve got another question. I’ve got all my kinds of items connected to my starter solenoid. I’m not an electrical guy, so I’m questioning if I’m doing this all correctly. Now that I’ve got the Holley terminator system, do I even need the starter solenoid?

 

[WPS 73 Bronco]

So I’ve answered some of my own questions. I did have the solenoid wired wrong. Here’s how I think it works. Power from battery on the left post. Power from the right post feeds the starter.

I have on my original wiring harness i have a brown and a red/blue wire. I have the red/blue connected to the first small post, and the brown to the second one.

I also have several other wires on the positive post that feeds the starter. One is powering a relay thats tied into my horn that’s not working. I also have the below wire that is black that says fuseable link. I have no idea what it is or if it should be attached here.

Can I use the positive feed side for all direct battery + connections or should I install a separate power distribution block?

Is the output side of the solenoid considered a switched power connection that I can use for other ACC connections?

 

[DirtDonk]

The black wire with fusible link does go on the battery side of the starter relay. Without it, nothing inside your truck will work. Period…

Yes, you can use a separate power stud, or terminal stud, or power, distribution stud.
Adding one is mainly just to take some of the clutter off of the starter relay’s battery side.
But if you only have a few wires there and they all fit, then there’s not really any dire need for a separate power distribution stud.

And yes, keep the existing Ford starter relay in the system. That’s usually a best practice, because it’s still there to take the load off of the ignition switch for activating the starter. And, as you found out, it’s there to attach constant power items too if needed.
Even with a modern PMGR starter, which it sounds like you might have?

Looks like the two small wires are in their correct locations. The red with blue wire goes to the “S“ post and the brown wire goes to the “I“ post.
The red with blue wire is the one that energizes the relay to crank the starter. That’s the one that your neutral safety switch would go to.
If you’re not getting power on that wire, with a factory harness, there should be a connector behind the engine near the firewall with two black w/red wires, and two red w/blue wires.
That’s where the jumper goes. Between the two red with blue striped wires.

 

[DirtDonk]

You might have to check that fusible link. It got melted at the end somehow. That’s usually by overheating and doing its fusible link thing. If it’s not burned, perhaps it was just rubbing on something viciously. But check it, feel it, squeeze it, and then check with an O meter to make sure It’s still working.

With a stock harness, the fuse panel is woefully inadequate for modern conveniences. With a stock wiring harness, there aren’t enough grounding points, so you will have to add quite a few. With so many posts and so long of a discussion, I don’t remember what we’ve talked about.

What year is the bronco again? If it’s not a 73 or newer, then the neutral safety switch wiring connector that I mentioned does not exist.

 

[WPS 73 Bronco]

73 Bronco and I replaced the factory fuse box with modern universal.

 

[Yeller]

With so much of the original using the factory solenoid it is hard to justify not using it unless the only thing it does is run the starter. To keep it, run a jumper wire from the battery cable post on the starter to the start terminal on the starter. That way you don’t have to reroute and/or extend other wiring to the starter. With the jumper wire the only wire you need to the starter is the battery cable from the solenoid, it will work just as Ford intended.

 

[DirtDonk]

73 Bronco and I replaced the factory fuse box with modern universal.

As long as the rest of the harness is intact, then that 4-wire connector should be there behind the intake manifold. Within reach of a neutral-safety switch pigtail/harness when present.
There are pics hereabouts on the forum showing the jumper. Plenty of discussions, because it's often a failure point when trying to track down a no-start condition.

I think member FordBronc has posted them up over the years.

Paul

 

[Oldtimer]

I also have several other wires on the positive post that feeds the starter. One is powering a relay thats tied into my horn that’s not working.

To be clear, the wire powering horn relay goes on battery side of starter relay (solenoid).

Is the output side of the solenoid considered a switched power connection that I can use for other ACC connections?

Output side of starter relay (solenoid) is only for starter.
Switched power for Accessories is obtained from back of ignition switch.

 

[DirtDonk]

The Horn relay also has a fusible link. But it’s a yellow wire, and would probably not be present on a 73. That was, I believe, a running change in 74.

 

[WPS 73 Bronco]

Okay, so I think I understand.

Battery side of the solenoid is only for the battery and any other item needing constant battery connection. The solenoid post is only for the starter.

There is no ACC connection on the solenoid.

Thanks for all the help.

 

[Grey owl]

After a lot of evaluating what engine swap I wanted to do, I finally pulled the plug and bought an engine & transmission. I was deciding between a 408, a Godzilla, or the LS swap. Ultimately, I went with the LS, recognizing the push back I’d get from a majority of the Ford guys. I have experience with LS swaps as I did one 10 years ago on my 72 Corvette.

Here’s some pics of the motor and transmission. It’s a built LS with Texas Speed Stage 2 cam, Mahle Forged Pistons, Scat Rods, ARP Head bolts, rod bolts and main studs. The work begins today as I completed my last cruise with the 302/C4 on Friday. I’m sure I’ll be looking for lots of help.

Thanks in advance for the help and support.

Hmm, interesting decision, challenging swap. Personally the Coyote would be my choice. Just not a fan of GM transmissions. Best of luck.

 

[WPS 73 Bronco]

Well, I was hoping for success. Didn’t happen. Got everything wired up correctly. Red and blue wire is on the motor starter side of the solenoid, with the brown on the battery side. All grounds are solid for the battery and the wiring. When I turn the key on, not starting, everything powers up. Everything is powered up and I can control of the VA blower, wipers, lights, Dakota Digital, etc. The Holley system also starts up, handheld screen is working along with the Xmas tree lights on the ECU. I’ve tied a jumper from the yellow Holley neutral switch wire to the red/blue connection on the starter solenoid.

When I turned the key to start the motor, all systems seem to short out and restart. See attached video.

 

[Oldtimer]

Need a picture of starter relay showing wires and marking on case.
I think you have RD/BL and BR wires backwards. But need to see battery wire and starter wire orientation.

 

[WPS 73 Bronco]

 

[WPS 73 Bronco]

In the pic, red/blue is on the right which is where the cable to the starter goes. Battery is on the left. I did have them backwards. I switched them and same exact problem occurs.

 

[Oldtimer]

Stud on left is from battery, like you have.

Stud on right is to starter, and nothing else, like you have.

The S post should have 12v supplied by key in START position (RD/BL wire). Jump the S post to battery positive, and relay should close (klick). Relay ground is thru mounting bolts on fender. I always add a ground wire back to frame/battery negative terminal. Between 50 years of rust and paint, fenders may not be a good ground.

The coil gets reduced voltage when key is in RUN position, because of resitance wire (ballast resistor).
The I post is 12v when relay closes. This is to supply full battery voltage to coil during crank of starter. The BR wire is the wire that feeds coil.

Not sure what your light blue and purple wires are for, but they will only get 12v when key is in START position, no matter if they are on the S or I post.

I would put the battery cable on the left post first, then the feed from the alternator second, followed by the rest of the wires that you want connected directly to battery feed.

 

[WPS 73 Bronco]

Did the jumper test and got the click. Nice and loud.

i have another interesting issue. With key on i have power to my brake and blinker lights. Extremely low power as they are barely on.

 

[Oldtimer]

Should get the same click when key is turned to START, and starter motor should crank motor (on a Ford).
Haven't worked with Chevy starter circuits in 40+ years, don't remember how they are wired.