Retrofitting existing EFI harness

[Steve McMahan]

I searched the forum and couldn’t find an answer to this question, but does anyone know an individual or company that either makes a kit or modifies your existing engine/EFI harness to use in a swap configuration? Before I start on mine, I was hoping to run this opportunity to ground.

 

[MKSpeedlab]

Depending on the EFI system there isnt much you need from the original engine harness, and the one main thing(switched power) you usually want to run fresh direct from the battery with a relay to turn it on. I did the Holley EFI on mine and Im not sure I used anything from the engine harness besides the wire for the tach. 

 

[Steve McMahan]

Right, but I want to retain the donor car engine systems. I’m thinking it’s a bit more than the pure EFI wiring. I could be wrong. And, not being sassy, but if there’s not much to EFI wiring, why is it north of $600 for the pleasure? Does that bug anyone else?

 

[detritusmaximus]

You might have to be more specific about the donor car and motor and trans/systems.

Swapping in an old 5.0/5.8 Windsor is probably easier than a later 2.3Ecoboost/4.6 3v/5.0 Coyote. The older ones the harness is more separate from the chassis harness, but I think some extensions need to be made. Depending on what you are doing, there is a base manifold for the 351Cleveland to accept factory 5.8 Windsor fuel injection. The later motors are a bit more complicated if running an auto trans, but Ford did/does sell engine swap controllers and harnesses. That's if you are looking at Ford products. 

Chevy stuff is similar.

Now if we're talking a 2JZ...well, it's such a standard swap in other cars that the info will be out there, but not on this forum!

 

[MKSpeedlab]

Ya I was misunderstanding. I thought you were trying to splice an aftermarket EFI into the original harness. But your trying to splice an OEM EFI setup, which definately has a lot more to it. 

 

[Don C]

It will depend on what engine and EFI system you're talking about. Here is a wiring harness and controllers for a Coyote:

CONTROL PACK - 2011-2014 COYOTE 5.0L 4V MANUAL TRANS WITH SPEED DIAL| Part Details for M-6017-A504VB | Ford Performance Parts

I have retrofitted fuel injected engines into older carbureted engine vehicles, using the harness from the donor vehicle. You'll need the complete wiring diagrams for both vehicles and have an above average understanding of automobile electronics and wiring.

 

[Steve McMahan]

I’m taking a 1987 TBird 5l Speed Density engine and transplanting it into my 73. Am building a wiring board out of peg board to pull the TBird harness on to separate the necessary wiring/systems to use in the transplant. I also want to use the wiring back to the trunk for the relay driven fuel pump and safety switch. Since the cards are about the same size, I hope that helps to made the donor wiring sufficient for the transplant.

I've purchased a wiring diagram and routing diagram for the donor car and have the same for the 73. I’m not an above average wiring or electrical person, but I am patient and willing to stop and ask questions, no mater how moronic they may sound, so it’s done right.

Thanks for the advice so far.

 

[MikeGriese]

When making substantial changes to a wiring harness, I like to document everything about the harness I am changing and the donor harness to make sure that 1) I understand how the harnesses are put together and 2) that I don't miss anything.  There is nothing worse than getting everything routed, installed connected and then find out you are missing one or two critical wires and have to undo a bunch of work.  I use a tool called RapidHarness.  Its purpose in life is to design and document wiring harnesses for production use, but works well for this kind of stuff.  There is a free version that has some limitations in terms of connection counts and diagram counts, but should be plenty for what you want to do.  You can track connectors, locations, wire gauge, wire color, connector color, length (if you want to get that detailed) and a bunch of other stuff.  I like it because I can figure everything out on paper first before I unwrap anything and start pulling wires.   If you go this route, I have already created a library of connector shapes that I'd be happy to send you.

 

[Steve McMahan]

Thanks Mike. I’m going to start with my wire harness jig board and if I get at any point uncomfortable, I’ll be sure to PM you. I’m also lucky to have a resource available to me to help me if I get stumped. One question I did have, beyond just purchasing a junk yard harness, does someone sell like 10’ sections of the typical color coded wiring for Fords? While I don’t anticipate any lengthing issues, it would be nice to have it in hand if that proved to be an issue. I believe one of the values is using this particular vehicle for the swap is the relative size of the vehicles; very close in the dimensions where it counts. I’ll be sure to fully document this process in the build chain so others can avoid anything I do that doesn’t work. While I don’t want to learn the hard way, for some of us, that’s the way we really learn.

 

[midlife]

Rhode Island Wire sells most of the Ford wiring by the foot, but you better make sure you have the right gauge.  https://www.riwire.com/