Wiring harness EFI
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Elder User
Joined: Feb 2003
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From: New Braunfels TX
Wiring harness EFI
I'm pulling the wiring harness out of a 86 grand marquis for the EFI, do I need to also pull the wiring that goes to the fuse box or just the part that goes to the computer. I'm going to be installing the engine (302) and transmission in my 51. Other wise some one told me they sell a wiring harness so that ya just have to pull the components. Is this true? The pile of wires on the cowl is getting pretty high. Hope I'm not getting in over my head, never did any thing like this before.
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Joined: Jan 2003
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From: Rochester, NY, USA
Hi fordman102,
This is a topic near and dear to my heart. I spent a total of 10 hours last week sitting on my dining room floor with wiring harnesses, diagrams, and schematics spread from wall to wall. My suggestion would be to grab everything that you can. You can always throw away the left over stuff later.
The main harnesses that you will need are:
*main engine harness
*efi harness
*O2 sensor and tranny harness
All the other wiring can be made by using a universal street rod fuse panel.
I'm currently shopping for the O2 harness because I didn't grab it from my donor car. Also, make sure you grab the fuel pump relay and wiring. I know it's under the drivers seat on a Mustang, but I don't know where it is on a Vic or Marquis. This is all still very fresh in my mind if you have more questions. Thanks - Brad
This is a topic near and dear to my heart. I spent a total of 10 hours last week sitting on my dining room floor with wiring harnesses, diagrams, and schematics spread from wall to wall. My suggestion would be to grab everything that you can. You can always throw away the left over stuff later.
The main harnesses that you will need are:
*main engine harness
*efi harness
*O2 sensor and tranny harness
All the other wiring can be made by using a universal street rod fuse panel.
I'm currently shopping for the O2 harness because I didn't grab it from my donor car. Also, make sure you grab the fuel pump relay and wiring. I know it's under the drivers seat on a Mustang, but I don't know where it is on a Vic or Marquis. This is all still very fresh in my mind if you have more questions. Thanks - Brad
Hotshot
Joined: Oct 2004
Posts: 15,882
Likes: 88
From: Durham NC
AFAIK all EFI is computer controlled, so you'll need the computer as well as all the sensors and wiring. If you want to simplify your life, several wire harness companies including Painless sell an EFI harness for non computerized vehicles that includes a dedicated EFI control computer chip. The problem with OEM computers is that a lot of the non EFI functions are interrelated, so not having the seatbelt or airbag sensor hooked in the circuit for example can shut down the computer.
Don't forget to get the in tank fuel pump as well.
Don't forget to get the in tank fuel pump as well.
Hotshot
Joined: Oct 2004
Posts: 15,882
Likes: 88
From: Durham NC
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Hotshot
Joined: Oct 2004
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From: Durham NC
I was just fixing yellowducman's URL, he found the site.
I'm not running a Ford engine, but I did look over the site and it did look really informative.
I'm not running a Ford engine, but I did look over the site and it did look really informative.
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Brad!?!?!
hey brad, i know exactly what your going through too. I am in the process of converting my 86 150 4.9 to a efi 4.9. I grabed a complete motor form a mid 90s e150 and a motor and fuel wireing harness form a 88 f150 along with a computer. Iv been trying to get this thing to run for weeks now. i got spark and fuel pressure however my injectors arnt geting the proper voltage!!! I belive the problem is the computer is not geting current form the ignition. What did you do with your ignition?!?!?!?!?!?!?
Postmaster
Joined: Sep 2005
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I intend to do the same thing in the spring. I have an 86 t-bird lined up as the doner. I have been on that site as well as several t-bird/cougar and mustang sites just reading for the last few weeks. Keep us all updated on your progress.
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Joined: Jan 2003
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From: Rochester, NY, USA
weswes01,
I know that the computer has a 12v constant lead and it also had a 12v switched lead that turned the computer on. I ran 12v constant power to all of the relays (EEC, Fuel Pump, O2 sensors, ignition/TFI). I then ran 12v switched power through the ignition switch to fire the relays. Make sure that your getting a good 12v into your EEC relay that powers the injectors. I'm not sure how much different your set up is than mine but It is at least a start.
Take a look at the relay wiring diagrams on http://fordfuelinjection.com/?p=6. These were a life saver.
Good luck - Brad
I know that the computer has a 12v constant lead and it also had a 12v switched lead that turned the computer on. I ran 12v constant power to all of the relays (EEC, Fuel Pump, O2 sensors, ignition/TFI). I then ran 12v switched power through the ignition switch to fire the relays. Make sure that your getting a good 12v into your EEC relay that powers the injectors. I'm not sure how much different your set up is than mine but It is at least a start.
Take a look at the relay wiring diagrams on http://fordfuelinjection.com/?p=6. These were a life saver.
Good luck - Brad
Senior User
Joined: Jan 2003
Posts: 369
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From: Rochester, NY, USA
I don't have a fuse panel yet so i took my power right from the starter switch. Constant 12v went right to the computer and switched 12v went through the ignition switch. Once I get the fuse panel in, I will rewire it so it's all fused.