Im new on here so cut me a little slack, but I have a few ?'s about doing an EFI swap on my 1971 Ford Bronco 302. I recently acquired an efi H.O system off of an 87 mustang. its the speed density system and Im having trouble with the wiring. So far ive found all the sensors intact. but now I need to know how to wire in my fuel pump, should I just wire it to my ignition switch like I wired in the low pressure pump for the carburetor? or does it have to be wired up with the engine harness. also I want to wire in my temp and oil pressure gauges, so if anyone has done this with aftermarket 2" gauges before help me out. and lastly where can i find pictures so I can find the O2 sensor connector and how to wire the efi harness into my new painless harness. Thank you for all your help.

 

First of all, welcome.
There are a few of us that have made the swap to EFI, so there is quite a lot of knowledge to draw from.

First of all, are you installing the injection system onto your current 302? The HO shares firing order with the 351W. It will run like this, but for the best performance, you should switch to a 351 cam. You can do some changes with the injector wiring, but it will cause some ill effects because of the computers adaptive strategy programming.

The original Mustang fuel pump was powered by a relay which is controlled by the ECM. Here are the wiring diagrams:

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The factory wiring is set up like this. Power to feed the fuel pump through the relay comes from a fusible link through an Orange/LBlue wire, the fuel pump is fed by a Pink/Black wire. With the key on, the EEC relay is energized which gives 12V through the inertia switch to the fuel pump relay. Comes from a large splice of wires starting Red and then becoming Red/Black after the inertia switch. The EEC relay supplys power to all of the major actuators for the system, including the injectors. The ECM grounds the Tan/L Green wire to energize the fuel pump relay. This wire splices and goes to the EEC check connector for testing purposes.
Hope that helps you. If you need more understanding on how the relays work, let me know.

As for your aftermarket gauges, just leave them wired as they are and install your senders in the new manifold. If you have your EFI harness torn apart, you can route your existing wires for your gauges along with the EFI engine harness. But I usually like to keep them separate for diagnostic purposes.

Your painless harness should have extra wiring to accomodate EFI. You need a crank and run 12V source, a key on 12V source, constant 12V, and grounds. I run my crank and run source from a wire off of the original voltage regulator to a relay. Then I run it, my other power wires and grounds to a sealed junction box. I can't stress enough the importance of grounds. You want to have good ground planes between the bat (-) and the engine, frame, and body.

Jason

 

thanks that helps a lot. but I think the guy that I bought my wiring harness from cut the wires, cause I don't have the inertia switch and I cant see those wires. I did buy a HO cam and installed it already. now I just have to figure out the wiring and that is my weak point. would it be bad to run my fuel pump with just a relay and inline fuse strait off my ignition switch. like I have the low pressure pump for the carburetor? oh also I have a fuel pump out of an 87 f 150 so I can mount it on the frame rails. I dont know if that changes anything?

 

Seems to me that the inertia switches were under the passenger seat in the Mustang. So it isn't uncommon that you don't have the wiring or components.
Do you have 2 relays in a block that would have been mounted on the right fender? One of them is the EEC relay, and the other is the fuel pump relay (if they were together, I can't remember on the Mustang). If the FP relay is there, then you only need to run the pink wire to power your fuel pump(s).
If not, a universal relay can be used and wired like the factory setup was.
I would recommend doing it this way mainly for the ease of wiring. If you let the computer ground the relay to make it work, you won't need a wire going through the firewall. Will make a cleaner installation and less chance for a short.

You may need a low pressure pusher pump to supply the high pressure pump mounted on the frame. The high pressure pump doesn't pull fuel from the tank very well.

Jason

 

yeah I have the low pressure pump already. so I run the pink wire to power and then run the computer ground wire to the fuel pump ground and ill be alright. but I need a special plug for my pump and I dont have that???

 

No, the ECM circuit will not handle the load of grounding the pump directly. It is only meant to energize a low current relay. You want to run constant 12V to the switched side of the relay. Then run 12V power from the EEC relay output (or another crank and run source) relay coil side. Then the ECM pin 22 will ground the relay and complete the circuit between constant 12V and the pink wire going to the fuel pumps. Your best bet is to ground the fuel pumps directly to the frame.

Jason

 

ok so the ecm will just be grounded once I wire it in. and the power from the eec relay??? where do I run that too. the fuel pump??? sorry Im new to all of this so thank you for your patients.

 

Download the wiring diagrams I posted so that you can blow them up and print them. It shows how the circuit should be wired. You should be able to follow them with what I have given you.

Once you have the ECM grounds connected, it will supply ground from pin 22 to trigger the relay through ckt 97.
The EEC relay output (AKA ckt 361, orange/black splicing into several red wires) should have a couple of unused wires. Either going into unused plugs (that plugged into the original Mustang's body harness) or just terminated wires. That wire will go to the coil side of the fuel pump relay.

The output of the fuel pump relay is ckt 787. This is the wire that will go to the fuel pumps.

HTH,
Jason

 

I thought I was told once that I should stay away from the Speed density injection and go with that Mass Air Flow system? Which I thought that the 87 Mustang had?

Tim

 

There is nothing wrong with the speed density system as long as you don't have any major mod plans in mind. In my experience, the speed density system runs smoother than a MAF setup.
All 86's were speed density. 87-88 Federal were SD and Calif equipped were MAF. 89 and up are all Mass Air. This is pertinent to Mustangs only.

Jason

 

Thanks Jason, I pulled a 351w out of a 1989 Bronco that I plan on rebuilding and putting into my 69' and it is the SD type. No major plans for mods, maybe I should go ahead and use it. Thanks for the in put.

Tim

 

The problem with using the truck intake is that it is too tall to clear the hood without a body lift and a hood scoop.

You may have to find an aftermarket Mustang based 351W upper and lower intake and adapt the truck electronics to it. I've gone the other way by using the Mustang injection system with the tall truck intake, so I know it can be done.
Or, you might search for a Mass Air Mustang system and get the upper and lower 351 intake. I think you'll have better aftermarket support this way.

Jason