ECM Code Issue

[franklin2]

Haven't found pin numbers yet, but have found wire colors.

Yellow is battery power coming directly from a fusible link

Darkblue is battery power leaving the relay, this goes to another fusible link and then it changes to red to feed all the 12v electrical for the fuel injection system.

Red/lightgreen comes from the ignition switch, and goes to the coil of the relay

Black/lightgreen is the ground for the coil of the relay. This wire goes to a splice and then heads for that important ground that goes to the battery negative directly.

 

[franklin2]

From what I can tell so far, the two smaller terminals, 1 and 2, are the relay coil. The larger terminals, 3 and 4 are powering the fuel injection system.

If you are putting your meter on ohms and poking around without the power connected, you will get all kinds of readings.

 

[BoomTexan]

I just found this diagram of the full engine wiring harness, will be going over my truck tomorrow and tracing back all the leads from the EEC connection. Technically from a Bronco II, but should be the same diagram. What it's looking like is that between the EEC relay and where it feeds the fuel pump, that fusible link might be blown, could be the cause of that sparking action I was getting.
The Haynes manual doesn't show that, this seems to be the official Ford diagram so I trust it a little more. Gonna go searching for that link, if it's reading continuous, I'll break apart that splitting connection and test for ground at all the individual points, if it's split, then hopefully that could be a solution.

 

[franklin2]

The above is not the official Ford diagram, it's a reproduction that Chilton's uses. It can be used, but does not get into the detail that the Ford diagram would. Best place for the Ford diagram is get one off of ebay in the EVTM book. You will noticed the above diagram shows no connectors anywhere.

 

[BoomTexan]

Alright, the problem has been fixed in the dumbest possible way.
So, both relays I bought were dead, I'm doing the stupid wire hack where I bridge pins 2 and 3 so it's just dependent on the ignition. Will purchase a functioning relay. I did know they both were dead for quite some time.

HOWEVER, and more interestingly, the reason I couldn't bridge the pins before was twofold.

Number 1: somehow, I purchased a fuse holder at Autozone that was DOA. This DOA fuse holder was powering the yellow lead, which goes to pin 4 on the ECM. Fuse was working perfectly, the holder had an internal disconnect. The fun thing here was that when I was getting 12V on pin 1, that was due to a set of yellow wires that were leading to an undetermined sensor. There was a short in them which was causing the wire to receive power, but not enough to actually make anything function. Disconnected the bad fuse holder, unspliced the wires, and we're set.

Number 2: the reason that I didn't bridge the relay was because pin 3 was reading ground at all times. I did try and bridge them before, and was showered in a sea of sparks, so I hadn't tried it since. Turns out, the reason it was going to ground was due to a short in my idle air control sensor. I've just disconnected the sensor and will reinstall the old one, hope that fixes it, but for now I'm running without it plugged in.

 

[franklin2]

What size fuse are you using in the yellow wire? The factory used a fusible link. A fuse that is equivalent to a fusible will be larger than you think. If the fuse you are using never blows, great. But if it does, don't panic and think you have a problem, it might be the fuse is too small.

P.S. For an example you can look at the diagrams for the later vehicles. The factory started using fuses when they were feeding large sections of the fuse boxes, and they are usually around 50-60 amp fuses.

 

[BoomTexan]

Alright, so it's finally working, will replace the fuses and some other electrical stuff soon. Just got up and drove it for a few miles in traffic, got the fuel running through it again, and now it's working just as good as when I first got it. Had a little stumble at first but I think it was just needing to get the spark plugs unfouled.

Thanks everyone for helping me on this! It feels so great to be driving it again, missed this truck so much.
Do have a couple issues still ongoing, but think this one got all wrapped up, and it's thankfully drivable now at least.