I took some time yesterday to start sorting through the mess of wiring that Ford installed in this Bronco. Some of the plugs that were mounted on the drivers side inner fender already had some wiring cut but were still there. There was an EEC (Engine Electronic Control) relay that I removed; rewiring the fuel pump relay to be energized directly from the ignition switch rather than through the EEC relay. There was a STO (self-test output) plug that is gone. I also removed the HEGO (heated exhaust gas oxygen) and MAP (manifold absolute pressure) sensors. There's plenty more to remove, I just ran out of time. It doesn't look like it, but I've got about seven hours into this.
Another issue: the previous owners. I think we've all been guilty of this (I know I've done it): wiring in something; a trailer brake controller, a relay, whatever, and not doing a very good job routing the wires. This leads to individual uncovered wires wires running every which way. It looks tacky. There are splices that have been made into three and even four wires that run only a few feet.
I am NOT guilty of that particular sin, I have always been **** about the amount of splicing I make. But when you are going through a vehicle that has probably had at least five owners, you're going to find some hokey stuff. (BTW, the wire nuts are temporary.)
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One of the problems with the method I'm using is the source of information: the Haynes manual's wiring diagrams I'm using are NOT intuitive, to say the least. There's ten pages of wiring diagrams for the 1990-91 F-Series and Broncos. The issue for me is when I follow the line for a particular wire to an individual component. It will refer to the component as (for example) 'A/C clutch resistor diode.' But the diagram doesn't give any reference to where the individual component is broken down in further detail on another page. This leads to a LOT of flipping around to find the individual component somewhere in the diagrams. Also: there's no reference to where the component is physically located on the Bronco. This is not a big deal; the engine compartment isn't very big. But add it all up and it's a time-consuming process.
The good thing is, I'm learning. I can now look at the wiring diagrams with a little familiarity; they're slightly easier to follow. A good move that Haynes made: the relays are shown in detail. This allows me to identify what wire is doing what, and is the reason I removed the EEC relay. It was energizing a whole bunch of engine control crap that is no longer needed. Also, I have realized an engine bay fuse block is necessary to eliminate the fusible links that Ford installed on the starter relay. Fusible links are old school tech. From what I read, no vehicles manufactured since the early 90s have had fusible links, they all have fuse blocks.
Another wrinkle: there is what's referred to in the wiring diagrams as a 22,000 ohm ignition suppression resistor in the tach circuit. Actually getting my hands on it revealed that it is labeled as an 1800 ohm resistor rated at a 1/2 Watt. (Surprisingly, it is about six inches long.) But it is ALSO labeled as 22K 1/2 Watt with no ohmic value. ***? Why the discrepancy? The wiring diagrams appear to show one in gas AND diesel applications. I believe the reason it's there in a gasoline application is because the coil creates magnetic waves that can interfere with tach operation. As we all know, in a diesel application there is no expanding and collapsing magnetic field.
Is this resistor necessary for a diesel?
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As you can see, there is some copper that isn't necessary now that the 5.0 is gone. This small pile will get bigger.
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My plan is to have a clean engine bay; the few wires that are present will be neatly wrapped in cloth tape and wiring loom. It won't be show quality but it will look nice.
