4.0 in a Bronco II

[Rustbucket350]

Ok so I've read the tech articles and faqs but now I'm stumped. I have a 93 4.0 in the Bronco II all bolted up with a 92 wiring harness. How do you splice the Explorer harness into the dash and lighting harness? This might actually need to be in an electrical section but I'm not sure. I don't even see how I'd cut and splice this because ford wrapped all this nice and tight, which is great, except for me at the moment. If I could just use the entire explorer engine bay harness, it would make my life a lot easier. I know the dash won't be compatible but that's fine as long as it runs. The computer is in, the engine is all plugged in, starter solenoid and power distribution box are mounted, but now where do I go?

 

[adsm08]

There are multiple ways of doing it. Some swap dashes, some build adapter harnesses to plug the older dash into the newer engine bay. I am partial to repinning a newer dash harness to fit the older dash.

There is one member here who just finished re-wiring a 4.0 swap by using the adapter method, who said he'd be doing a detailed write up soon.

 

[lil_Blue_Ford]

What year is the Bronco II?

Years ago, I tried doing this in a first gen (1983-1988) and the wiring brought a halt to things. There's more information on it now than there was, so it would probably be easier now. I ended up abandoning the project for awhile and only re-visited things when my choptop was in need of a 4.0 swap to help turn the 35's. wiring in a second gen (1989-1990) is a lot easier. So the 4.0 and wiring went from my 1988 to my 1989 and the 2.9 went in the opposite direction.

I got some extra harness plugs with a length of wire and did some re-pinning of plugs and building adapters. Re-pinning isn't all that hard. Somewhere I have the info on it. When I get a little more mobile I could go looking for it.


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[bobbywalter]

i assume it is an 86 b2?


it is a situation where making the eec stand alone is ideal for the most part. ac and cruise control can be hybrid if you have retained the original transmission ect.

 

[Rustbucket350]

It's an 86 Bronco II and I have no ac at the moment. Manual transmission, basic swap, or so I thought. The Explorer harness is intact from the junkyard and it goes all the way to the giant dash plug with all the lights. I don't want to re-pin because it should just go in. If I have to splice the headlight and parking lights that's ok.

 

[lil_Blue_Ford]

1989 and newer Rangers, Bronco IIs, and Explorers all used the giant dash that has everything. 1983-1988 Rangers and Bronco IIs have a rubber plug in the hole where the giant plug would be that works as a grommet. All the wires come through that and terminate in small plugs. So you either have to splice, build adapters, or swap dashes.


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[Rustbucket350]

The frustration must have clogged my brain last night. I realized I never touched my original headlight harness so I opened up the Explorer one and started removing the light wires. I have everything ran and connected now except the drivers side. I found a pinout of the big dash plug, so I think I can cut that off and splice my original connectors on so I can plug in the dash portion. I'm having a hard time finding out what the four plugs are that come out of the firewall next to the brake booster though.

 

[Rustbucket350]

Anybody know what these are? So far I have power to the interior and lights, but not to the starter or fuel pump. I believe at least one of these should be connected to power the fuel pump.

 

[adsm08]

None of those is power to the fuel pump.

Top most one is for the alternator. If you are retaining the 86 dash harness you can use the 2.9's alternator sub-harness, just leave the big 2-pin plug unhooked and run a short battery cable from the B+ post to the battery or starter relay.

The rearmost plug, the rectangular 8-pin is body harness, so rear lights and fuel gauge and such, that plug shouldn't be affected by what you are doing, find it's mate and plug it back in.

I am not sure about the other two, but something tells me that lower round connector may be for charging as well, again, I am not sure, and seeing the colors of the wires would help.

Fuel pump power runs across the engine harness. If you removed the 2.9 harness you took the plug for the fuel pumps out of the vehicle. The 4.0 harness will have that wire in a black 3-pin that looks like an O2 sensor plug. It will have a green/yellow wire and a pink/black. I think the other one is grey/red, but it seems to change from year to year (I have 5 4.0 engine harnesses from different years and models kicking around my garage).

 

[Rustbucket350]

I ended up tracing the wires from the fuel pump to the grommet and they still look connected, but I obviously removed the relay wiring. On a positive note, the starter now works and the engine cranks. I ended up bypassing the clutch switch even though it worked 4 days ago. Tomorrow I'll see how much of the 4.0 harness I don't need to simplify this process. I think if I can get fuel to it I'll be able to drive it while I complete the dash section.

 

[Rustbucket350]

I went to the junkyard today to grab a fuel line and finally understood the part about making the computer and engine stand alone. I now have fuel and ignition but it won't start. It does try, but I think I made a mistake by only hooking up the frame rail pump. It's a lot louder than it used to be and I think it's because it's sucking air.

 

[alwaysFlOoReD]

There is a low pressure pump in the fuel tank as well as the high pressure frame rail pump. I once had a 86 b2 woith the swap already done. The PO said he used a mustang fuel pump in the b2 tank. I looked and it seemed he filed the pump to tank flange to fit the tank.

 

[Rustbucket350]

Yeah I had fuel at the line when I turned the key but it may not be feeding enough out of the tank to run the motor. Also, I need to hook up the O2 sensor but I doubt that would cause it to not initially start.

 

[alwaysFlOoReD]

Borrow or buy a fuel pressure tester. You need one meant for efi, 4.0l ohv should be at 40 psi.

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[Rustbucket350]

Aha I had no voltage to the coil and the crank sensor wires were all ripped and touching each other. Cranked up today and runs beautiful.