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4.0 into 84 Bronco II


85_Ranger4x4

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@Bronson with Bronco ,
To the best of my knowledge, the fuel tanks in BII remained unchanged throughout production, 23 gallon behind the rear axle. I'm using an 89 fuel pump/sender unit as it drops right in the stock fuel tank and is the updated hi pressure in tank pump, just like used in the 94 Explorer's system.
Kind of out of my element here but I know the hole for the fuel pump changed in Ranger tanks for 1985. Before that they were smaller for a simple pickup/level sender. When the EFI 2.3 came out in '85 they made the hole larger to accommodate the in-tank low pressure fuel pump across the board.

I know BII's had a similar efi transition although a year later when the 2.9 came out for 86 and they had the same hokey two pump setup as a Ranger. I would suspect the fuel sender/pump hole transition would be similar as well.

I would be very surprised if a '84 fuel tank would accept a 86+ fuel pump/sender.
 
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@gaz I thought I saw somewhere that the tank hole size changed with the efi system. I'll be dropping the tank in my bronco soon, so I guess I'll answer that question. I think I also need to stay with my '84 bronco sending unit so it'll work with my original fuel gauge.

Did you swap the complete lines from the Explorer into your Bronco? Any issues where they come up over the frame rail near the steering box?
 

superds

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84 B2 was a one year only tank with small opening. 85-90 had the big opening and will fit sender only or fuel pump/sender combos. When I did EFI 5.0 swap in my 84 B2 I used an 85-90 fuel tank, 90 Ranger fuel lines (fuel lines I already owned) and I believe a 90 b2 fuel pump with module.
 
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Thanks @superds!

I started wrestling the fuel system out of the bronco tonight. Fuel lines are out, but I was unsuccessful at getting the rear skid plate bolts out, and so the tank is still in place. I'll give it another go tomorrow after work, when I have a little daylight to assist me.
 

superds

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Thanks @superds!

I started wrestling the fuel system out of the bronco tonight. Fuel lines are out, but I was unsuccessful at getting the rear skid plate bolts out, and so the tank is still in place. I'll give it another go tomorrow after work, when I have a little daylight to assist me.
I went back and read my build thread from 5 years ago to verify what combo of parts I used to make it work, this combo or a variation might work for you as well:

87 BII fuel tank (larger opening for fuel pump)
87 BII fuel sender
90 Ranger in tank fuel pump (tight fit in the BII sender)
90 Ranger fuel lines/filter setup
 
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I went back and read my build thread from 5 years ago to verify what combo of parts I used to make it work, this combo or a variation might work for you as well:

87 BII fuel tank (larger opening for fuel pump)
87 BII fuel sender
90 Ranger in tank fuel pump (tight fit in the BII sender)
90 Ranger fuel lines/filter setup
That's helpful information @superds. I'm thinking I'll be shopping for a tank soon. I'm planning to use the donor Explorer filter and pump, as well as the fuel lines (with modifications to reach the BII tank location).
 
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Looks like my hopes of using the Explorer fuel lines isn't to be after all. The fuel filter lands right at the brake distribution block under the driver's floor. I don't see a way to easily move things around to get it all to fit. But I am still hoping to use parts of the Explorer fuel system. I haven't worked with EFI fuel lines much, so I'll need to do some research on what my options are. I was hoping I might find fuel lines for an EFI BII, but I don't see them being sold anywhere.

Since I encountered that roadblock last night, I decided to drill the broken exhaust bolts out of the exhaust manifolds and tap them, install the new flywheel and clutch, then dropped the motor into place. I used the motor mounts from the 2.8L, and there was only one ear on the top front of the passenger side mount that needed to be cut off in order for it to work. All in all, it dropped nicely into place and mated up with the '84 bell housing and cover plate.

At least some forward progress was made...
IMG_20231205_201018978_HDR.jpg
 
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More progress this weekend.

I got the air box mounted to the passenger fender. I was hoping to be able to use the factory air intake from the Explorer, and anticipated I'd need to cut a hole in the core support to mount it. But, to my delight, there was already a perfect mounting spot already built in just in front of the battery tray! It even had the hole for the mounting screw! I'll take these easy wins any day!
IMG_20231207_175810604_HDR.jpg
IMG_20231207_175800952_HDR.jpg


I also got the starter motor harness installed and the new starter motor. Put on a new oil filter and added oil, temporarily dropped in the battery, then jumped across the starter solenoid to turn the engine over before I put the valve covers on. I did this to confirm my new oil pump was primed and moving oil, and also to get some oil into the top end of the engine before it gets fired up. No smoke, sparks, or flames, but I did get oil flowing nicely from the rocker assemblies.

After that I put on the valve covers and upper intake and connected the throttle linkages. It looks like I only get about 80% throttle with the pedal, so I'll need to look up how to shorten up the cable a bit.

The wiring task is still haunting me. I'm getting a few pieces connected here and there, but I also am getting more and more wire strung out across my garage floor. I'll get there, but I wish it were as easy as the air intake!
 

alwaysFlOoReD

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Look up the "zip tie mod" for stretched accelerator cable.
 
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I find myself a little stuck with the wiring and hoping someone can give me a tow.

First off, I've installed the starter solenoid from the 4.0, but have kept my original ignition wire run to it. This is a black/orange wire with a fusible link near the solenoid. The engine cranks fine this way, but will this cause me other issues? Is the alternative to run the light green wire from the power distribution block and splice it into the black/orange somewhere along its run?

Second issue I'm facing is powering the eec relay. From studying the Explorer wiring diagram I see that the eec relay powers the eec module, edis module, wot relay, fuel pump relay, injectors, idle air bypass valve, and maf. My diagram shows a red/light green wire coming from the START position of the ignition switch going to the eec relay. Then a brown/pink wire from the RUN position of the ignition switch that joins this circuit.
IMG_20231216_160514470~2.jpg


Where would I get this power from on the 1984 2.8L Bronco II? This vehicle had the Duraspark conversion done, and I have two wires spliced together on the driver's side, with a brown wire pigtailed out that connected to the coil. Red wire is powered when ignition is in RUN position, and brown/pink wire is powered with key in START position. These seem like good candidates for connecting to the red/light green wire from the 4.0 harness. And if correct, how would this connection be made?

IMG_20231216_171056856_HDR~2.jpg


As a test, I powered the red/light green wire from the white wire of the ignition module plug, and when key was in RUN position I heard 4 distinct clicks. I'm guessing that was 3 relays and something else? I did get power to the fuel pump from the Explorer when I did this test, but never heard it run (I have the Explorer pump and sending unit on the garage floor while I figure out the wiring). EDIT: It seems I have a bad fuel pump.

Lastly (for now), I've been told I'll need to add a check engine light to my BII interior, but I don't see anything in the wiring diagrams pertaining to this. Any guidance on where it comes from in the 4.0 harness?

Many thanks, and hoping this might help someone else avoid getting stuck in this same mud hole in the future.
 
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Just a little time to work on the Bronco today after church. I got the radiator from the Explorer mounted in. I'm pretty sure I could've run the radiator from the 2.8L, but it had a crack at the upper hose connection and was leaking a little. The Explorer radiator and fan shroud were in better condition.

To get it to work I had to shave the cylindrical posts on the bottom of the Explorer radiator, as they wouldn't allow the radiator to sit down far enough with the lower mounts from the 2.8L radiator. I considered swapping the lower mounts from the Explorer, but that seemed like an unnecessary amount of work. I took off about 1/4" from each post, and that way they straddled the 2.8L lower mounts. The radiator still fit into the rubber cradles on the 2.8L mounts, so I'm comfortable that it shouldn't move around.

This is the shave job I did.
IMG_20231217_140352661_HDR.jpg

This is with the radiator mounted, looking up at the bottom on the driver's side.
IMG_20231217_140845680.jpg

I was concerned that the radiator cap might sit too high for the hood to close, so as soon as it was all mounted my son helped me lay the hood back in place to see if it would close. What a sigh of relief when I realized it would work!

I have some more fuel parts on order, so I should be making some progress on the fuel system this week.

Here's what things look like up to this point. Still wiring to figure out (post #26 above), but progress is being made!
IMG_20231217_163236966_HDR.jpg
 
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Fuel system update:
I'm giving it another go with using the Explorer fuel lines. I like how they wrap up around the frame near the power steering pump, and didn't want to have to build all new lines as it would likely cost more and the routing may not be as clean as factory. The biggest trouble is was seeing was the location of the fuel filter, as it landed right at the brake proportioning valve under the driver floor. With it, the front driveline, and the exhaust, I didn't see room for getting the filter in there. It would either be uncomfortably close to the driveline or uncomfortably close to the exhaust.

My solution is to run this in place of the fuel filter, then install an aftermarket filter further back.
1703347503693.png

This way I can get the fuel lines behind the brake proportioning valve. I have a tubing bender I intend to use on the Explorer lines where needed. I've cut the braided flex lines off the back end so I could add more length (without adding more fittings and opportunities for leaks). Where I cut the 5/16 hard lines I'm using a 5/16 tubing to 6an adapter similar to this.
1703347956039.png


From there I'm using braided ptfe tubing and fittings to include a 30 micron fuel filter, then to the tank.

Speaking of tank, I wrestled with the tank and sending unit for a good while last night. My setup is a new tank and sending unit for an 87 BII. The 84 tank hole was too small for an in tank pump. I cut the wires off the Explorer sending unit and put those into a new connector for the 87 sending unit. The wrestling had mostly to do with mounting the new fuel pump onto the sending unit. It was not cooperating, but in the end I was victorious. 💪
 
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I got the new tank installed today. The old tank was still full of fuel, so I siphoned it out into gas tanks. While I was shuffling the old tank around I discovered a pinhole in the bottom, so the new tank was timely. Mud on the exterior of the tank was keeping it sealed.

I may add some old bike tire tube bits before the skid plate is installed, as it looks like rubbing on the skid plate is what wore the hole in the tank.
 

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