84 B2 2.8L swap to 92 4.0L - transmission and wiring questions

[franklin2]

Ran into a little snafu today. I didn't know it (all you guys probably do) but the motor mounts are different between a 84 2.8 in a Bronco II and a 86 2.9 in a ranger pickup, both 4x4.

I had the 2.9 almost in the 84 but it didn't want to line up quite correctly. Suspicious I got on rock auto and looked both up and sure enough, the motor mounts were different. I still had the 86 truck here, contemplating on taking the mounts out of it and putting them in the 84 BII. But then I had a eureka moment. If the blocks are the same, can I take the 84 motor mount brackets and put them on the 86 engine? Did it, and it went right in.

 

[Bronson with Bronco]

If the blocks are the same, can I take the 84 motor mount brackets and put them on the 86 engine? Did it, and it went right in.

This is what I did with my 4.0 going into the 84. The only modification needed was to take a bit of the corner of one of the mounts off with a grinder. Believe it was the passenger side.

 

[Bronson with Bronco]

A CEL Bulb gets 12volts from the instrument cluster with key on, but bulb is not Grounded so stays OFF
When the computer(EEC) powers up, also with key on, it will Ground the CEL bulb turning the CEL on, which means Computer has Booted up OK

Pin 17 on the 1992 Computer's 60 pin connector is that ground for CEL bulb

Computer was usually in the cab, in passenger kick panel area, and it's wiring harness ran thru the Firewall on passenger side of the engine bay
On that main harness, in the engine bay, is the OBD1(VIP) test connector
Its where you would plug in an OBD1 Reader

Looks like this: https://www.therangerstation.com/tech_library/images/eec-iv_testing2.gif

A 6 slot connector and a single slot connector
On the 6 slot connector the Self-Test OUT is the CEL ground from pin 17
So you could "tap"/connect your added light there, run a wire from this OBD1(VIP) slot thru the firewall into the cab
Mount your light and connect it to a 12v key on power wire, and to the new wire

Some newer lights are LED, so have a + and - wire unlike "regular" 12v bulbs
Test any new bulb on your battery terminals to makes sure it lights up with either wire on either positive or negative

This is GOLD!

I ordered the CEL I posted above. It's an incandescent lamp. I'll let you know how it goes, but it may be a week or so until I tackle this.

 

[Bronson with Bronco]

First start up today! However, it was very briefly enjoyed.

As soon as the motor fired it ran up to WOT, so I shut it down. Tried it again, with the same result. The accelerator pedal wasn't down (I didn't even touch it), the cable wasn't stuck, and the throttle body wasn't open.

This is the first fire after swapping in the 4.0L in place of a 2.8L. Possibly something with the computer that isn't happy? Any help is appreciated.

 

[franklin2]

The engine can't run up that high without air. Air is coming in from somewhere beyond the throttle blades.

 

[Bronson with Bronco]

The engine can't run up that high without air. Air is coming in from somewhere beyond the throttle blades.

Thanks!

I plugged off the vacuum lines from the brake booster and cruise control, as they seemed suspect. Started it back up and it found a nice idle after a few moments. Now to see which of those two was the culprit. With as high as the idle was, I didn't think it could have only been vacuum related. Live and learn...

 

[Bronson with Bronco]

Today the Bronco moved under it's own power! I even put the hood back on!

However, the engine is running extremely rich and wanting to die. It doesn't improve when it gets up to temp. I have all the doors and windows in my garage open, and it's making my eyes water.

It has a new O2 sensor installed. I'm not getting any codes (other than those related to the now non-existent automatic transmission). I've checked vacuum lines and think I'm good there. I've searched this forum for "running rich" and haven't found what would seem to be a comparable thread. Any advice?

 

[franklin2]

A major player in engine fueling on that setup is the mass air flow sensor. I would pull some codes and see what the computer has to say about it.

 

[Bronson with Bronco]

A major player in engine fueling on that setup is the mass air flow sensor. I would pull some codes and see what the computer has to say about it.

I pulled codes earlier today and only got codes related to the absent automatic transmission. Is there a way to test the MAF sensor?

 

[franklin2]

You must not have run it long enough for it to go through a drive cycle. You would think you would have gotten rich codes.

 

[Bronson with Bronco]

I think I'm getting closer, but still having troubles. Bronco is currently dead in the water, with no eec relay closure.

Last night I had it running with the intention of getting it up to temp and checking engine run codes. While it was warming up I noticed a coolant leak from the water neck, so started fiddling with that. In the process, the Bronco died. I didn't go around and turn the key off, but kept fooling with the heater hose, and heard the relays click. Then they went back off. I wiggled the harness at the front of the intake, and it happened again. I then narrowed it down to the crank position sensor loom going down the front of the engine. The slightest nudge here would cycle the relays. Maybe this is why it's been running so poorly?

I then peeled back some of the split loom, and then saw some arcing against the alternator bracket. I unhooked the battery, exposed the wires, but didn't see that either of the 2 crank position sensor wires were damaged. I'm guessing the bare wire is a shielding wire? This must have been what was arcing. Now, after taping it back up and putting it all back together, I can't get the eec relay to close.

Back probing the relay with the key on, I get
Y wire 12.9V
R wire 11.8V
R/G wire 12.8V
B/W wire 12.3V

Any help on what might cause this and where to start troubleshooting?

 

[RobbieD]

Digital multimeter (DMM)? Test again and look for a "-" (negative) symbol in front of some of the numbers.

 

[bobbywalter]

what color was the wire?

no crank signal no start

 

[franklin2]

Sounds like a grounding problem. It was using the shield. which is grounded back at the ECM as a ground for the power. The arcing was the circuits and the PCM using the shield to complete the circuit. Now you fixed that you do not have a good ground to the system. Using the shield as a conductor certainly can introduce noise and make it run lousy.

Now the question is, how was the original 4.0 system grounded? I know on my 1986, there was a dedicated ground wire for this circuit going directly to the battery negative terminal. It had a single disconnect connector in the ground wire. If you pulled this connector loose while the engine was running, it would stop dead.

 

[franklin2]

Here is a grounding diagram for a 1992 Explorer. Looks like they did the same thing, a main ground in that harness going directly to the battery. And looks like there is another ground going somewhere else also.