TBI swap into a YJ wrangler

**Mad Machinist** · 02-24-2014

Since my oldest one rolled his truck, I'm looking into swapping the engine, trans, and transfer case into my YJ. Should be fun.

The truck was a 1995 Chevy K1500 with the 5.7L TBI, 4L60E trans, and a NP241 t-case.

I know I have to take everything attached to the ECM and trans (DRAC included) since it is computer controlled. I have the truck sitting here getting ready to be stripped.

I am thinking about taking the underhood fuse block with the harness as it seems to be the easiest way to hook up the necessary wiring into my YJ. Will this work?

The ECM number is 16200335. I looked and didn't see any information listed on it here. Will this cause a problem?

**EagleMark** · 02-24-2014

The PCM number is probably a GM replacement. Most of those trucks were the 16197427 and $oD for 4l60E and $0E for the 4l80E.

The usual transplant would be to strip the harness down to engine only. Wire in your fused power and Key on power, relays etc... Then just use the YJ harness for everything else without change.

**Mad Machinist** · 02-24-2014

EagleMark,

I think I didn't explain what I want to do well enough. I want to keep the 4L60E as the AX-15 in my Jeep is on it's way out. I also want to keep the NP241 as it is worlds better the NP231 currently in my Jeep.

After spending a lot of time staring at wiring schematics, It looks like it might be easier to keep the underhood fuse block as most of the wires needing hooked up are already there and it also looks like I just might have to supply power to the fuse block from the battery. THis is the way it is currently set up from the factory on the K1500.

The following power wires run to the underhood fuse block:

Eng-1 20 amp, hot in run or start
ECM-1 20 amp, hot in run or start
ECM-B 20 amp, hot at all times

This would leave me with hooking up the ignition wire, which would tied into the Jeep ignition, the check engine light, which I think could be tied into the existing one, and hooking up power to the transmission fuse, which I am wondering if this could also be tied into the underhood fuse block somehow?

**EagleMark** · 02-24-2014

Sounds like a cool project!

**Mad Machinist** · 02-24-2014

I think I figured out how to keep the underhood fuse box.

http://www.wiringproducts.com/200-am...wer-relay.html

With the auxiliary connections available on the fuse box, wiring up some off road lights in the future would be easy.

**1project2many** · 02-24-2014

Howdy, and welcome.

EFI engine swaps are most successful for people who pay attention to details. All of the machinists I know are good because they do exactly that, so I'm betting you'll do well enough also.

Swapping out the 231 is a very good choice. New Venture gear rated the 241 for 5555 ft/lbs of torque vs 1885ft/lbs for the 231. If your 241 has high mileage you might want to split the case and replace the plastic tabs on the range fork. These can wear over time and cause the case to "jump" out of gear.

The trans fuse could be moved to the underhood relay. Schematics indicate several fuses currently connected to battery power which probably won't be used in the conversion. Within the fuse panel GM uses brass strips to connect the supply side of one fuse to the next. This strip can be cut and a jumper installed to an ignition source. Alternatively, if only a handful of fuses are needed one could attempt to locate an auxiliary fuse box and cut down on the required space.

Good luck.

Edit: A relay is a great idea but that one is probably overkill. A 40A relay is more than sufficient.

**Mad Machinist** · 02-25-2014

Thank you for the heads up on the fuse block. Didn't know they used brass strips. Wonder if this is already done since the ECM-B fuse is there and it is always hot.

I plan on going through the 241 since I'll most likely be doing a slip yoke eliminator kit anyhow. Need all the driveshaft length I can get in a Wrangler.

I'll look into a smaller fuse block. Just trying to keep this as cheap as possible. Going to start stripping the truck this Thursday as I'll be off for four days in my normal work rotation.

**1project2many** · 02-25-2014

Hmm... noticed the IGN-E fuse would be available.

**Mad Machinist** · 02-26-2014

Originally Posted by 1project2many

Hmm... noticed the IGN-E fuse would be available.

IGN-E fuse for the trans fuse? May end up keeping the stock underhood fuse block as the fuel pump relay is already there and if my measurements are right, the stock K1500 fuel pump may fit the YJ tank.

**Mad Machinist** · 02-26-2014

Looks like this may be down to connecting three to the YJ harness if I keep the under hood fuse block. One for the ignition, one for the starter, and one for the check engine light.

After almost going blind staring at wiring schematics, I've come to the conclusion that there is some pretty serious power running through the ignition switches and some other switches on vehicles.

**1project2many** · 02-26-2014

Yes, Ign-E fuse for the trans fuse.

After almost going blind staring at wiring schematics, I've come to the conclusion that there is some pretty serious power running through the ignition switches and some other switches on vehicles.

Chrysler transitioned to using low current signal wires on many of their circuits years ago. In a ChryCo product much of what you do is a request... you press the lock button and "request" the bcm to lock the door. Press the window button and you're sending a "request" to the bcm to roll the window up. Even the ignition is that way on many of their cars. GM took much longer to do this and as a result, when retrofitting EFI and other modern conveniences it's important to keep track of how many circuits are being added to the OE ignition. And to make matters worse, many aftermarket switches sourced overseas don't have the quality or life expectancy provided by a 20+ yr old OEM part so adding circuits brings failure even sooner. As you've already suggested, relays are good idea along with common power points.

If you think a '95 pickup has some wiring to stare at, try an Olds or Cadillac from the late '80s or early '90s!

**jdarg** · 02-26-2014

I did this in my 94 YJ three years ago. Put a new 260HP 350 crate motor w/ TBI donated from an 88 Camaro in it.

The stock YJ fuel pump, regardless of whether it was 2.5 or 4.0L, is just fine for the TBI.

The engine harness is pretty much "stand alone" on a 94, so there's no need to even touch the underhood fuse box. Everything you need to splice to is in that engine harness. When all was said and done I literally only had to splice one wire that wasn't in the engine harness and everything merged perfectly with remnants of the YJ engine harness for the cab gauges, etc. I used an 88 Camaro engine harness as the donor. All my gauges as stock and work perfectly w/ the 350, including the tach which I modded with a resistor to make it work w/ v8 vs. i4. Stock Jeep VSS feeds both the dash and ECU. Change the PPM from 2000 to 8000 in the bin. Even though the Jeep VSS was 8v, its fine just feeding it 5v from the TBI ECU and the stock speedo still works fine. Its more than three wires if you want everything 100% functional and stock appearing, but yeah, probably just 3 wires will make it at least drive.

YJs seem to be built for this swap. You really can't even tell it isn't stock. Even the bracket that holds the fan and fuel relays fit into existing holes on the fender with no mods. Just crazy. The splices are extremely minimal because its all in that one engine harness except for one more wire. I have 4.88 gears and maybe 220-240HP and this thing pulls hard through 4000RPM even with the heavy 34" swamper tires I have on it. Totally glad I didn't just go with a 4.0L. Running the AX15 and 231 - the clutch was an absolute nightmare to get right but it finally is right, using stock hydraulics. Third gen Camaro headers fit great although the front shaft gets into the exhaust just ever so slightly. It self-clearanced though so its fine now. I'm SOA if that matters. If you aren't it probably won't enough for that to happen.

You will want some way to tune the computer, I run EBL in mine.

If you have any specific questions about the swap please let me know.

**Mad Machinist** · 02-27-2014

Originally Posted by 1project2many

Yes, Ign-E fuse for the trans fuse.

Chrysler transitioned to using low current signal wires on many of their circuits years ago. In a ChryCo product much of what you do is a request... you press the lock button and "request" the bcm to lock the door. Press the window button and you're sending a "request" to the bcm to roll the window up. Even the ignition is that way on many of their cars. GM took much longer to do this and as a result, when retrofitting EFI and other modern conveniences it's important to keep track of how many circuits are being added to the OE ignition. And to make matters worse, many aftermarket switches sourced overseas don't have the quality or life expectancy provided by a 20+ yr old OEM part so adding circuits brings failure even sooner. As you've already suggested, relays are good idea along with common power points.

If you think a '95 pickup has some wiring to stare at, try an Olds or Cadillac from the late '80s or early '90s!

This is kinda what I am worried about. My Wrangler is an '87 with the 4.2L. lots of power through 27 years old switches could get a little toasty.

**Mad Machinist** · 02-27-2014

Originally Posted by jdarg

I did this in my 94 YJ three years ago. Put a new 260HP 350 crate motor w/ TBI donated from an 88 Camaro in it.

The stock YJ fuel pump, regardless of whether it was 2.5 or 4.0L, is just fine for the TBI.

The engine harness is pretty much "stand alone" on a 94, so there's no need to even touch the underhood fuse box. Everything you need to splice to is in that engine harness. When all was said and done I literally only had to splice one wire that wasn't in the engine harness and everything merged perfectly with remnants of the YJ engine harness for the cab gauges, etc. I used an 88 Camaro engine harness as the donor. All my gauges as stock and work perfectly w/ the 350, including the tach which I modded with a resistor to make it work w/ v8 vs. i4. Stock Jeep VSS feeds both the dash and ECU. Change the PPM from 2000 to 8000 in the bin. Even though the Jeep VSS was 8v, its fine just feeding it 5v from the TBI ECU and the stock speedo still works fine. Its more than three wires if you want everything 100% functional and stock appearing, but yeah, probably just 3 wires will make it at least drive.

YJs seem to be built for this swap. You really can't even tell it isn't stock. Even the bracket that holds the fan and fuel relays fit into existing holes on the fender with no mods. Just crazy. The splices are extremely minimal because its all in that one engine harness except for one more wire. I have 4.88 gears and maybe 220-240HP and this thing pulls hard through 4000RPM even with the heavy 34" swamper tires I have on it. Totally glad I didn't just go with a 4.0L. Running the AX15 and 231 - the clutch was an absolute nightmare to get right but it finally is right, using stock hydraulics. Third gen Camaro headers fit great although the front shaft gets into the exhaust just ever so slightly. It self-clearanced though so its fine now. I'm SOA if that matters. If you aren't it probably won't enough for that to happen.

You will want some way to tune the computer, I run EBL in mine.

If you have any specific questions about the swap please let me know.

My Wrangler is an '87. It WAS fuel injected, if you could call it that. I did the Nutter Bypass which eliminated the ECU and then put in a HEI ignition. All wiring attached to the ECU is gone.

I'll dig into the wiring a little more tomorrow. Keeping the 4L60E complicates this a little. I start my four day weekend tomorrow so I'll have time to play with it.