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Official 4.0 swap thread

179K views 466 replies 98 participants last post by  locohosa 
#1 ·
Well, I saw that their was an AMC V8 thread, so I figured I would try and start a 4.0 swap thread here. Feel free to ask any specific questions you have, as I am sure I will miss some things. Let me know what you think and if thre thread should be a sticky.

Engine mounting
Well, their is some good news here. Your CJ 258 motor mounts will work. You do not need to move any mount brackets, or even change the actual mounts.
Flywheel/flexplate
Depending on how you plan to mount your CPS (Cam Position Sensor) you may be able to keep your factory 258 stuff, or you might have to get a 4.0 wheel. If you get a CPS relocation kit from HESCO, you can keep the CJ 258 flywheel and starter, it will bolt right on to your 4.0. If you plan on using a CPS in the bellhousing, you need the flywheel and starter for a 4.0 as the CPS reads the tick marks off the 4.0 flywheel.
CPS Options
The two main options for your CPS are the HESCO relocation, and the factory. The HESCO is located herehttp://www.hesco.us/shop.asp?action=details&inventoryID=43098&catId=7902 or you can use a sensor in your bellhousing. If your bellhousing wasn't mated to a 4.0 from the factory, don't fear. Novak will drill up your bellhousing to be able to put in a factory CPS sensor for around $75-$100.
Cooling
Some more good news here. You can use a factory CJ 4.2 radiator for your cooling. Depending on what donor you get your 4.0 out of, yo may have an off-set fan. If your fan is off-set, you just need to get a wrangler water pump, fan, and fan clutch to center it all up. You can also use your factory CJ 4.2 radiator hoses
Wiring
Here is where everyone freaks out. It is daunting, but once you figure it out, it becomes second nature. It freaked me out at first, but once you have everything laid out it is not difficult. Their are only 5 wires on your Bulkhead that you really need to keep. They are the Check engine light, tach signal, ignition circuit, the fused battery ignition for the CJ fuse panel, and the starter relay. It's as simple as getting a factory manual for your particular harness and finding those wires. Make sure you get one for your exact year, as wiring changed a little every year that I have seen. You can then cut out all the other wires from the bulkhead and cut them off either where they go into a connector or where they go in to a splice. You need to find and splice a few wires in the CJ harness. They are 1.) 12volts from alternator to CJ fuse block (red)
2.) ignition crank wire (blue)
3.) ignition run wire (red with white stripe)
4.) fuel pump wire (not from CJ harness - you need to run this wire yourself based on what fuel pump set-up you use) You can also cut out any headlight wiring you may get. It doesn't really matter if you g e an auto or 5spd harness if you are 5spd. If youg et an auto harness you will just need to put the park sensor wire on a switch that you flip to make the jeep think you are in park or drive to crank. If you just ground this wire the computer will not receive a signal from the MAP sensor and will hardly move.
VSS(Vehicle Speed Sensor)
Their is a debate over if you need a VSS, I plan to get one. It will surely make your Jeep run better, and get better gas mileage. You need to get one with the electrical and mechanical hook up if you plan on using the CJ speedo. One from a 91 YJ will work, and from a late 80's Dodge Dakota.
Fuel Pump
You can do an in-tank, if you get a fuel sending unit from a TBI 4 banger YJ and the actual pump from a MPI 4.0. You will need to figure out wiring up the sending unit to make your gas gauge work, as it is exactly opposite of a CJ sender. You can also go external. That is my personal thought. Most guys that do the swap go with an External E2000 fuel pump. It was used in ford vehicles for many years. You need a pre-pump filter and post-pump filter. The pre-filter can be a standard filter, but the post needs to be a fuel injection rated filter. Also, you MUST have fuel injection rated hose where you use flex line. This stuff is several dollars per foot, but you need it to take the pressure. I also recommend fuel injection hose clamps for all connections. Ideally you need 5/16 line to the rail and for the return, but I think 1/4 on the return will work alright.
Ok guys, this is the gist of it. If I missed anything, feel free to reply asking questions, I will answer them to the best of my ability. This pertains to the OBD1 swap, as that is the one I have experience with. Let me know what you think, and if this should be a sticky.
 
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#151 ·
is a cj7 or 5? a 5 is to short to use the aw4 that's stock in most gc. a 7 you can use the aw4 but it will require new longer and shorter drive shafts. check Novak for an adapter for the d300. you'll have to weigh the cost of new parts to make the longer auto work. you'll also have to increase the length of the d300 linkage, and new cross member for the tranny. lots of things to consider.
 
#152 · (Edited)
Wow thanks your cleared up a lot of the points I was worried about. It is technically a YJ tub but the chassis is CJ-7. Drive shafts are not a problem we have a place localy that can make us whatever length we need and already repaired a twisted and snapped drive shaft tube once on it. Cross member I think we can manage w/ some scrap metal and a welder lol. The only thing I am not sure about is the linkage. What kind of parts are we talking about to lengthen the linkage? The reason we want to go auto is because it has a plow on it and plowing is just easier in an automatic. Plus the clutch we had to put in it to handle plowing makes it almost undrivable for me. Mainly because the seat doesn't move forward enough for me. Another question? The GC transfer case doesn't have the drive shafts coming out from the right side that we want and will not work w/ the CJ axle's correct? Thanks for all the info you have already provided.
 
#153 ·
Novak can adapt the AW4 to D300. No big deal. The GCs had a lot of 44REs-- 46REs. I don't know if they adapt those.
 
#154 ·
i don't know if they are the same between the 4.0 & 2.5. a parts # search would answer that. the cps from auto to manual are the same, but the location id different. use the link i gave you to cjoffroad. use the search on the forum. there is 1 master chrysler tech that signs in all the time. marty socal. you'll be able to tell from his responses.
 
#155 ·
Has anybody on here done the 4.0 head/MPI swap on the 4.2 and used the wireing harness from the 4.0? I am getting ready to do that part of my swap and I cant decide if I want to do the wireing harness myself or buy the one from hesco. I rather not spend the 500 bucks!
 
#156 ·
Save the 500 bucks.
 
#157 ·
That is why I am posting this. the problem is that I suck at electrical. I am doing a complete frame up and I dont want to burn it up on some crappy electrical work. So if there is anybody out there that has done this please let me know!
 
#158 ·
To do a head swap you need what: ECM, PDC, and all the sensors. So, yes I have done this it's all reattached to my 4.0 I swapped in. Are you also stroking it? For anyone who doesn't know what I'm talking about I am not coming on to him.
What part of the wiring are you afraid of thinning, soldering, or just the general transplant?
Thinning is not that hard. Get a FSM or access to AllDatta. The hardest part of thinning is removing the miles of electrical and friction tape the Mexico factory that assembled the harness used. All I did was label (with masking tape) any component I wasn't swapping or using and tug and trace it all the way back to it's source before I cut it out. I recommend labeling everything your keeping, relocating, or removing, before you cut any thing. If you don't you will have to splice it back in (and I did) when you find the splices that run through the harness. Lots of wires are common wires used by different sensors. If you just mark the brn/ylw (note: NEVER CUT THE BRN/YLW) from the component you're removing then at the ECM and cut when you pull the wire you'll find 1 to 2 splices tied in that go to things that were staying. I'm not trying to scare you. You just need to take your time and look at whole picture. What's your time worth $500?
Soldering is easy. Do it right with solder and heat shrink. The trick I use for soldering is plumbers flux. It's the paste you put on copper pipes when you sweat (solder) joints. Twists your wires then apply some flux now coat your iron with solder and touch it to the wires and flux. It will literally suck the solder up into the wires. With the iron on the wires add solder to them as needed to finish coating the connection. Flux makes anyone's connection look like they were done by a pro.
If you were worried about the transplant the Hesco harness wouldn't be any different
It might help if we knew what year head you were swapping. Someone my have the FSM on disk or PDF, or have thinned the same harness.
 
#159 ·
somebody, the nv231 is out of the question for your axles. I thought about swapping the AW4 and 231 in my swap. I was going to run the 231 inverted to match my drivers diff drop. Can't be done the D300 is the only case you can run inverted. On the linkage just replace the rods in the t-case shift linkage with ones that are long enough. I can't tell you the length. It's going to take a little fab work on your part once installed to find the throw you need.
 
#161 ·
Well lastboyscout, here is what I have........

93 head resurfaced, new springs and valves, ported and polished
93 wireing harness from a cherokee
92 intake manifold, injectros and TB
92 exhaust manifold

Well i serched e-bay for the hesco wireing harness and I found one, it has a couple days left and its at 100 bucks. I am going to keep my eye on that and if I can get it for around 250 or 300 I am going to buy it. I have a ton left to do on my project and anytime saved will help alot.

The things that I am worried about on the wireing is not knowing what I need to keep and what I need to get rid of. I have everything except for the computer right now but I have my eye on a couple right now. And that brings up another question, will just one for a manual work since I am running the Ax15 or can I use an auto? Any help would be great!
 
#162 · (Edited)
I googled the ECM part number on mine. It looks like the part numbers are broken down by year and model but I don't see where the transmission makes a difference.
http://www.autoecmecu.com/jeep-ecu-ecm.html

Use the Cherokee harness. I suck at wiring too and I managed to use my XJ harness. It really wasn't that hard. It looks crazy. Just do one wire at a time. The 250 or 300 can be better spent.

I just ran out and snapped this. Don't point out the rad hose, it's just a temp.
 
#165 ·
Here's a quote from sevenandeights on cjoffroad. (can I do that?)
Helpful when you're using the donor harness.




"If you can I would wait until you get the FSM. This way you can check out the wiring diagrams and the schematics that show the locations of most of the major connectors. At the very least study your current harness and maybe even take it with you for comparison.

This is from memory so don't take it as gospel:

Starting at the front driver's side . . .
1.) The harness terminates at the PCM (I would ask the yard for a "complete harness" and definitely try to get the PCM as a back-up. The front light bundle and electric fan lead are here also.

2.) Going back toward the firewall should be the diagnostic port and then some ABS stuff that hooks into the proportioning valve

3.) Next up is the firewall bulkhead connector. Definitely get this - you most likely will not use it but it helps when it comes to wiring because the pin outs are in the FSM. It allows you to test your wiring by just crimping on some female spade terminals to plug into the connector.

4.) Going along the firewall toward the passenger side will be a grommet that leads to the gauges. If the XJ is pretty torn apart you can go behind the dash and unplug the connectors and pull these wires out for completeness but you should not need any of this stuff and could cut it off.

5.) Next is the MAP sensor on the firewall.

6.) Then comes the fuel rail harness and CPS. This harness is kinda a pain to get off because it uses plastic connectors with teeth that fit over the valve cover bolts. The injectors themselves are a pain too. You will need a small flat head screw driver to pop the retaining rings off. MAKE SURE TO LABEL THE INJECTORS AS THEY COME OFF! You can disconnect the CPS unless they want to give to you (I told my yard that it was part the "complete harness" just like the PCM).

7.) I think the next thing should be the tranny wiring. My donor had an AW4 auto so there was a harness that went through the firewall to the backside of the passenger's dash where it hooked up to the auto computer (again, part of the "complete harness"). There should also be a connector for the VSS here.

8.) The next thing should be a ground at the engine block near the oil dipstick tube and a connector to the distributor.

9.) You should now be to the passenger side fender and there will be a connector to the wiper pump and maybe the cruise control and A/C. My memory is fading!

10.) AT LAST THE PDC! The PDC has been described above and will have a 6 G red wire attached to it from the battery. Right before the PDC there are a bunch of wires that go to the alternator, starter, and coil.

That's all I can remember. I think you will be safe if you cut every wire that goes through the firewall. Take your time and label everything or take pictures. I had never seen a 4.0L engine when I pulled my harness so I was pretty meticulous with the disassembly.

Don't forget the accelerator cable if you haven't got one yet."
 
#166 ·
I decided to NOT do the 4.0 head swap!

I'm probably nuts, but have decided to stay carburated. I have posted my parts for sale or trade in this forums classified section, but wanted to briefly mention it here. Hope you all don't mind. I just want this stuff to go to a more needy person. I will trade all parts needed except CPS kit for a new carburator solution. My BBD is shot, so prefer Webber. I said I would keep it brief, so there you go.
VFRPiperpilot@aol.com
432-294-3668
 
#167 ·
I'm looking at a pile of Cherokee components and trying to identify the wiring as usable. If the o2 sensor is in the header is it the earlier(Renix) system and harness?? If I'm correct the '91 and later 4.0 systems have the o2 sensor in the head pipe between the factory header and catalytic convertor. I don't want to get the wrong parts...
 
#169 ·
4.0L Swap into '84 CJ7

Just bought a 4.0 from a '99 Cherokee with 105k miles on it that I plan to swap into my '84 CJ7. Currently I'm running the 2.5L. The engine came from a Cherokee with an automatic transmission.

I'll post pictures as I rebuild it this winter and swap this spring.

I do have some questions about transmission options....

I've got the stock 4-speed manual, what are my options for easily upgrading the tranny without a lot of modifications and possibly get a 5th gear?
 
#170 ·
I've got the stock 4-speed manual, what are my options for easily upgrading the tranny without a lot of modifications and possibly get a 5th gear?
AX15. I used the one that came with the XJ donor.
 
#172 ·
Yeah, I agree that the fuel injected 4.0 beats the 4.2 anyday. My wife's 86 CJ threw a rod on the 4.2, and the shop that sent me a reman motor sent me a 4.0 instead. I bit the bullet and ripped everything I could get my hands on out of a 92 Cherokee (since there is no such thing as a totaled Wrangler!) and other than working through a few bugs, it runs better and gets much better gas mileage. Thanks for the new thread - I'll be following along as well.

Joe
 
#173 ·
Yes, the 91 and later have one O2 sensor mounted between the exhaust manifold and the converter. I believe some of the other models used two O2 sensor - one in the manifold and one in the converter.

Joe
 
#174 ·
I'm picking up my 4.0 block tommorow from the yard. Came out of a 99 Cherokee with 105k miles on it, got it for $300.

In your opinions...what is the best book to get when looking to rebuild this engine. I've rebuilt a couple of engines in the past, mostly air-cooled VW's.

I've never been a fan of the Haynes manuals.

Any advice?
 
#177 ·
I got a question about passing the smog test in California. I have an 83 CJ7 that I am planning on converting to a 4.0 head with MPFI from a 91 Cherokee. I will have all of the parts from the Cherokee. My question is what problems will I face in trying to get it to pass smog in California? I live in Nevada and they don't care, just as long as the sniffer test is OK. I searched on the California DMV web site but it was useless. Any info is appreciated. Thanks. Dustin.
 
#179 ·
OK. I tried going to their website a few days ago and it was down. I will try again. Thanks.
 
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