98' XJ 4.0 carb conversion
 

I have a 98' XJ that has had electrical gremlins in the interior wiring for years. I also have a lack of power and mpg compared to when I first bought it. I have had it into several reputable mechanics and even had the computer reflashed a couple of months ago with no luck. Because I have so much invested in suspension, steering, axles, brand new tires and misc new parts when I decided to move from AZ to MT I loaded the Jeep on a trailer and drug it up here. When I backed it off the trailer I could smell a hot electrical short. Well now it kills the battery in hours and you can pull all the relays and fuses out of the engine control box under the hood and various spots on the motor (CC module, fuel pump and a wonderful buzzing from the bottom side of the fuse box) still have power! :cursing::cry::brickwall::help:

So after letting it sit for a couple of months not wanting to take a loss on all the parts and really not wanting to swap out the whole wiring harness. I am beginning to wonder if I can clear out a bunch of sensors and wires on the engine and convert it to a carb setup. I don't have to worry about emissions/inspections up here so that is no problem. I have read about using a 4.2 intake, Holley or Weber carb, fuel pressure regulator (5psi?) and HEI distributor. Would I need anything else?

Also would the AW4 and gauges (speed, tach, temp, oil pressure) still work if I pull the FI system? Obviously I would leave the above sensors on the motor.

98' XJ 4.0 carb conversion
 

It would probably be cheaper and easier to buy another jeep and swap the suspension and any other mods over.

With it being odb2 i don't think a lot of things will work with out the ecm running them.

I have a 98 I am getting ready to scrap. Let me know if you want the harness.

A harness/wiring swap or a complete swap of what you have to another XJ with OBDII would be a much better choice. FI is so much better than a carb on a 4x4 off road its unreal owned a lot of them over the years and I remember all to well. In fact when I lived in Butte I would have loved to have had a FI engine over that 53 Willys Wagon and fooling with the carb lol.

This was actually the original decision. Find a clean XJ with a 5 spd and manual windows and locks to swap over to. Just haven't had any luck finding one.

I have a little 87' Samurai that is carbed and the idea popped into my mind. I love how simple that thing is. Both the Samurai and a Honda NX250 (carb) start quicker than any of my FI vehicles/new motorcycles at any temp/elevation I have been in down to about -2.

As far as FI being better... I am a fairly strong proponent of mechanical things... carbs. True FI will self adjust for elevation and temp. But if you know what you are doing with a carb it can run just as well as FI. It just takes more attention to keep it in optimum tune. Plus I just like fewer parts and simple when possible. But that is the important thing (when possible)

Thanks for the input everyone.

Hey man! Just south of you- check out Wild Bill OHV area sometime if you haven't... its a good time. (From Kila-Lakeside)

As for your question, I agree with the others. It would be a ton of work for very little (If any) gain. Also worth mentioning that some of the trails in our neck of the woods have serious elevation gains. Some of the carbed guys I run with have problems due to that. I also have a mostly clean 5-speed, manual window XJ I might be selling :)

Thanks for the heads up. I'll have to go take a look. PM sent.

Fixing the wiring problem is gonna be easier than converting it to carb.

Did not get your PM but here is my album from multiple trips to the area- cool because there is a bypass around everything real challenging so if you don't feel up to it, just go around.
https://www.cherokeeforum.com/g/album/3236259

Two clubs in your area are the ones responsible for building it and it is still a work in progress. I can give you their info if you like.

Trail is only like 20 min from you!

Flood recovery vehicle?

I have saw a boat load of those going through the salvage auction here and going out by the semi truck load to dealers all over the states. We have several large insurance salvage pools in this area that serves 5 states last auction over 500 units and a lot of water damaged ones.

I am the second owner, and until I brought it to MT it has always been an AZ vehicle. No flood damage. But it was involved in a front end accident 4 years before I bought it and it took Carfax 10 years to report. I just learned about the accident a few months ago.

These are the same reasons everyone gives when they don't understand how fuel injection actually works and/or are afraid of it. I mean, almost to the letter these are the same excuses used every time. I used to be a "carbs are just as good" guy myself, so I'm intimately familiar with resisting the technology. Honestly, what I really meant was "I understand carbs and am unfamiliar with fuel injection's workings, so I'm making excuses to avoid it."

I submit that injection is fewer parts than a carb when you consider all the parts that go into assembling the carburetor itself, it is easily superior in performance, and it is much simpler to maintain. There's no fiddly tuning necessary at all; I never have to adjust my idle speed, idle mixture, high speed mixture, choke... nothing. Very rarely a sensor that is either directly or indirectly related to the injection system might crap out, but it's generally quite easy to know which sensor is the culprit and clean or replace it.

Tracking down the short would be easier than converting an OBDII injected engine to carb. (note: the fuse/relay block in the engine compartment isn't the only fuse block on the vehicle). Block off some time so that you can patiently peruse the vehicle with a volt meter, and find that short. Even if you have to swap the whole harness, that's still easier than a proper carb conversion, and I can't imagine how that should be necessary.

I will attempt not to be insulted by your initial statement and look only at your comparison. I am completely familiar with how FI works and carbs. I was raised by an SAE mechanic that was on an F1 pit crew for a season back in the 80's. I was simply looking for a second opinion on this particular vehicles conversion. I am not in the least bit affraid of digging into and removing the FI off the engine. It's the fact that I have the AW4 trans (computer controlled) and that the gauges are also computer controlled, that left me wondering if the conversion would not be worth the struggle of making them work.

As for the carb having more moving parts I would say you are splitting hairs. A basic Weber, Holley, Edelbrock carb has many fewer parts than an overly engineered factory carb from most any manufacturer. Plus the fact that most any FI system has several sensors (coolant temp, ambient air, air charge, CPS, MAP or MAF, TPS, O2, speed... just to name a few), a throttle body which has some of the same moving parts as a carb, idle air valves, fuel injects (also full of parts), the computer (if not 2 or more) plus the miles of wires, harnesses and connectors to link them all together along with other systems on the engine (ignition, braking, transmission) I think the argument that a carb has more parts to it quickly disappears.

I do agree and already stated that a carb takes more attention. Easily done at each oil change or a couple of minutes on the side of the trail if elevation gain is to much. I also agree that a properly functioning FI system makes life easier and usually gives more consistent power, cleaner emissions and potentially better fuel economy. However I have owned well over 20 vehicles with a mix of carbs and different generations of FI and I have had far less problems with carbs than I have had with most of my FI vehicles. I also have never had any vehicle with a carb leave me on the side of the road because I could not do at least a temporary repair to get me down the road. I have had on more than 1 occasion a FI vehicle decide to cut out for no apparent reason and had to be towed because of a sensor that failed. Sorry but I don't carry a selection of resistors, soldiering iron and a list of each sensors optimum resistance to trick the computer into letting me limp down the road.

FI is better than a carb on inclines and at altitude.... This is correct. FI was originally invented so that piston driven fighter planes could fly at higher altitudes (usually assisted by turbos) and upside down without the engine stalling. In fact dry sump engines also came from this same thing. Since FI would allow the plane to do a roll and the oil in the pan would quickly flood the engine. However I do not own a rock crawler and will not and have not needed the ability to play Spider Man with this XJ. I have taken a carb from Phoenix, AZ at 1300 feet to the top of Pikes Peak, CO 14,110 feet in a 2 day period with a carb and never had to adjust it. Did I loose more HP than if it was fuel injected? Yes. Did it still do it without noticeable issues? Yes.

If you look at an old bare bones carbed engine, take your pick Jeep (Willy's, Kaiser, AMC) Ford, Chevy, Dodge, International...) it is very simple to see what is going on and what it is you are looking at. Engine, Carb, Distributor, Fan, Radiator, Battery, Alt and belt. Nothing else is need to make it work, making it easier to reach what you need to repair it. Many modern FI engines are great when running properly, but when they do act up you have to work around and in a birds nest of wires, vacuum lines and hoses to get to what you need to repair. In some cases even removing other components to reach the needed repair. The idea of simplifying the 4.0 in the newer XJ body sounded like an interesting prospect so I was simply looking further into it. I have decided to fall back to my original plan of swapping my parts to a different XJ when I find the right one.

Finally tracking down the short is not easier. I have had this XJ into 4 different reputable mechanics in the Phoenix, AZ area, costing me over $1000 not to mention that I had the computer re-flashed just 2-3 months ago and the countless hours I have spent chasing wires myself. I can assure you, that much time, money and effort put into a single problem on any vehicle would be enough to frustrate anyone.

Again thanks to everyone that has replied. You have all helped me with this idea.