Converting from Fuel Injected to Carbureted

[GosaGT1988]

What all is necessary/needed to do it on a 4.0L in a 1990 Pioneer with the Renix system?

[Pete M]

Before all the vultures pounce on you, be prepared to hear over and over how silly that idea is. :D

 

But seriously, why are you contemplating this? What's wrong with the system as it sits now?

[GosaGT1988]

There's nothing wrong with it, I was just wondering. I am however trying to figure out a way to bypass that computer in there.

[Pete M]

Why? :hmm: I'm incredibly puzzled.

[GosaGT1988]

I have never been a fan of ECUs. The one in my 89 YJ has been bypassed completely by the previous owner and I have no idea how they did it. The difference is that one has a carburator.

[Pete M]

That computer and those injectors are precisely why your truck rocks (well, them and the solid front axle).

 

But I imagine if you were to want less reliability, less performance and worse fuel mileage, I bet somehow you could adapt the carb from a 4.2L Wrangler. But to make that work I bet you'd also have to swap to the YJ's head and manifold. This should be relatively easy to find since YJ owners are dumping them for the better flowing and superior fuel injection setups found in your truck and later Wranglers. Heck, you might even be able to trade your stuff for some YJ owners stuff. :D

 

But seriously, the computer in our trucks has a long history of reliability and a proven track record of performance. It should never cause you grief. :thumbsup: :cheers:

[JeepcoMJ]

agreed with pete.

 

you won't bypass the ECU on the renix system, as the injectors won't be timed properly then.

 

what's your beef with ECU's? an ECU is usually the strong link in the system...in a renix 4.0 system, the first thing to cause issues is the mass of sensors (hence the lack of some of them on the HO system)

[HOrnbrod]

If you are contemplating doing this to make your engine less complicated and/or for better fuel mileage you will be going from the frying pan into the fire. While our rigs are not well known for their incredible mileage, they are known for their relative ease of maintenance and reliability. Swapping out the ECU and FI system for a carbed engine is a giant step backwards IMNSHO. :cheers:

[Eagle]

I can think of one very good reason to retro-fit with a carb: being able to limp home if your fuel pump goes out, or the CPS (which, of course, you won't have with a carburetted engine). I have considered this many times, but I can't do it because it won't pass emissions. (Not meaning it would run dirty, just that it's not a legal conversion. I'd fail on a vial equipment check.) If I were building a Jeep specifically for going on long treks into far away places (like Africa, or Patagonia in South America, or the Atacama desert in northern Chile) I would do it for sure.

 

With a carburetor, you only need a couple of psi to deliver fuel to the float bowl. On my old Hudson pickup (yes, Hudson did build pickups, and I've owned three of them) I have limped home using a coffee can suspended under the hood with a rubber hose to act as an intravenous feed to the carb when the fuel pump crapped out. Try THAT with MPFI that needs 39 psi to run.

 

I am also quite certain I could rig a 4.0L with a carb to get better gas mileage than the EFI models get. My old Rambler American used to regularly post 28 MPG highway. I've only gotten that ONCE with the '88 Cherokee, and I've never come close with the MJ.

 

-------------------------------

 

How to do it:

 

Hit the junkyards and get the manifolds, distributor, coil, etc from any 6-cylinder AMC car, preferably a 258 (4.2L) but a 232 or even a 199 will work. The old 199 only had a single barrel carb, though. The best setup would be an aftermarket intake (probably Clifford offers one) to accept a small 4-barrel carb. Otherwise, just go with the standard 2-bbl that came on the 232 and 258 engines.

[jeepthing07]

http://www.cliffordperformance.net/Merc ... _Code=J258

[Eagle]

^^^

 

That's a nice manifold, but it doesn't fit the 1990 Renix engine.

 

BTW, whatever you do, do not be tempted to use the carb from a 4.2L Wrangler. It's not only a lousy carb, it's also dangerous. A lot of Wranglers burned up because of that carb. If I were doing it, I'd use a 400 cfm version of the old Carter AFB. Edelbrock now makes that carburetor, although I don't know if they go that small. It's very reliable, easy to tune with replaceable jets and metering rods, and the small primaries generate excellent gas mileage as long as you keep your foot light enough to not open the secondaries.

[pingpong]

I suppose you could accomplish this by using a GM HEI ignition off of a stright six.... some modding needed. Use some form of aftermarket intake, and carb. While not a swap I would do.. I could see the benefit, if as Eagle said you were In a third world location with no stores around

[Pete M]

I could see the benefit, if as Eagle said you were In a third world location with no stores around

 

Like Florida? :dunno:

 

 

 

:D

[Eagle]

I suppose you could accomplish this by using a GM HEI ignition off of a stright six.... some modding needed. Use some form of aftermarket intake, and carb. While not a swap I would do.. I could see the benefit, if as Eagle said you were In a third world location with no stores around

Why mod a GM? Jeep was using a high-energy ignition for years with their carbureted engine. Just get the ignition out of any 2.4L Wrangler or any AMC car with the 232 or 258 in-line six. All you need is the distributor and coil, I think. I don't remember there being any supplemental "ignition module".

[GosaGT1988]

Florida might as well be a third world country. The stores around here are crap. The only place worth going to is either Wilson's 4X4 or Jeep Toy Box but they're a little more expensive than what I can afford.