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TBI to Carb ?'s


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'84-'85 Cherokees with the 2.5 were carb'd. Not sure if it's a direct bolt-on to the TBI intake, though.

 

Also, carb versions used a different computer, coil, had a vacuum advance on the distributor, and a mechanical fuel pump on the block. And a much bigger rat's nest of vacuum hoses. If you found a good donor XJ at the junkyard, then maybe you could get all that stuff cheaply? :dunno:

 

IMHO, for all the time/trouble/$$$ involved in a carb swap, I'd think you could just replace every single part on the current TBI setup.

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'84-'85 Cherokees with the 2.5 were carb'd. Not sure if it's a direct bolt-on to the TBI intake, though.

 

Also, carb versions used a different computer, coil, had a vacuum advance on the distributor, and a mechanical fuel pump on the block. And a much bigger rat's nest of vacuum hoses. If you found a good donor XJ at the junkyard, then maybe you could get all that stuff cheaply? :dunno:

 

IMHO, for all the time/trouble/$$$ involved in a carb swap, I'd think you could just replace every single part on the current TBI setup.

 

you can't put a normal Carb on it ? it has to be the factory unit ?

 

Mike

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you can't put a normal Carb on it ? it has to be the factory unit ?

 

Not sure what you mean by normal carb? A factory unit is a normal carb - it was a little one-barrel unit. You can get reman'd ones at NAPA for 300 bucks.

 

What I'm saying is that even after bolting on the carb, you'd still have to worry about fuel and spark. The TBI uses a higher pressure fuel pump, the ICU under the coil uses signals from the sensors & ECU to determine ignition advance/retard, etc. AFAIK, none of those systems are compatible with a carb. So, if you switched to a carb, you'd have abandon all the existing electronics, plumb in a low-pressure fuel pump, put in a distributor that had a vacuum advance, new coil, and some way to control spark.

 

Can it be done? Sure. Anything's possible. But I'd think that for the same cost as putting together a carb system, you could probably replace every possible trouble spot left on your TBI set up. Just my .02.

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It's pricey, but you can buy carburetor setups for the 2.5L. Whatever you do, do NOT try to use the factory carburetor. It's partially computer controlled, and it's a horror. I haven't done it, but I see no reason whatsoever that you can't swap the throttle body for a carburetor and retain the existing ignition system. It'll just be sending a signal to a dead circuit for the injector -- so what?

 

Rusty's used to sell the carb conversion. I don't trust Rusty's springs and track bars, but the carburetor is from a reputable company and Rusty just sells it, and the reports have all been good.

 

Also, Google "Nutter bypass."

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Yup this was a pointless thread !

 

You guys already got me confused and pissed cause I have no idea what any of this means.

 

Let's stay simple here.

 

I want pull the TB off throw it in the trash can.

 

Then drop on a carb.

 

Then rip out the dist n toss that away.

 

Then drop in vac dist.

 

Set the timing.

 

Rip out the fuel pump wires.

 

Remove the plate install the mech pump.

 

run a line tank to pump.

 

Run line from pump to carb.

 

Prime and drive.

 

If it is not that simple it is then beyond my comprehension and won't be done.

 

Mike

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Yup this was a pointless thread !

 

You guys already got me confused and pissed cause I have no idea what any of this means.

 

Let's stay simple here.

 

I want pull the TB off throw it in the trash can.

 

Then drop on a carb.

 

Then rip out the dist n toss that away.

 

Then drop in vac dist.

 

Set the timing.

 

Rip out the fuel pump wires.

 

Remove the plate install the mech pump.

 

run a line tank to pump.

 

Run line from pump to carb.

 

Prime and drive.

 

If it is not that simple it is then beyond my comprehension and won't be done.

 

Mike

 

 

 

YES!!! it is just that simple. almost all cars and truck built before 1985, are now know as B.C. (before computers) and the junk yards are full of them. so finding every thing you need should be easy. basically the motors have not changed much over the years, they just have added bunch more sensors

 

you can even get a electrical in line fuel pump that works with a carb. I know this because I have one on my 86 XJ

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Throwing parts at vehicles is never the best way to fix anything. And trying to get help from us by saying you are going to crush your MJ because YOU are unable to fix it, or saying you should have bought an S-10. I will give you one last post.

You say that when you push in the EGR diaphram when the engine is running has no effect? It should stall because you are leaning out the mixture significantly. It could be that it is bleeding by already and the computer is richening up the mixture as much as possible, but when you need more fuel it can't keep up and the truck stumbles.

 

Or, you have bad gas or somehow managed to put E85 in it. I think someone mentioned bad gas before.

 

The picture of the plugs appear to show then burning OK, maybe lean, definitly not rich.

 

Fuel injector COULD be bad. Has it been tested? I believe someone here offered to loan you one. There is also a pressure regulator inside the TB that could be bad.Or you could grab a TB with injector and regulator from a JY and bolt it on.

 

Just because you installed a bunch of new parts does not mean they are working properly.

 

There is a scan tool for your truck. DRB II

 

Now, feel free to contiunue insulting us and our trucks.

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You guys already got me confused and pissed cause I have no idea what any of this means.

All of the posts provided pretty specific information that was directly responsive to your question. If you don't understand what any of it means, with all due respect how can you possibly expect to do anything with the vehicle?

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This sounds like something I'd do, if for no other reason than just for the heck of it. I would leave the fuel pump in the tank and install a inline regulator with the return line between the reg and and carb just to help prevent vapor lock. Just my .02 worth. Frankly I think it can be done, TBI to carb, I just don't think it would be worth it.

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I have also thought about the fact that a carburetor makes a lot more sense for a serious trekking vehicle. With EFI (throttle body or multi-port), if you're way out in the boonies and you lose the fuel pump or injection, you're basically toast. In the past, I have hooked up a drip can under the hood to provide gravity feed for a carburetor and been able to drive the vehicle several miles to get back to home base. I'd like to try it just to say I did it ... what holds me back is that Connecticut has mandatory emissions inspections, and I don't think a retrofit of an EFI vehicle to carburetor would pass emissions.

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