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Discussion Starter #1
So in the search for something better than 9-10 mpg I’m curious if my electronic choke may not be dumping more fuel than needed into my engine.

The smell of fuel is constant, but there are no leaks on the vehicle. I just replaced the fuel filter and not much has changed. I’ve read from some that the oil pressure sensor or oxygen sensors influence the electric choke or something? I’m not sure but there just doesn’t seem to be much information about it.

Now I figure that if I swapped it to a manual choke I’d conveniently sidestep and eliminate yet another possibility.

Is there any downside to running a manual choke? Seems like it’d be a sure way to conserve fuel and bypass extra circuits that just aren’t needed
 

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Your electronic choke is only active for about 1-5 minutes on startup, you can check to make sure it's working by observing its operation on cold start with the air filter top off.
The choke doesn't actually dump any constant fuel, rather controls the amount of air into the carb throat until in opens completely as it warms up.

If you have a constant fuel smell I would be looking into the vent and fuel lines at the tank if you are positive nothing is wrong under the hood.

A manual choke will do nothing more over your electric for your mileage, Fixing your current one if broken will be cheap.

If it's a rich exhaust smell, you may also want to have your catalytic converter checked, My stink went away with a new exhaust.
 

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So in the search for something better than 9-10 mpg I’m curious if my electronic choke may not be dumping more fuel than needed into my engine.

The smell of fuel is constant, but there are no leaks on the vehicle. I just replaced the fuel filter and not much has changed. I’ve read from some that the oil pressure sensor or oxygen sensors influence the electric choke or something? I’m not sure but there just doesn’t seem to be much information about it.

Now I figure that if I swapped it to a manual choke I’d conveniently sidestep and eliminate yet another possibility.

Is there any downside to running a manual choke? Seems like it’d be a sure way to conserve fuel and bypass extra circuits that just aren’t needed
It's hard to advise you since you haven't filled out your signature. What year is your Jeep and what engine do you have. It matters.

Good Luck, L.M.
 

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It's hard to advise you since you haven't filled out your signature. What year is your Jeep and what engine do you have. It matters.

Good Luck, L.M.
Apologies, I can’t quite figure out how to do that.

Nonetheless I’ve got a 89 yj, 6 cylinder, 4.2 carbureted.

I’d imagine the tank valve is in the rear by well, the fuel tank. There is a strong odor back there but I kinda figured there would be.

What about an oxygen sensor? I doubt the po had replaced that at any time. Possible ramifications of that?

It’s a small rats nest under the hook. Many of the previous electronics were either disconnected or simply neglected over time- apparently they didn’t need to pass inspection
 

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Find a post by Got it at last. In his signature there is a link to several manuals. Click on that link and then click on the manual that's close to your '89.
In the engine section look for a schematic of the vacuum system, particularly the charcoal canister. If the fuel venting system diagram isn't in the engine section it might be in the carburetor/gas tank section. It also might be in the emission section.
I'm thinking there is a rotted hose somewhere in the gas tank vent circuit and if it smells by the rear wheel well, that's the first place to look. You may need to drop the tank to find the fault. If you do have to drop the tank, post again. It's a pain to drop the tank, but with some advanced planning it can be a lot less of a chore.
If you had a bad O2 sensor, I would think the smell would be at the exhaust.

If you don't have to pass emission testing, the very best and most reliable set up on the 4.2 engine is a HEI distributor that's powered directly from the battery through a relay.
There is some debate as to which carb is the best to use with the HEI distributor. I have a Carter BBD that has the stepper motor removed. Other posters like a MC2100 or MC2150 carb and others like a Weber. The reman Carter was the least expensive way for me.

To fill out your signature, look at the top of the page, on the left, for a tab that says "user cp". Click on that tab and look at the menu on the left side of the page. Find a tab the says "edit signature". Fill in the year, engine, transmission, tire size, any mods that you know about.

You're in PA. Whatever you do, don't drive around with your doors off. You'll get a ticket.

Good Luck, L.M.
 

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Discussion Starter #6
Find a post by Got it at last. In his signature there is a link to several manuals. Click on that link and then click on the manual that's close to your '89.
In the engine section look for a schematic of the vacuum system, particularly the charcoal canister. If the fuel venting system diagram isn't in the engine section it might be in the carburetor/gas tank section. It also might be in the emission section.
I'm thinking there is a rotted hose somewhere in the gas tank vent circuit and if it smells by the rear wheel well, that's the first place to look. You may need to drop the tank to find the fault. If you do have to drop the tank, post again. It's a pain to drop the tank, but with some advanced planning it can be a lot less of a chore.
If you had a bad O2 sensor, I would think the smell would be at the exhaust.

If you don't have to pass emission testing, the very best and most reliable set up on the 4.2 engine is a HEI distributor that's powered directly from the battery through a relay.
There is some debate as to which carb is the best to use with the HEI distributor. I have a Carter BBD that has the stepper motor removed. Other posters like a MC2100 or MC2150 carb and others like a Weber. The reman Carter was the least expensive way for me.

To fill out your signature, look at the top of the page, on the left, for a tab that says "user cp". Click on that tab and look at the menu on the left side of the page. Find a tab the says "edit signature". Fill in the year, engine, transmission, tire size, any mods that you know about.

You're in PA. Whatever you do, don't drive around with your doors off. You'll get a ticket.

Good Luck, L.M.
Awesome thank you.

In regards to the pa law about doors I actually just looked it up. I’ve been driving without doors in the summer for a little over a decade with no issues.

I think it’s one of those things that’s on the books but not enforced- kinda like how we still have laws about dismantling your car when a horse and buggy pass you...😂
 

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A bad O2 sensor can affect your mileage, Raw fuel would most likely be fuel lines, Nauseating exhaust smell doesn't smell the same and points to exhaust system. On your gas tank there are two rollover valves,the supply and a return line to your tank in addition to your gas cap supply and vent lines, any and all are suspect at this point. If they have never been replaced, it's a good idea to change them all out if you are dropping your tank, once and done.

Go to the dropbox link at the bottom of my sig and pull up the 89 FSM. Around pg 500 is the fuel tank info for R&R. Then you can go to the 87-90 parts catalog and see exploded diagrams of the hoses at the tank so you will know what to expect.


Now begins the learning. The FSM is about 2100 pgs so I wouldn't suggest printing it, but there is SO much information you should familiarize with it for reference, Will also help you narrow down some of your questions to get more accurate advice.


Again as LM stated above if you are going to pull your tank, you can lower it to get a look see, without pulling the whole thing, Maybe the PO had it out recently and the hoses are all good and something is just disconnected, quick fix.

Good luck
 
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