Bad Gas milage in my CJ7 -

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post #1 of 5 Old 04-29-2004, 12:43 PM Thread Starter
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Bad Gas milage in my CJ7

I recently pruchased a 1984 CJ7 so i am new to the jeep world. The Jeep runs great and does not seem to have any problems except that I get about 7-8 miles per gallon. It has the 6 clyinder 258 in it and I was very shocked it was guzzeling so much gas. It does have 35 inch tires on it with the stock grears. I am assuming that is contributing to the problem. I was also wondering if it could be a carberator problem. I was considering trying to throw on a mc 2100, but I am really not a mechanic and kinda worried about messing something up. Does any body have any suggestions or recomendations?

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post #2 of 5 Old 04-29-2004, 02:25 PM
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1982 CJ7 
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Location: Alabama
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My suggestion is:

Do it.

or go with the Weber kit. Either one is tons better than the stock carter carb. As for the gas mileage, that might help, but probably isn't the only problem.

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post #3 of 5 Old 04-29-2004, 04:04 PM
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1981 CJ7 
Join Date: Jan 2004
Location: Valley Forge, PA
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You can try tinkering with the mixture on the carb. I had my Carter carb replaced a long time ago (with what, I actually have no idea -- that's a long story) and my mileage dropped from 16 or 17 mpg to 5. The garage (a Jeep dealership, no less) refused to do anything about it. Skipping a lot of the detail here, I finally got a refund for the work they did and then adjusted it myself. Mileage went right back up where it had been, and has more or less stayed there since.

'81 CJ-7, 175,000 miles
Stock 258, SR-4
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post #4 of 5 Old 04-29-2004, 04:29 PM
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Holy that sucks. I just figured mine and I got 15mpg in the city! I run 33"s and the stock 3.31 gears. I would look at a serious tun up. Keep in mind that the speedometer may not have been corrected when the lift and tires were done. that will make a big (maybe) difference.

Just figured it out, stock 225/75/15 to a 35" tire will decrese the readng on your odometer by quite a bit. 21" per tire revolution. This works out to an increse in actual distence of 1.23. If you multiply the 7-8 you have you get 8.5 to almost 10mpg. Thats still not great but sounds better.

As mentioned before, play with setting on the carb. Could be way off.

2000 Cherokee
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post #5 of 5 Old 04-30-2004, 06:47 PM
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rebuild or get a new one

I rebuilt my BBD carb a long time ago (it's gone now, Howell TBI) and it's pretty straight forward if you can follow instructions, have some end wrenches, and label vac connections. When I did mine, I was pretty nervous since it was my daily driver and I flunked the carb class in my small engine course in high school. It did run better, but that BBD carb is pretty notorious for problems.

My suggestion to this, plug ALL vac connections except for the one the distributor. All those vac components on my 84 were the root of my crummy mileage due to vacuum leaks. Made a world of difference for me. Still passed smog too, with flying colors....had to fake the setup by putting vac plugs on all but the dist vac port then put larger size vac tubes over the top of them to hide it for the underhood inspection....which it passed...after I put a fresh air intake tube on.

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