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Drugcop4 05-14-2013 05:45 PM

1981 Iron Duke CJ5 problems/questions
I have recently purchased a CJ and have not driven it much waiting to get the windshield installed. I was able to drive it, when first purchased, for about 100 miles and really did not notice any problem with the exception of poor idling. I did notice my fuel sending unit was only showing 3/4 tank after filling it up. I drove for awhile and refilled the tank only putting in about 5.5 gallons after the drive.

I changed the plugs/wires/D cap/rotor/points after getting it back. Since that time the starter seems like the battery is near dead when starting (battery is fully charged). It is hard starting and does not idle very well, it also has a little engine "run on" when shutting it down.

Today when driving it, it ran fine until I was about 3 blocks from home. I was headed up a slight incline and it started acting like it was out of gas. I was able to limp it most of the way home before it died. I tried gassing the carb and was unable to get it started again.

I towed it to the house and when I was able to get to it about 15 minutes later it started up again. I am thinking about replacing the starter and dropping the fuel tank to see what is going on with it.

It would not surprise me that some of you have dealt with this very thing and found the problem quickly. I will take all advice I can get. I have the Rochester 2bbl carb on this motor and have not had it to mechanic yet. Please let me know your ideas to make this a reliable vehicle.

243 05-14-2013 05:59 PM

Before you start throwing more parts at it, consider some basics:

Pull the fuel line and see if you are getting flow to the pump.

Start with a fuel pressure and compression test.

Replace the fuel filter, it's cheap.

If compression is acceptable keep moving forward.

Once you have it running enough to idle, check for vacuum leaks including the throttle shafts on the carb.

If the carb leaks past the throttle shaft it will never idle well and will need a new carb.

Once it's running again without vacuum leaks, set the idle mixture with a vacuum gauge.

Drugcop4 05-14-2013 06:22 PM

243 thank you with the start to a fix. I can handle the fuel line pull and the change on the filter no problem. Much past that I don't mind admitting that I am pretty much an idiot with photos or videos to assist me. I am a "shade tree" mechanic at best. Can I "rent" some of those tools at the local auto parts chain, or is there a way to test without specifics.

I have to admit that I became a cop because a lack of other skills so any basic info you have is appreciated. Heading outside now to pull fuel line...

243 05-14-2013 07:09 PM

I am pretty sure you can rent the compression gauge from the parts store, possibly the vacuum gauge too.

I am sure you can find videos on youtube, all of these checks are pretty easy and seeing them in a video will help you a lot.

Hang tight, I know there are some JF member in IL that may be close enough to help out.

I got ahead of myself too, do you know the history of the engine?

Drugcop4 05-14-2013 08:09 PM

Checked the fuel filter it seems clean, took it off and blew into it no gunk. I will change it to a clear filter tommorrow (it is metal). I started back up and poked and prodded. I found the idle screw and advanced the idle some. It ran without stalling at about 1100 to 1150 rpm for about 20 minutes. It was rough and jumped around alot. I hear what sounds like sucking wind but cannot find a hose or orifice that is not plugged.

The previous owner is mechanically inclined but there is a manual throttle and choke cable that I don't think are factory. There is a plug on what I think would be called a vacuum advance that has no wire on it. I see one loose but I am afraid to hook it to it.

It would not shock me that the carb needs pulled/cleaned/rebuilt. Or would I be better just getting a new one. What are my options other than the Rochester varijet II?

243 05-15-2013 04:54 AM

The red wire might be for the electric choke.

If you can rent or buy a vacuum gauge that may be the best place to start. Find a constant vacuum port on the base of the carb and plug in the gauge, if the motor is pulling less than about 18 hG there is a leak or the idle mixture is out of adjustment. Be sure to check the power brake vacuum if you have it and also the PCV hose.

Once you have the gauge screw the idle mixture screws in until they are lightly seated and back them out 1.5 turns. With it running adjust one screw out slow and to the highest vacuum reading and then turn it in about 1/8 turn. Adjust the other and then back again one more time.

Idle mixture screws are at 12 and 1 on this carb.

I bought a NOS 2SE from robbob36 and he still has them listed. One advantage of NOS over rebuilt is you are almost guaranteed tight throttle shafts.


caseypotts 05-15-2013 07:32 AM


There is a filter inside the carb as well, or at least there should be that might be cloged. It is located where the fuel line enters the carb. When you unscrew it the filter will come out and there is a spring behind it. When you put a new one back in make sure you put it in the correct way (hole pointing towards you) and make sure that you remove the old gasket.

I would replace that metal filter with a clear plastic one so that you can see what is going on.

Drugcop4 05-15-2013 09:46 AM


Originally Posted by caseypotts (Post 15435009)

There is a filter inside the carb as well, or at least there should be that might be cloged. It is located where the fuel line enters the carb. When you unscrew it the filter will come out and there is a spring behind it. .

Is this the type that jumps out at you? I have bids in on a rebuilt carb on ebay. I am also going to go ahead and replace the starter. Is there any chance that timing could come into play here. I have had some engine run on and "dieseling". Is it time to take this one to a mechanic and let them deal with it?

caseypotts 05-15-2013 12:57 PM

Not that much spring!
I don't think it is time to pa
y someone yet

gary c 05-15-2013 02:13 PM

Those are all good points and should be checked out. After you get every thing checked, than check your timing. There should be a sticker in front of the radiator on the shroud that gives your timing numbers. Good luck, the engine is weak on power but is fun to drive.

Drugcop4 05-15-2013 08:44 PM

I changed the filter to a clear one and it would appear that the filter does not fill heavily however the fuel looks clean. I checked for the screen and spring and there is not one. I noted that the "manual" choke wire was attached to an area that I did not think would actuate the choke. I poked and pulled and ended up with a couple of arms off of the choke set that I probably should not have taken off.

I started the motor and let it run for quite a while. I adjusted the idle to about 1k and it seemed to run better. I also let it run and it maintained quite well. After running awhile I turned the key off and it ran on for a bit. I have to admit that I have no clue how to adjust the timing. If I remember shop class right that would be turning the distributor to adjust it. The location of the distributor makes that look really hard.

I have found a carb on ebay that I think I can get for about $50 and they are calling it a professional rebuild. I think I am going to get it and try to find someone to put it on. I am afraid if I do it the poor jeep will never run again.

caseypotts 05-16-2013 06:59 AM

Having a complete carb will help. I've gone both ways on my choke. Electric sure is more convenient but every few years you will find yourself having to deal with it. I'm back to electric now.

gary c 05-16-2013 06:39 PM

To ajust the timing, I've found the best way is to get under the Jeep on the passenger side so you can see the hold down bolt. Loosen it enough to move, than get back up top and set per specs or runs the best, than tighten from below.

Drugcop4 05-16-2013 08:30 PM

Is there any chance you or anyone else would have a photo of the set screw and location. Or a link where this is shown.

I drove the Jeep for about 30 to 45 minutes to night and it ran great the whole time. I stopped by a store for a short time and when I can out it did not want to start. I tried a little starter fluid and no go. I waited about 5 minutes and finally got it started. Every time I shut the Jeep off it had bad engine run on.

notlost 05-16-2013 09:40 PM

Engine run on can be caused by an excessivley lean mixture. If you don't have a vacuume guage, try running one mixture screw in just until you hear a drop in RPM. Then back it out until RPM is regained, plus half a turn. Do the other side the same way. You man have a vacuume leak also. Try spraying carb cleaner around the base of the carburetor and vacuume lines. if you hear a rise in RPM, you know you have a vacuume leak.
I had the Iron duke in my CJ5 but it had been upgraded with a holley 5200 before I got it. Even running good the're under powered. The best part Of the Iron duke set up is the bellhousing. They have the chevrolet 90 degree pattern on the engine side and the ford "butterfly" pattern on the transmission side.

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