Choke adjustment help please. - JeepForum.com
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post #1 of 17 Old 12-14-2008, 03:29 PM Thread Starter
dsfordguy
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Choke adjustment help please.

Hey guys I have a 73 cj5 with 258 and 1bbl carter yf. I just rebuilt the carb yesterday and that solved my problem with it not staying running unless i close the choke by hand. Now it runs but i dont think the choke is working, When i first started it it smelled like it was running rich and the fast idle never kicked on. Also the choke cover has no index mark or anything on it to line up with the marks on the air horn casting. Could anyone tell me how I can adjust the choke and fast idle correctly?

Also, with the timing at about 5 btdc I can only get the engine to rev to about 3500 rpms or maybe less before it sounds like its about as far as it can go. Don't these engines rev to 4400 or so? When i drive it up to about 55mph it sounds like its pinging also. If this helps i am using an aftermarket hei dist. with the plugs gapped at .055 I believe. Does anyone know what would cause this?

Thank you for your help


Last edited by dsfordguy; 12-14-2008 at 03:45 PM.
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post #2 of 17 Old 12-14-2008, 03:58 PM
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I would close the plugs down to around .045 to start with, at higher RPM's you might not have enough energy in plugs to jump .055. Yes the engine should be able to rev higher, but it could be a number of issues including timing and/or fuel starvation but try the plugs first. The fast idle cam can be adjusted by bending linkage. When the engine is cold, crack the throttle to close the choke plate. Look at the fast idle cam to see if it's making contact with the screw on the throttle bracket. The best thing to do is look up this info on google or get the shop manual out and go step by step. There are specific clearances that you should shoot for.

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post #3 of 17 Old 12-14-2008, 04:59 PM Thread Starter
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Thanks for the reply. I will try gapping them to .045 and report back what happens. I will also search the fast idle cam and choke stuff. I would really like to get this thing up and running the way it should.

Thanks
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post #4 of 17 Old 12-15-2008, 07:42 AM
Mike Romain
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The Haynes CJ manual has very good directions for setting up the carbs. It is also very good for wiring.

Mike
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post #5 of 17 Old 12-16-2008, 05:50 PM Thread Starter
dsfordguy
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I gapped the plugs to .045 and it still wont rev any higher than 3500 rpms. What else could it be?

When I first start the engine it seems like its running rich cuz there is black smoke and the engine wont idle very well and dies sometimes. It also sputters when i give it gas. It is like this for a while then it stops. Also I have an inline fuel pressure guage installed and when the engine is running I have between 5 and 6 psi but when I turn the engine off the pressure bleeds off. Does this mean the float is sticking? The float wasn't full of fuel when i rebuilt. I checked the float adjustments when i rebuilt the carb and they were good. I also replaced the needle and seat assembly. Could this have anything to do with the metering rod adjustment? What should I do?

Another thing is that I think I may have found what i thought was pinging. I think the cooling fan is contacting the lower radiator hose when under load because when I replaced a power steering hose I moved the radiator up one inch because it was resting on the old power steering line and cracked it from vibrations. What should I do to solve this? The radiator is just about resting on the power steering lines going to the steering box even with it relocated one inch up. Also the fan I have is one of those flex fans.

Thank you for your help.
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post #6 of 17 Old 12-17-2008, 07:27 AM
Mike Romain
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I have the 2BBL carb and intake on my 258 and set my timing to about 9 deg BTDC with 91 octane fuel. Mine will rev to 4400 rpm in 2nd @52 mph.

Mike
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post #7 of 17 Old 12-17-2008, 11:02 AM Thread Starter
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Do I need to advance my timing a little more?
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post #8 of 17 Old 12-17-2008, 11:23 AM
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Quote:
Originally Posted by dsfordguy View Post
Do I need to advance my timing a little more?
I think I would. You can also fine tune the timing with a vacuum gauge. You advance it until you get the highest manifold vacuum, then you back it off about 1" of vacuum on the gauge. This should be real close to optimal for your engine.

Most of the 2BBL ones run nice at 8 or 9 BTDC, some even higher.

I have noticed my Haynes manual calls for 3 BTDC on a 73 and 74, so maybe you need to go the other way?

Mike
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post #9 of 17 Old 12-20-2008, 09:36 PM Thread Starter
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I set the timing to 3btdc and I think it is no longer pinging at 55. I still cant seem to get any more than 3500 rpms out of the 258. What else could it be? The chilton's manual says something about some tachometers don't work with hei. Do you think my tach is wrong? Its about 6 months old. According to the tag on the rear axle I think i have the 3.73s still and 31" BFG MTs and when I punch the throttle I shift to 2nd gear at about 25 on the speedo which may be between 25 and 30 because of the 31's. Does this sound right? O ya I think it is the stock 3speed tranny also.

I think i fixed the problem with it seeming like it was flooding. It was leaking around the carb baseplate. Now I can see if I have the choke adjusted right in the morning.

Thanks
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post #10 of 17 Old 12-20-2008, 10:11 PM
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My 76 with a YF runs with 8*-9* of timing. But I don't know the combustion ratio and other stuff that might make setting it at 3* desirable. It's certainly not the carb that would make it have to be that low.

Did you set the mixture correctly on the YF. Particularly the part where you have to push down on the accelerator pump and adjust the mixture screw. If this is not done correctly you will run to lean and ping and not get very high in the RPM range.

It's all covered in the Haynes manual and did not see what they were trying to do the first time I read it so it's easy to get confused.

Stock Tachs do work with the HEI but did you perhaps put an 8 Cylinder tach in there? That means your actually turning 5250 RPM with a 6cylinder.

The YF can have a leak that looks like it's around the base plate if the level is to high. It will leak out the well for the accelerator pump. Make sure your float is set correctly. Of course a loos base plate will also leak allowing air in and leaning out the mixture causing it to ping and yada yada....


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post #11 of 17 Old 12-21-2008, 12:13 AM Thread Starter
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I believe it was air that was leaking around the base plate. But I may still have fuel leaking from the gasket between the throttle body and main body or somewhere near there. Would this mean the fuel bowl is overfilling? My carb did not have a screen with the needle assembly like in the manual neither did the rebuild kit. Could this be a problem also?

I adjusted the screw on the metering rod while holding the accelerator pump like it said in the chilton's manual. Was I supposed to do something with the air fuel mixture screw also? Another question, When the throttle flap is closed all the way does it sit totally horizontal or does it have a slight angle? I think mine had a slight angle.

Also the tach I installed is for a 4,6, or 8 cylinder engine. It has a switch. I made sure I put it on 6 before I installed it.

Thanks
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post #12 of 17 Old 12-21-2008, 06:08 AM
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If it leaks around the gasket between the throttle plate and the body it just means that it's not seated and tight for some reason. (Loose screw, dirt, old gasket left over.?

There are a lot of reasons for the fuel level to be too high. Sticking on the side of the bowl, float has fuel in it or soaked with fuel. Top twisted a little, hinge worn out on the float...

Screen should not cause a problem right now but it might let dirt in causing problems.

THe idle mixture is later when your tuning it on the engine. If the idle mixture has no effect you either have a vacuum leak or the idle RPM is to high.

It should have a slight angle to it but not too much. It woul cause it to idle to high.


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post #13 of 17 Old 12-21-2008, 10:15 AM Thread Starter
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According to my tach the idle was at about 600 rpms. Shouldn't the motor die if I screw the mixture screw in all the way? It keeps running but you can hear the idle go down a little.

What I did to adjust the metering rod was hold the accelerator pump down and loosen the screw till it lifted off the metal piece it touches then I screwed it to where it was just starting to touch it. Then I tightened it one more turn. Is this correct?

Also when I spray carb cleaner at the outside of the throttle shaft where it goes into the carb it bogs down a little bit. I must have a vaccuum leak there. Does this mean I need a new carb??

Last edited by dsfordguy; 12-21-2008 at 10:39 AM.
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post #14 of 17 Old 12-21-2008, 12:40 PM
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It should kill the motor if it goes in all the way. Usually it indicates the throttle is open to far probably compensating for another problem. Usually a vacuum leak

That sounds right but my book are away for Christmas cleanup.

Sounds like the bore for the throttle shaft is worn out. It can bind the throttle and do other bad stuff.
You can get it fixed if you absolutely need the carb but a new one is easier to find than a place that puts in a new bushing into the base.

Think about switching to a newer manifold and 2 bbl carb maybe Something like a MC2100


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post #15 of 17 Old 12-21-2008, 06:55 PM Thread Starter
dsfordguy
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Could the vacuum leak at the throttle shaft be causing me to have pinging at 8 degrees advanced? Could it also be the cause of it only reaching 3500rpms?

Thanks
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