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Unread 10-02-2013, 01:03 PM   #1
teedubbaya
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Weber 32/36 on a 258 will only run rich

From a different thread:
Quote:
Originally Posted by uptillnow View Post
The "typical" jetting below 3800 feet is this:
Primary Idle .75mm
Secondary Idle .60mm
Both Mains 1.40mm (or, P 1.40mm S 1.45mm)
Primary Air Correction jet 1.70mm
Secondary Air Correction jet 1.60mm
I know this has been discussed ad nauseum, but I'm not finding rich idle discussions where the idle mix and idle speed screws are cranked all the way in just to make it run.
I live at 3600 ft and was thinking I need way leaner jets, but then ran across the above specs posted by uptillnow.
I have this same carb jet setup (1.45mm mains) on a recently acquired CJ7 (258) and the only way I can get it to stay running is to turn the idle mix all the way in (CW), and have the idle speed screw turned all the way in (CW). It runs, but idles super-rich and is a gas hog.
I've followed the initial setup from the "Weber setup and tune discussion"
http://www.jeepforum.com/forum/f8/we...ssion-1051137/, but it won't even start when I'm at that baseline setting.
It has new fuel filter, and a Holley 4psi FPR (idle pressure actually shows less than 3psi).
Any advice on where to go next, if those jets are correct for my elevation?
Thanks!

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Unread 10-02-2013, 01:45 PM   #2
Matt1981CJ7
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Take the FPR off and see what it does.

Was the engine running OK before you switched carbs?

Matt
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Unread 10-02-2013, 02:09 PM   #3
swatson454
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Why don't you pull that idle jet out and see what size it is. And I agree with getting the FPR out of there.

These are sensitive to timing, too. Do you have the initial set around 10 to 12 degrees? Manifold vacuum also can make a really big difference.


Shawn
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Unread 10-02-2013, 02:30 PM   #4
teedubbaya
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Quote:
Originally Posted by Matt1981CJ7 View Post
Take the FPR off and see what it does.
Was the engine running OK before you switched carbs?
Matt
Matt, the CJ came with that carb. It was running that way before the FPR (I put on last week).

Quote:
Originally Posted by swatson454 View Post
Why don't you pull that idle jet out and see what size it is. And I agree with getting the FPR out of there.
These are sensitive to timing, too. Do you have the initial set around 10 to 12 degrees? Manifold vacuum also can make a really big difference.
Shawn
Shawn, I'll double check that timing and vac. How much vac should I be seeing? I can't remember what it was when I checked it last time.
I checked the jets last night and they are:
Pri Idle: 75
Sec Idle: 60
Both mains: 145
Pri air corr: 160
Sec air corr: 170

Thanks guys!!
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Unread 10-02-2013, 02:48 PM   #5
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Quote:
Originally Posted by teedubbaya View Post
Shawn, I'll double check that timing and vac. How much vac should I be seeing? I can't remember what it was when I checked it last time.

I checked the jets last night and they are:
Pri Idle: 75
Sec Idle: 60
Both mains: 145
Pri air corr: 160
Sec air corr: 170

Thanks guys!!
Shoot. I was hoping you had a 60 primary in there. No such luck

If it were me, I'd make sure the initial timing was at 10 degrees and the engine was fully warmed up. I wasn't clear on my post about manifold vacuum. What I should have said is that running the distributor on manifold vacuum makes a big difference. If you have an available port, I'd sure try it. The right base timing and running manifold vacuum to the distributor both serve to help you close the throttle while keeping the same idle speed.

From there, I'd back the mixture screw out to a full, 2 and a half turns out from seated. Then back the idle speed screw out all the way and then back in 1 and a half turns from contact with the linkage. At least I think that's what it is for your carb.

What that *should* do is basically swap where the engine is currently getting its fuel from the enrichment hole/s back to the idle mixture hole.

See if you can get it to hold a 500 rpm idle and slowly turn that mixture screw in and see what the engine does.

If all of that actually works, we should be able to tell if you need a different idle jet based on where your mixture screw ended up or if we might need to do a little cheating.


Shawn
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Unread 10-02-2013, 02:51 PM   #6
teedubbaya
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Thanks Shawn! I won't be able to get to it now till Friday, but I'll follow up then.
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Unread 10-02-2013, 03:06 PM   #7
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Fingers crossed!


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Unread 10-02-2013, 03:13 PM   #8
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tee,

I agree with Shawn, as usual.

It could be that your timing is too retarded, which forces you to turn the speed screw in too far to achieve a decent idle speed. What this does is rotate the throttle plate too far, exposing the primary enrichment holes. At that point, your idle is running off of the primary circuit, not the idle circuit, and it will render your idle mixture adjustment useless. I suspect any adjustment on the mixture screw has no affect on the idle, correct?

And as Shawn said, manifold vacuum to your distributer will add necessary advance and will increase your idle, which should allow you to back the speed screw out to the recommended 1-1/2 turns in. This will close the throttle plate, so that the enrichment hole is not exposed, and the mixture screw will then have the desired affect on the idle.

Good luck and report back when you have the chance to mess with it.

Matt
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Unread 10-02-2013, 03:19 PM   #9
teedubbaya
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Matt, you're right on with the idle mix screw. No real affect. It ran a *little* worse when it was out, but not a whole lot of difference, so it ended up all the way back in, then the idle speed all the way in just to keep it running.
I'm 45 years old and believe or not, this is my fist exposure to carbs. I've always had FI vehicles, so thanks for jumping on this!
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Unread 10-02-2013, 04:15 PM   #10
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There Matt goes again with his fancy graphs and such

Hey, you might want to check your plugs out before you dive into some tuning. If they've fouled with the rich mixture, your tuning efforts might not go as planned.


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Unread 10-02-2013, 05:06 PM   #11
teedubbaya
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Good point! I changed them when I got the Jeep about a month ago (they were nasty!), but I'm sure they are well fowled by now. Any recommendation on plugs?
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Unread 10-07-2013, 01:49 PM   #12
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Ok, warmed it up, checked and adjusted the timing to 10* (vac advance plugged @1600 rpm), set the carb 1.5 turns in from first contact on the idle, and backed out the idle mix 2.5 turns. I let it cool off, then started it cold. Starts up and idles high like it should, albeit, rough and puffs of black. When I kick it off high idle, it either dies when it's still kind of cold, or just barely stays running when it's warm, very rough, smoke etc.
Unfortunately, I ran out of time at that point, so haven't had any opportunity to make any other idle speed, or idle mixture changes. But it does somewhat run now without the mix and speed screws turned all the way in.
I'll follow up more on my next opportunity to work on it. It's not a DD, so it can sit till I get to it...
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Unread 10-07-2013, 02:07 PM   #13
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Ahhh, you brought something up that I believe we've neglected: the nutter bypass.

That needs to be done to pull the computer out of the loop and then your timing will be set at 10* at idle speed. This brings up another point about distributors. Yours likely has a 7 degree advance head and a replacement dizzy from a pre-81 (?) will offer a pretty big improvement in performance.

Were you able to find a port on the manifold to use for your vacuum advance?


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Unread 10-07-2013, 02:29 PM   #14
Matt1981CJ7
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I'd set the initial timing at 10* at idle speed, somewhere around 600-700 RPM.

The 1600 RPM timing adjustment is for the original computer controlled ignition and BBD carb. It does not apply to a Nuttered engine with an aftermarket carb.

edit: Quick-draw McGraw Shawn beat me to it.

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Unread 10-07-2013, 03:45 PM   #15
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What is a little "ad nauseum" without me chiming in here.

The specs Shaun gave you about the IDLE SPEED SCREW at 1 1/2 turns in maximum is correct.

Another way to get "there" is to slow the already running engine down, and readjust the timing, then again, slow the engine down and readjust the timing.
keeping the engine running is always a good thing.

The reason it is running rich "ad nauseum", and there isn't any real mixture screw adjustment is the throttle plate is open too far. Matt has a great post showing this condition.

The timing is sometimes a problem with these engines as well. Shaun say's "Yours likely has a 7 degree advance head and a replacement dizzy from a pre-81 (?) will offer a pretty big improvement in performance."

This is a big problem with these Jeeps, not enough timing.

Also, pre-ignition is cumulative damage... It all add's up to the BIG BANG. NO pinging is acceptable!!

"ad nauseum"

Good luck, plenty of good tuners here.

UPTILLNOW
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