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28 PCI Disassembly/Running Issues
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my59
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PostPosted: Mon Oct 11, 2010 11:06 am    Post subject: Reply with quote

Have you checked for leaks at the throttle shaft? How much slop in the throttle butterfly? The shaft might seal at idle and then leak when rotated. Crank up the engine and spray throttle shaft ends with wd-40. If car runs better (is no air being pulled in) before WD-40 goes away you have a leak there.
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my59: Well son, my grandfather died before I got to drive it, so does that answer your question?
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rayvwbug
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PostPosted: Mon Oct 11, 2010 4:59 pm    Post subject: Reply with quote

So a few more updates:
1. Found a 180 air correction jet in the original carb the owner supplied in a box of old parts when I got the car. Removed the 195, checked for cracks in the housing, and finding none, installed the 180. Much better, but still a bit lean after shifts. Popped once while accelerating after a shift, still bogs some, so it still seems lean.
2. Throttle shafts seem tight.
3. Reran some warm tests. Compression as follows 100,95,90, 110. With engine warm, but not hot I had oil pressures at 30 idle, 45 on fast idle. Seems the engine may be healthier than I thought or is that too wide a range? Is there a good additive out there to clean up the interior of the engine? I can plan to remove and clean the exterior of the engine over the winter.

Since smaller air jet made such a difference, I will try to see if there is anything else that would have it lean out as much as it does. I welcome any and all opinions.

Ray
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Snort
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PostPosted: Mon Oct 11, 2010 5:38 pm    Post subject: Reply with quote

Here is a clip from the Bentley Manual regarding jets, should you find a need for it.
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sunroof
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PostPosted: Mon Oct 11, 2010 6:48 pm    Post subject: Reply with quote

Here's a stupid question: is your venturi in right side up? If it is upside down you will get a lean mixture in your high speed circuit.
Also: I had a carb where the air correction jet was broken right off, I could not tell from the way the engine ran that it was gone. I was diagnosing a plugged accelerator pump when I noticed it. My understanding is that the air correction jet bleeds a calibrated amount of air into the fuel from the main jet, leaning the mixture out as the velocity of the air thru the venturi increases. Without the air correction jet you get an overly rich mixture which can cause a poor idle and poor performance just off idle. Read "can" since technically the high speed circuit is not engaged at and just off idle. Try removing the air correction jet altogether and see what happens.

Don
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rayvwbug
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PostPosted: Mon Oct 11, 2010 7:34 pm    Post subject: Reply with quote

The air correction jet is definitely there as I swapped it earlier today based on advice from another poster. Swapped from 195 to 180 so it would be less air and it helped. The venturi is in correctly as I did look at that sometime ago. Not sure how to even get it out as my carb does not have the typical retaining screw.
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66 dormi
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PostPosted: Mon Oct 11, 2010 8:22 pm    Post subject: Reply with quote

I just went through this on Saturday ran fine and bogged down and died on acceleration then if I used the choke I could barely keep it running swap Laughing ped the carb out and all is fine!
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my59
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PostPosted: Mon Oct 11, 2010 8:46 pm    Post subject: Reply with quote

The venturi just sits in the carb and you can fish it out with a finger.

When the carb is on the car, is it set up right?

The manual has a detail about setting the pedal cable up to reduce strain on the cable. You open the throttle valve so there is 1 mm (.04") clearance between the throttle lever and the stop on the carb and then fully depress the pedal before tightening the set screw.

Is the idle set right? Hows the tip on the volume control screw?
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my59: Well son, my grandfather died before I got to drive it, so does that answer your question?
our79: sunroof bus w/camper interior and 2.0 FI
Other:'12 Jetta, '77 Benz 300D, and a 74 MG Midget.
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skyto
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PostPosted: Tue Sep 27, 2011 12:41 am    Post subject: Reply with quote

I'll add my venturi removal hell here. The old one was stuck. I tried
- hot/cold treatment
- carb cleaner,
- acetone,
- WD40
- held the carb by the id of the vent with snap ring pliers & hammered the carb body with rubber mallet
- tapping with screwdriver

The srcrewdriver method just damaged the bottom edge and certainly made things even worse. It finally came out very easy with these M6 size bolts, nuts and washers (one with filed sides to slip in and grab the vent). The tube part is a sprinkler fitting.
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henry roberts
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PostPosted: Tue Sep 27, 2011 1:55 am    Post subject: Reply with quote

i think i love you... i was looking at a PCI with a stuck venturi last night and wondering how the hell to get it out.
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skyto
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PostPosted: Sat Oct 08, 2011 7:51 am    Post subject: Reply with quote

First thing is to remove the emulsion tube carrier. These are a tight fit, they have M6 threads for the air correction jet. I used the same size bolt to lift it up.

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Here I used another venturi as a tool, with hockey stick tape to avoid scratches.
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It's important not to thread the bolt in tight - the tube carrier tip may break off. While turning the nut the bolt shouldn't turn at all.
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747frieghtdog
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PostPosted: Wed Jul 24, 2013 11:00 pm    Post subject: Reply with quote

Any conclusion to this story?

I'm having same issue after swapping one 28pci for another.

So the stumbling is associated with the current carb on the motor as soon as I installed it, where the other 28pci ran beautifully but had to remove it, long story.
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rayvwbug
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PostPosted: Thu Feb 04, 2016 10:43 am    Post subject: Re: 28 PCI Disassembly/Running Issues Reply with quote

Just saw the followup question at the end of this thread when Everett suggested it to another poster. I have only driven the car sporadically in the last few years due to health issues, but I found the more I drove it, the better it ran. I suspect a combination of older fuel and perhaps dizzy stickiness contributed.

Ray
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Bluemanx212
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PostPosted: Thu Feb 04, 2016 1:26 pm    Post subject: Re: 28 PCI Disassembly/Running Issues Reply with quote

Gas is cheap right now use it in your mower drain the tank and add some fresh fuel to eliminate that problem. Especially if the other carb is doing similar things. Have seen a few cars over the years run like new with just a fresh tank of gas that were running poorly before! If the stumble continues good luck with your problem!
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