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1500S distributor

>I've got a problem. No, no, no, not that kind of a problem, there are 
>other places on the net for that. The problem concerns the distributor of 
>my 1500S engine. It's a Bosch, ZV/JCU 4 R 3 which has both a 
>mechanical and vacuum advance, and according to Aaron it's correct for a 
>pre aug '64 wich makes sense. The vacuum advance doesn't work anymore and 
>I've tried to take it apart but couldn't figure out how to fix it. It 
>doesn't look like any vacuum advance I've ever seen, on the body it says: 
>413 and 81. At the side where the vacuum tube goes in there is a 
>hexagonal bit (17mm) sticking out with a  17 mm bold to close it off. If 
>I unscrew that there's a screw but I can't screw it out only a bit in and 
>how can I fix it, how does it work, and can I use another vacuum advance, 
>if so which one or do they all fit. I'd like to keep the distributor, 
>like not replace it with a 009 or later model.

Sorry, this is a bit too early to be in my immediate realm of experience, 
but I suspect that you could replace the vacuum advance canister with a 
later one.  The ones I'm familiar with all have the same mounting scheme.  
The 065 unit was used from 68-71 and is still cheap and available.  

I suspect that the hex bolt is a plug to allow access to an adjustment screw 
that adjusts the total amount of travel (advance) available from the unit.  
This was probably intended to be adjusted once at the factory and then left 
alone.  Modern manufacturing techniques allow the parts to be made to the 
right settings from the start, so such adjustments are no longer needed.

On rereading your note I see that you don't say exactly why your vac advance 
no longer works.  Here's what you do to test it:  Just push a piece of hose 
on the connection pipe and suck on it.  You should be able to create a 
vacuum that persists; if the chamber leaks up to atmospheric then the 
diaphram is leaking and I don't think there is anything you can do about it.

The part number for your dist. is 341 905 205, it is #3 on the VW list.  The 
replacement vacuum advance is a 341 905 271.  Perhaps this will help you 
find an original replacement if that's what you need.

On the other hand you may just have a frozen up breaker plate in your 
distributor.  If the symptom is that the vac advance is holding vacuum and 
pulling, but nothing is moving, then you need to disassemble the 
distributor, pull apart the two breaker plate halves, use a whetstone to 
remove any burrs, then lubricate and reassemble.  A replacement breaker 
plate for your distributor is not shown in my listings.

If you're not sure about what to do, I can probably rebuild the distributor 
for you.

Good luck, I hope your advance unit is still good.

       Melissa Kepner                                    Jim Adney
       jadney@vwtype3.org              jadney@vwtype3.org
                             Laura Kepner-Adney
                             Madison, Wisconsin

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