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Guest Message by DevFuse
 

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1987 Thermo Vaccum Valve/Switch ports?


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9 replies to this topic

#1 kanurys

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Posted 09 September 2010 - 05:48 PM

I have a vac diagram under my hood that is not helpful, since I don't have all that stuff on there anymore. It's weberized, too, and doesn't have the Christmas tree of hard lines and other extraneous vacuum crap that came with the hitachi.

Question: What components do the ports on the Thermo Vacuum switch terminate at? Which ports exactly on the thermo vac switch?

I've done a lot of research on this, but can't find anything specific enough to say, for example, the top port leads to the egr, middle to the charcoal canister and bottom to the carb egr port, or what ever it is. I'm looking for a definitive vac signal path please. Thanks.

#2 Seantheimpaler

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Posted 09 September 2010 - 06:07 PM

Posted Image
Posted Image
Posted Image

Does one of these help?

#3 kanurys

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Posted 09 September 2010 - 06:15 PM

Dude, sweet scans. And yes, that is exactly what I needed. My Haynes doesn't have ea82's and my FSM pdf is missing the carb section. Thank you.

#4 Seantheimpaler

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Posted 09 September 2010 - 06:17 PM

no problemo!

#5 kanurys

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Posted 09 September 2010 - 06:32 PM

Verify me on this, folks:

When Cold:
The thermo vacuum switch bleeds air from the air cleaner into the egr and timing advance nodes of vacuum, effectively reducing the vacuum in those respective lines, keeping egr closed and 0 advance on the ignition timing. At these nodes supplying vac to the egr and distributor, the respective vac lines from thermo vac switch are t-ed in. Another effect of the air bleeding in is it leans out the air/fuel mixture a little while the choke is closed.

When Hot:
No air can flow in or out of any of the ports on the thermo vac switch and the egr valve sees vac signal when it's supposed to and the disty advance sees vac when it's supposed to. No air is bleeds into the intake or bypasses the throttle plate.

How did I do?

Thanks for the pics, again. I always thought it was the other way around, the switch just cut off the vac supply. Instead it nullifies it. Cool.

#6 Seantheimpaler

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Posted 09 September 2010 - 06:47 PM

TVV is closed below 59 degrees F, it opens from 59 to 95 degrees F and then closes again at temperatures exceeding 95 degrees F...

#7 kanurys

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Posted 10 September 2010 - 12:15 AM

Nice. Also helpful information. Thanks. I'll post pictures regarding how my routing turned out.

#8 kanurys

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Posted 10 September 2010 - 12:30 AM

Here's the vac switch all hooked up:
Posted Image

Above, you can see where the EGR is T-ed into the valve. Below, underneath everything you can see where the distributor advance is T-ed in to the valve.
Posted Image

I got fresh air from the hose that goes from the pcv system to the air cleaner:
Posted Image

Thanks for all the advice you guys threw my way.



Posted Image

Edited by kanurys, 10 September 2010 - 12:35 AM.


#9 Seantheimpaler

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Posted 10 September 2010 - 03:13 PM

that's nice and clean! I'm gonna do that to my ea81 w/hitachi just to make it easier to work on!

#10 kanurys

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Posted 10 September 2010 - 03:59 PM

that's nice and clean! I'm gonna do that to my ea81 w/hitachi just to make it easier to work on!


A little engine degreaser goes a long ways. Also an almost complete rebuild makes the degreasing easier. Here's a link to my process: http://www.ultimates...ad.php?t=114817

Oh, and ditch that hitachi for a weber. That will clean a huge mess of vac lines and wires up.




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