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Old 01-15-2008, 08:57 AM   #1
DukeDKT442
 
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Default Cannister Purge Valve

So, upon pulling my carb off yesterday, I noticed that on the canister purge valve, the smallest nipple on top where the smallest diameter vacuum line attaches is broken off. So, I figured I'd just get a new one... easy enough. The old one is #17085929, with 4 hose nipples. However, when the punched in that number, they would come up with #17085928, with 5 hose nipples. #...929 doesn't exist, apparently.

If I got #...928 with the 5 nipples, and plugged the unused one, would that work, or are they different internally? Or does anyone have #...929 that they would be willing to part with?

Also, for clarification purposes... what exactly does this purge valve do, other than give me a headache?


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Last edited by DukeDKT442 : 01-15-2008 at 09:06 AM.
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Old 01-15-2008, 09:19 AM   #2
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when the coolant warms up, there is a TVS (thermal vacuum switch) that sits on the front of the intake that will supply vacuum to the purge valve, allowing the carb to draw the vapor emissions from the charcoal canister sitting in the front corner of the car.

69hurstolds had a sweet explanation on the gmail list a while back... let me see if I still have it...
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Old 01-15-2008, 09:21 AM   #3
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here is Mike's explanation from oldsgmail a while back...

Quote:
Looks like we need an "Emissions 101" course to try and join all these
thoughts together. Topic for today, EECS (Evaporative Emission Control
System). I learned PLENTY about this system when the carbon canister took a
crap on me and ended up with charcoal in the carburetor. I've discussed this
with several people in the past and there's always some mystery connected
with how this thing works and what all the lines going to the "plastic
gizmo" do.

I can only speak for V8s, so your application may be a bit different, such
as could be controlled by the ECM, or have a separate thermal fuel bowl vent
valve (V6), but all should work basically the same. G-body V8 cars do not
have ECM control or a separate fuel bowl vent valve. The charcoal canister
located in the fenderwell collects and stores fuel vapors from the tank (and
possibly carb, more on that in a bit) when the car is off.

It is open at the bottom for fresh air purge, and has one inlet and one
outlet tube on the top of it. The inlet comes from the fuel tank. The outlet
goes to the thermostatic vacuum switch (TVS) and then to the canister
control valve (CCV). It's the black plastic gizmo - about 20 bucks from GM.

The CCV has 4 tubes attached, one from the TVS, one to the carb bowl vent,
one to the carb base (smaller tube near bottom of CCV- this is where the
vapors leave to get sucked into the carb base above the butterflies, tube on
Qjet is on driver's side), as well as a diaphragm actuator vacuum tube on
the top of the CCV (normally Teed off the front of the carb body with other
line going to primary choke pulloff).

Now, here's a bit of confusing part: the outlet line of the charcoal
canister can also be the inlet for venting the carburetor fuel bowl chamber
to the canister which "holds" those vapors collected too when the car is off
AND (important part) the engine coolant temperature is above 170 degrees F.
The TVS closes off flow from the bowl vent at temps less than 170 deg. F. So
technically, the two lines on the top of the charcoal canister could both be
inlets at the same time under certain conditions. Confused yet?

I modified a portion of the emission decal to make my points here perhaps a
bit more easy to understand in the following drawings...refer to these
drawings after reading the text and see if it doesn't make a bit more sense.
Haha. Maybe if I'd learn how to spell "vacuum" in the drawings....LOL! Oh
well.

Here's what it acts like when it's running or off, and coolant temp is LESS
than 170 deg. F.
http://hurstolds.oldsgmail.com/image...essthan170.jpg

Here's how it acts when it's off and coolant temperature is greater than 170
deg. F. (like shutting it down after a run to the store):
http://hurstolds.oldsgmail.com/image...off170plus.jpg

The TVS and fuel bowl vent lines are the 3/8" lines connecting to CCV. Take
a look at your emission decal under the hood. It gives you a basic layout of
how the lines run. When the car is running at anything above idle, the EECS
sucks those vapors out and burns them through the intake normally via
smaller line to the carb, like someone else mentioned. The fuel bowl vent
part shuts off though as the CCV backseats when vacuum is applied to the top
of the CCV, allowing only the charcoal canister to vent during running
operations.

Here's how it acts when it's operating normally and coolant is greater than
170 deg. F.
http://hurstolds.oldsgmail.com/image...ing170plus.jpg

Maybe we could get this worked into the tech section....

Here's some problems I've personally experienced...

The canister control valve diaphragm gets old and pukes after a time,
rendering them useless and also a big vacuum leak. BAD and PITA to find.

The TVS on the intake pops its top. It has a spring inside and the cap is
plastic, and just glued in place. The TVS is buried behind the A/C
compressor and nearly out of sight, so a cracked or missing lid/guts can be
difficult to see depending on how much junk you have in the way. Once this
happens, HUGE vacuum leak when running. It will affect the car's
performance.

My problem on the 84 H/O was that the membrane holding the charcoal inside
the canister popped and allowed the system to suck up charcoal through the
TVS, CCV, and into the carb. VERY not good. It plugged up everything and was
a huge PITA to clean out all of it. A new charcoal canister went into place,
and all was right with the world again.
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Old 01-15-2008, 10:00 AM   #4
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WOW! That guy knows WTF he's talking about...

Part number 17085929 still showing good. $55 and change list price. Ouch. $39.86 shipped from GMPD.

Delco number is 214-542

www.oehq.com shows them in stock, their price (subject to change) is $20.98

Rockauto.com shows them for $19.69

5% off discount code good through March 11 --> 890311641309

Your call. Looks like they're still available to me.

That 928 number is for a 1984 4 cylinder Toro, and has about the same use, but their port tap angles are off compared to the V8 version.
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Old 01-15-2008, 10:52 AM   #5
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Ordered. Muchas gracias amigos!
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