Vacuum temp switch to vapor canister hose
October 6th, 2012, 12:58 AM
#1
Registered User
Thread Starter
Vacuum temp switch to vapor canister hose
1985, with a 307
There is a thermal vacuum switch with two ports. The top port has a hose from the carb to the switch with a round plastic thing between the two. The other hose is on the bottom port and goes from the switch to a canister (I'm guessing this is a vapor can with two ports "carb" and "tank")
The hose from the switch to the can keeps falling off. It's all frayed and torn on the end. The car has rough idle. Heavy gas fumes, more now that its getting cooler outside.
Car still has some emission stuff, but it's not working. Classic tags = no emission testing.
Can I plug up this port on the vacuum switch and be OK? What about removing the switch from the manifold and pluging the port on the carb?
Car runs great. I think my secondaries are sticking a bit, but that's another story
There is a thermal vacuum switch with two ports. The top port has a hose from the carb to the switch with a round plastic thing between the two. The other hose is on the bottom port and goes from the switch to a canister (I'm guessing this is a vapor can with two ports "carb" and "tank")
The hose from the switch to the can keeps falling off. It's all frayed and torn on the end. The car has rough idle. Heavy gas fumes, more now that its getting cooler outside.
Car still has some emission stuff, but it's not working. Classic tags = no emission testing.
Can I plug up this port on the vacuum switch and be OK? What about removing the switch from the manifold and pluging the port on the carb?
Car runs great. I think my secondaries are sticking a bit, but that's another story
October 8th, 2012, 04:59 PM
#2
Registered User
Join Date: Jan 2009
Location: Lehigh County Pennsylvania
Posts: 679
Would it be easier to just replace the hose that is falling off?
I have come across the same problem in my 1980 Cutlass. Just cutting off about 1 inch of the old hose and it goes back on snug.
I have come across the same problem in my 1980 Cutlass. Just cutting off about 1 inch of the old hose and it goes back on snug.
October 8th, 2012, 06:10 PM
#3
Registered User
Join Date: Jan 2010
Posts: 1,956
Maybe this can help. Lifted fom Oldspower.com. BTW, the GM part number for the canister control valve is 17085929. The temperature switch on the manifold water passage to control it is part number 22536551.
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.
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.
Last edited by 69HO43; October 8th, 2012 at 06:26 PM.
November 17th, 2013, 07:41 PM
#5
Registered User
Join Date: Aug 2013
Location: North Jersey
Posts: 28
I don't really know how to post things yet ( I hope this shows up in the right spot on this thread) but the write up by 69HO43 about the canister is right on. I have an '80 Cutlass - V6 with a little different set up but the idea is the same. I too had a messed up top filter but I couldn't find a replacement canister so I rebuilt the old one....you can find that story in the Newbie forum, written by me. It worked...I think...
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