C3 smog pump problem

1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
into the smog pump got so hot it fried. Replaced it, and it took about five
miles for it to happen again. So, I did some looking for a problem. There
is a vacuum tube (3/16") that goes out of the smog attachment to a "Y" where
part of it goes to the top of the thermostat housing and the other half goes
to the carb. Where it attached to the smog pump, it was fried and the tube
was plugged.

This is the tough part. The tube was providing vacuum I could feel with my
finger. But, the fitting fried where it attached to the smog device, so I
can't tell exactly what was on the end. Inside the tube was part of a 3/16"
fitting, but when I replaced that with a coupler, it was too small for the
hole in the smog pump.

When I looked further by shining a small light through one of the "breather"
holes (air comes out of them), I'd swear the whole thing was empty.

Let me clarify. I've been saying "smog pump" but the place I'm talking
about actually is something that attaches to the pump, not the pump itself.
Napa only showed the pump, so I don't know what the attachment is called.
It is held onto the back of the pump by two bolts, and it comes off the pump
going sideways. Both the 3/16 vacuum line and the 5/8 line from the exhaust
manifold hook into this attachment which is connected to the smog pump.

What I'm wondering is if anyone can help me with any of these questions:
1) What type of fitting is supposed to be on the 3/16 hose that will hold
firmly to the hole where it's supposed to go?
2) Is the doodad that it's supposed to go to supposed to be "empty?" Seems
an odd place to terminate a vacuum hose.
3)What the hell is that part called that attaches to the back of the pump
and that all the hoses go into?
4)Since it bolts on, can it be bought separately? The reason I'm asking
that one is because three places I checked have the pump, but not the part
of the unit I need. (That's why I still don't know what to call it, too.)
5)I've Googled til I'm dizzy, so if someone can just save me a few hours by
pointing in the right direction, that would be great.

Thanks in advance for any assistance.

(Oh, California car, so has to pass smog or I'd trash it. The State just
froze the "smog no longer required" parameters at 1977, so unless that law
is repealed, this car will need to be smogged forever.)

--
'71 Trans Am 455 H.O.
'77 Corvette coupe

B Dragon wrote:
> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
> into the smog pump got so hot it fried. Replaced it, and it took about five
> miles for it to happen again. So, I did some looking for a problem. There
> is a vacuum tube (3/16") that goes out of the smog attachment to a "Y" where
> part of it goes to the top of the thermostat housing and the other half goes
> to the carb. Where it attached to the smog pump, it was fried and the tube
> was plugged.
>
> This is the tough part. The tube was providing vacuum I could feel with my
> finger. But, the fitting fried where it attached to the smog device, so I
> can't tell exactly what was on the end. Inside the tube was part of a 3/16"
> fitting, but when I replaced that with a coupler, it was too small for the
> hole in the smog pump.
>
> When I looked further by shining a small light through one of the "breather"
> holes (air comes out of them), I'd swear the whole thing was empty.
>
> Let me clarify. I've been saying "smog pump" but the place I'm talking
> about actually is something that attaches to the pump, not the pump itself.
> Napa only showed the pump, so I don't know what the attachment is called.
> It is held onto the back of the pump by two bolts, and it comes off the pump
> going sideways. Both the 3/16 vacuum line and the 5/8 line from the exhaust
> manifold hook into this attachment which is connected to the smog pump.
>
> What I'm wondering is if anyone can help me with any of these questions:
> 1) What type of fitting is supposed to be on the 3/16 hose that will hold
> firmly to the hole where it's supposed to go?
> 2) Is the doodad that it's supposed to go to supposed to be "empty?" Seems
> an odd place to terminate a vacuum hose.
> 3)What the hell is that part called that attaches to the back of the pump
> and that all the hoses go into?
> 4)Since it bolts on, can it be bought separately? The reason I'm asking
> that one is because three places I checked have the pump, but not the part
> of the unit I need. (That's why I still don't know what to call it, too.)
> 5)I've Googled til I'm dizzy, so if someone can just save me a few hours by
> pointing in the right direction, that would be great.
>
> Thanks in advance for any assistance.
>
> (Oh, California car, so has to pass smog or I'd trash it. The State just
> froze the "smog no longer required" parameters at 1977, so unless that law
> is repealed, this car will need to be smogged forever.)
>


Maybe this site will help (click on "smog - system, pump, hoses.... etc")
http://www.docrebuild.com/dr-r-web/INDEX-S.HTML

Here's another site that might help:
http://www.cranescorvette.com/crane_...smog_parts.htm

And here's a few more vendors that might have pertinent parts:
Goat Hill Classics 714-548-6367
Bill Hodel 330-832-0871
Greenhoes 330-723-0899

B Dragon wrote:
> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
> into the smog pump got so hot it fried. Replaced it, and it took about five
> miles for it to happen again. So, I did some looking for a problem. There
> is a vacuum tube (3/16") that goes out of the smog attachment to a "Y" where
> part of it goes to the top of the thermostat housing and the other half goes
> to the carb. Where it attached to the smog pump, it was fried and the tube
> was plugged.
>
> This is the tough part. The tube was providing vacuum I could feel with my
> finger. But, the fitting fried where it attached to the smog device, so I
> can't tell exactly what was on the end. Inside the tube was part of a 3/16"
> fitting, but when I replaced that with a coupler, it was too small for the
> hole in the smog pump.
>
> When I looked further by shining a small light through one of the "breather"
> holes (air comes out of them), I'd swear the whole thing was empty.
>
> Let me clarify. I've been saying "smog pump" but the place I'm talking
> about actually is something that attaches to the pump, not the pump itself.
> Napa only showed the pump, so I don't know what the attachment is called.
> It is held onto the back of the pump by two bolts, and it comes off the pump
> going sideways. Both the 3/16 vacuum line and the 5/8 line from the exhaust
> manifold hook into this attachment which is connected to the smog pump.
>
> What I'm wondering is if anyone can help me with any of these questions:
> 1) What type of fitting is supposed to be on the 3/16 hose that will hold
> firmly to the hole where it's supposed to go?
> 2) Is the doodad that it's supposed to go to supposed to be "empty?" Seems
> an odd place to terminate a vacuum hose.
> 3)What the hell is that part called that attaches to the back of the pump
> and that all the hoses go into?
> 4)Since it bolts on, can it be bought separately? The reason I'm asking
> that one is because three places I checked have the pump, but not the part
> of the unit I need. (That's why I still don't know what to call it, too.)
> 5)I've Googled til I'm dizzy, so if someone can just save me a few hours by
> pointing in the right direction, that would be great.
>
> Thanks in advance for any assistance.
>
> (Oh, California car, so has to pass smog or I'd trash it. The State just
> froze the "smog no longer required" parameters at 1977, so unless that law
> is repealed, this car will need to be smogged forever.)
>


Maybe this site will help (click on "smog - system, pump, hoses.... etc")
http://www.docrebuild.com/dr-r-web/INDEX-S.HTML

Here's another site that might help:
http://www.cranescorvette.com/crane_...smog_parts.htm

And here's a few more vendors that might have pertinent parts:
Goat Hill Classics 714-548-6367
Bill Hodel 330-832-0871
Greenhoes 330-723-0899

The part that bolts onto the back of the AIR pump is the diverter valve.
If it is burning up, it means that one or both of the check valves is
bad. The check valves are the fittings on the manifold tube assemblies
that the 5/8" hoses attach to. They are supposed to prevent the hot
exhaust gasses from getting back up to the diverter valve.

If you find a parts store that carries Standard Ignition, the diverter
valve is part # DV-89 and the check valves are part # AV-7. You can go
to smpcorp.com and check out Parts Look Up. It is an on-line catalog,
and if you click on most of the part #s you will see a picture of the
part. Unfortunately, the DV-89 is one of the parts without a picture.


Mark

B Dragon wrote:
> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
> into the smog pump got so hot it fried. Replaced it, and it took about five
> miles for it to happen again. So, I did some looking for a problem. There
> is a vacuum tube (3/16") that goes out of the smog attachment to a "Y" where
> part of it goes to the top of the thermostat housing and the other half goes
> to the carb. Where it attached to the smog pump, it was fried and the tube
> was plugged.
>
> This is the tough part. The tube was providing vacuum I could feel with my
> finger. But, the fitting fried where it attached to the smog device, so I
> can't tell exactly what was on the end. Inside the tube was part of a 3/16"
> fitting, but when I replaced that with a coupler, it was too small for the
> hole in the smog pump.
>
> When I looked further by shining a small light through one of the "breather"
> holes (air comes out of them), I'd swear the whole thing was empty.
>
> Let me clarify. I've been saying "smog pump" but the place I'm talking
> about actually is something that attaches to the pump, not the pump itself.
> Napa only showed the pump, so I don't know what the attachment is called.
> It is held onto the back of the pump by two bolts, and it comes off the pump
> going sideways. Both the 3/16 vacuum line and the 5/8 line from the exhaust
> manifold hook into this attachment which is connected to the smog pump.
>
> What I'm wondering is if anyone can help me with any of these questions:
> 1) What type of fitting is supposed to be on the 3/16 hose that will hold
> firmly to the hole where it's supposed to go?
> 2) Is the doodad that it's supposed to go to supposed to be "empty?" Seems
> an odd place to terminate a vacuum hose.
> 3)What the hell is that part called that attaches to the back of the pump
> and that all the hoses go into?
> 4)Since it bolts on, can it be bought separately? The reason I'm asking
> that one is because three places I checked have the pump, but not the part
> of the unit I need. (That's why I still don't know what to call it, too.)
> 5)I've Googled til I'm dizzy, so if someone can just save me a few hours by
> pointing in the right direction, that would be great.
>
> Thanks in advance for any assistance.
>
> (Oh, California car, so has to pass smog or I'd trash it. The State just
> froze the "smog no longer required" parameters at 1977, so unless that law
> is repealed, this car will need to be smogged forever.)
>

The part that bolts onto the back of the AIR pump is the diverter valve.
If it is burning up, it means that one or both of the check valves is
bad. The check valves are the fittings on the manifold tube assemblies
that the 5/8" hoses attach to. They are supposed to prevent the hot
exhaust gasses from getting back up to the diverter valve.

If you find a parts store that carries Standard Ignition, the diverter
valve is part # DV-89 and the check valves are part # AV-7. You can go
to smpcorp.com and check out Parts Look Up. It is an on-line catalog,
and if you click on most of the part #s you will see a picture of the
part. Unfortunately, the DV-89 is one of the parts without a picture.


Mark

B Dragon wrote:
> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
> into the smog pump got so hot it fried. Replaced it, and it took about five
> miles for it to happen again. So, I did some looking for a problem. There
> is a vacuum tube (3/16") that goes out of the smog attachment to a "Y" where
> part of it goes to the top of the thermostat housing and the other half goes
> to the carb. Where it attached to the smog pump, it was fried and the tube
> was plugged.
>
> This is the tough part. The tube was providing vacuum I could feel with my
> finger. But, the fitting fried where it attached to the smog device, so I
> can't tell exactly what was on the end. Inside the tube was part of a 3/16"
> fitting, but when I replaced that with a coupler, it was too small for the
> hole in the smog pump.
>
> When I looked further by shining a small light through one of the "breather"
> holes (air comes out of them), I'd swear the whole thing was empty.
>
> Let me clarify. I've been saying "smog pump" but the place I'm talking
> about actually is something that attaches to the pump, not the pump itself.
> Napa only showed the pump, so I don't know what the attachment is called.
> It is held onto the back of the pump by two bolts, and it comes off the pump
> going sideways. Both the 3/16 vacuum line and the 5/8 line from the exhaust
> manifold hook into this attachment which is connected to the smog pump.
>
> What I'm wondering is if anyone can help me with any of these questions:
> 1) What type of fitting is supposed to be on the 3/16 hose that will hold
> firmly to the hole where it's supposed to go?
> 2) Is the doodad that it's supposed to go to supposed to be "empty?" Seems
> an odd place to terminate a vacuum hose.
> 3)What the hell is that part called that attaches to the back of the pump
> and that all the hoses go into?
> 4)Since it bolts on, can it be bought separately? The reason I'm asking
> that one is because three places I checked have the pump, but not the part
> of the unit I need. (That's why I still don't know what to call it, too.)
> 5)I've Googled til I'm dizzy, so if someone can just save me a few hours by
> pointing in the right direction, that would be great.
>
> Thanks in advance for any assistance.
>
> (Oh, California car, so has to pass smog or I'd trash it. The State just
> froze the "smog no longer required" parameters at 1977, so unless that law
> is repealed, this car will need to be smogged forever.)
>

B Dragon spoke thusly:

> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
> into the smog pump got so hot it fried. Replaced it, and it took about five
>

What you're talking about is called the diverter valve. What it's
supposed to do is shut off (or "divert") the air flow going to the
exhaust manifolds during decel to avoid backfiring. The vacuum hose
provides the "signal" to the DV to divert the air flow when the vacuum
is high (decel). Those hoses aren't "feedback", they are supposed to
provide the air flow to the manifolds. There are one way check valves
that are supposed to block the exhaust gases from being forced up
through the air lines. At least one of your check valves is stuck open,
letting the exhaust go up the tubes and burning up the hoses. Good luck
finding a new DV...I've been trying for a while. I've been quoted up to
$750 for a NOS one. I solved the problem with my defective DV by being
a bit "creative" and you can't tell by looking at it that it's no longer
functional.

--

Shut up, Dave.

-|>|- Diode -|<|-
'68 L-79 Coupe
'79 Triumph Bonneville

B Dragon spoke thusly:

> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
> into the smog pump got so hot it fried. Replaced it, and it took about five
>

What you're talking about is called the diverter valve. What it's
supposed to do is shut off (or "divert") the air flow going to the
exhaust manifolds during decel to avoid backfiring. The vacuum hose
provides the "signal" to the DV to divert the air flow when the vacuum
is high (decel). Those hoses aren't "feedback", they are supposed to
provide the air flow to the manifolds. There are one way check valves
that are supposed to block the exhaust gases from being forced up
through the air lines. At least one of your check valves is stuck open,
letting the exhaust go up the tubes and burning up the hoses. Good luck
finding a new DV...I've been trying for a while. I've been quoted up to
$750 for a NOS one. I solved the problem with my defective DV by being
a bit "creative" and you can't tell by looking at it that it's no longer
functional.

--

Shut up, Dave.

-|>|- Diode -|<|-
'68 L-79 Coupe
'79 Triumph Bonneville

WayneC wrote:
> B Dragon wrote:
>
>> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
>> into the smog pump got so hot it fried. Replaced it, and it took
>> about five
>> miles for it to happen again. So, I did some looking for a problem.
>> There
>> is a vacuum tube (3/16") that goes out of the smog attachment to a "Y"
>> where
>> part of it goes to the top of the thermostat housing and the other
>> half goes
>> to the carb. Where it attached to the smog pump, it was fried and the
>> tube
>> was plugged.
>>
>> This is the tough part. The tube was providing vacuum I could feel
>> with my
>> finger. But, the fitting fried where it attached to the smog device,
>> so I
>> can't tell exactly what was on the end. Inside the tube was part of a
>> 3/16"
>> fitting, but when I replaced that with a coupler, it was too small for
>> the
>> hole in the smog pump.
>>
>> When I looked further by shining a small light through one of the
>> "breather"
>> holes (air comes out of them), I'd swear the whole thing was empty.
>>
>> Let me clarify. I've been saying "smog pump" but the place I'm talking
>> about actually is something that attaches to the pump, not the pump
>> itself.
>> Napa only showed the pump, so I don't know what the attachment is called.
>> It is held onto the back of the pump by two bolts, and it comes off
>> the pump
>> going sideways. Both the 3/16 vacuum line and the 5/8 line from the
>> exhaust
>> manifold hook into this attachment which is connected to the smog pump.
>>
>> What I'm wondering is if anyone can help me with any of these questions:
>> 1) What type of fitting is supposed to be on the 3/16 hose that will hold
>> firmly to the hole where it's supposed to go?
>> 2) Is the doodad that it's supposed to go to supposed to be "empty?"
>> Seems
>> an odd place to terminate a vacuum hose.
>> 3)What the hell is that part called that attaches to the back of the pump
>> and that all the hoses go into?
>> 4)Since it bolts on, can it be bought separately? The reason I'm asking
>> that one is because three places I checked have the pump, but not the
>> part
>> of the unit I need. (That's why I still don't know what to call it,
>> too.)
>> 5)I've Googled til I'm dizzy, so if someone can just save me a few
>> hours by
>> pointing in the right direction, that would be great.
>>
>> Thanks in advance for any assistance.
>>
>> (Oh, California car, so has to pass smog or I'd trash it. The State just
>> froze the "smog no longer required" parameters at 1977, so unless that
>> law
>> is repealed, this car will need to be smogged forever.)
>>
>
>
> Maybe this site will help (click on "smog - system, pump, hoses.... etc")
> http://www.docrebuild.com/dr-r-web/INDEX-S.HTML
>
> Here's another site that might help:
> http://www.cranescorvette.com/crane_...smog_parts.htm
>
> And here's a few more vendors that might have pertinent parts:
> Goat Hill Classics 714-548-6367
> Bill Hodel 330-832-0871
> Greenhoes 330-723-0899
The Dr Rebuild catalog I referenced above does show a diverter valve for
a 77... now, whether they actually do have them may be another story.

WayneC wrote:
> B Dragon wrote:
>
>> 1977 Coupe, new 350ci. The hose that goes from the exhaust feedback tube
>> into the smog pump got so hot it fried. Replaced it, and it took
>> about five
>> miles for it to happen again. So, I did some looking for a problem.
>> There
>> is a vacuum tube (3/16") that goes out of the smog attachment to a "Y"
>> where
>> part of it goes to the top of the thermostat housing and the other
>> half goes
>> to the carb. Where it attached to the smog pump, it was fried and the
>> tube
>> was plugged.
>>
>> This is the tough part. The tube was providing vacuum I could feel
>> with my
>> finger. But, the fitting fried where it attached to the smog device,
>> so I
>> can't tell exactly what was on the end. Inside the tube was part of a
>> 3/16"
>> fitting, but when I replaced that with a coupler, it was too small for
>> the
>> hole in the smog pump.
>>
>> When I looked further by shining a small light through one of the
>> "breather"
>> holes (air comes out of them), I'd swear the whole thing was empty.
>>
>> Let me clarify. I've been saying "smog pump" but the place I'm talking
>> about actually is something that attaches to the pump, not the pump
>> itself.
>> Napa only showed the pump, so I don't know what the attachment is called.
>> It is held onto the back of the pump by two bolts, and it comes off
>> the pump
>> going sideways. Both the 3/16 vacuum line and the 5/8 line from the
>> exhaust
>> manifold hook into this attachment which is connected to the smog pump.
>>
>> What I'm wondering is if anyone can help me with any of these questions:
>> 1) What type of fitting is supposed to be on the 3/16 hose that will hold
>> firmly to the hole where it's supposed to go?
>> 2) Is the doodad that it's supposed to go to supposed to be "empty?"
>> Seems
>> an odd place to terminate a vacuum hose.
>> 3)What the hell is that part called that attaches to the back of the pump
>> and that all the hoses go into?
>> 4)Since it bolts on, can it be bought separately? The reason I'm asking
>> that one is because three places I checked have the pump, but not the
>> part
>> of the unit I need. (That's why I still don't know what to call it,
>> too.)
>> 5)I've Googled til I'm dizzy, so if someone can just save me a few
>> hours by
>> pointing in the right direction, that would be great.
>>
>> Thanks in advance for any assistance.
>>
>> (Oh, California car, so has to pass smog or I'd trash it. The State just
>> froze the "smog no longer required" parameters at 1977, so unless that
>> law
>> is repealed, this car will need to be smogged forever.)
>>
>
>
> Maybe this site will help (click on "smog - system, pump, hoses.... etc")
> http://www.docrebuild.com/dr-r-web/INDEX-S.HTML
>
> Here's another site that might help:
> http://www.cranescorvette.com/crane_...smog_parts.htm
>
> And here's a few more vendors that might have pertinent parts:
> Goat Hill Classics 714-548-6367
> Bill Hodel 330-832-0871
> Greenhoes 330-723-0899
The Dr Rebuild catalog I referenced above does show a diverter valve for
a 77... now, whether they actually do have them may be another story.

Wayne, Mark and Diode. Thanks. You are all right on the money. In fact,
thanks a whole lot. I missed Dr. Rebuild's closing time by five minutes, so
I will call him tomorrow (grumpy sounding *******, isn't he?) and hope he's
got the diverter. And, I'm checking for Standard Ignition.

I suppose I need (or might as well) replace the diverter valve and the check
valves if they are available. Seems like usually when one thing gives way,
the rest are soon to follow.

Diode, I'd love to be creative in the solution as well, but since the car
needs to pass smog, I don't suppose I can be.

Thanks again. I'll let you know how it turns out both for availability and
cost.